Modified Factory Pontiac Quadrajet Intake for Square-bore FiTech Throttle Body EFI

I finally got around to modifying my factory 1972 Pontiac Quadrajet spread-bore intake to accept the square-bore FiTech throttle body EFI. The results are in, the car runs smoother than ever and I can now mount my shaker to the throttle body using the factory air cleaner base!

Modifying a Pontiac Quadrajet intake to accept a square bore throttle body

Note that these instructions are for modifying a Pontiac intake designed for a Quadrajet spread-bore carburetor. Modifying a spread-bore intake for other manufacturers will more than likely be slightly different. Please note that your intake’s runners may be positioned differently thus requiring different attention where to modify.

Modifying a factory intake is not hard and only requires a few tools. Here’s the short list of tools necessary:

  • Reciprocating saw (Sawzall) with bi-metal blades
  • WD40 (or better cutting specific oil)
  • Die grinder (powered by an air compressor recommended)
  • Carbide Burr set (you may want to use both a cylindrical shape one as well as a small ball or tree shaped one to finish off corners)

First, do not modify the intake on your vehicle! First think you need to do is remove the intake manifold. For a pontiac, this requires draining (or partially draining) the coolant enough that removing the intake does not cause drainage from the water crossover in the front of the intake. The draw-down bolt will also require you to remove at least the alternator and in my case, power steering brackets in order to access. I spent more time taking the intake manifold off and bagging/tagging everything than I did actually modifying the intake.

Modifying the intake spread bore openings

You want to make cuts with the saw to remove as much material as possible taking into consideration that some locations you do not want to remove too much material and expose the other side of the intake. Remember these intakes are dual plane and the last thing you want is to poke a hole in the wrong location!

First cuts ran along the outsides. Thes cuts clear the outer most portions of a square bore gasket.
First cuts ran along the outsides. These cuts clear the outer most portions of a square bore gasket.
The 3rd cut took place on the left side (right side if viewing from the drivers seat). This one pretty much opened the one side almost perfectly, requiring only some grinding to the secondary to clear the square bore gasket.
The 3rd cut took place on the left side (right side if viewing from the drivers seat). This one pretty much opened the one side almost perfectly, requiring only some grinding to the secondary to clear the square bore gasket.
Here you can see using a square bore 4 hole gasket that only a small section of the secondary (top right of the left secondary and top left of the right secondary) needs to be ground down for clearance. The rest of the secondary openings are fine as-is.
Here you can see using a square bore 4 hole gasket that only a small section of the secondary (top right of the left secondary and top left of the right secondary) needs to be ground down for clearance. The rest of the secondary openings are fine as-is.
The right side of the intake manifold required extra cutting through thicker material. The second cut ran between the secondary to the primary. You may skip this cut if you have a steady hand when using your Sawzall.
The right side of the intake manifold required extra cutting through thicker material. The second cut ran between the secondary to the primary. You may skip this cut if you have a steady hand when using your Sawzall.
The remaining 2 cuts I did at thhe same time. Forming a V, I cut the remaining section between the primary and secondary as close as I could along the centerline of the intake. I was careful not to remove too much material as the walls to the intake runners from the other plane are very close in this area.
The remaining 2 cuts I did at thhe same time. Forming a V, I cut the remaining section between the primary and secondary as close as I could along the centerline of the intake. I was careful not to remove too much material as the walls to the intake runners from the other plane are very close in this area.
With the die grinder carbide burrs I removed just enough material from thetop inner corners of the secondaries as well as smoothed out the areas along the center separating the planes of the intake.
With the die grinder carbide burrs I removed just enough material from thetop inner corners of the secondaries as well as smoothed out the areas along the center separating the planes of the intake.
Once I was done I test fit the square bore single opening gasket to the intake. This is the gasket I will ultimately use with the FiTech throttle body.
Once I was done I test fit the square bore single opening gasket to the intake. This is the gasket I will ultimately use with the FiTech throttle body.
I will not claim to be a porting expert. I got the job done and all of the rough edges removed, I did not spend the time to remove scratches that I may have left along the walls. You could see them but feeling with your fingernail they were essentially not existent.
I will not claim to be a porting expert. I got the job done and all of the rough edges removed, I did not spend the time to remove scratches that I may have left along the walls. You could see them but feeling with your fingernail they were essentially not existent.

Reinstall intake

Once I was done, I washed the intake 3 times then followed the normal directions for installing the intake. The only thing I do that is sometimes not mentioned in manuals is use RTV sealer round the draw down rubber washer (this is the rubber washer that a new intake manifold gasket set will come with that goes between the intake and the timing chain/water pump cover) as well as around the water crossover ports that run to the heads. I am not a big fan of over using RTV sealer, I essentially used enough that when you torque the bolts down you just see a sliver of RTV squeeze out of the mating parts. If you see gobs of RTV sealer oozing out between your parts, then I think you’re using too much.

When I set the intake in place, I just tightened the 10 bolts until they started to grab the intake. Then I torqued the draw down bolt to 15 ft/lbs. Following that I torqued the intake bolts from the center out to 15 ft/lbs, then 30 ft/lbs, then ending with 40 ft/lbs. Everything else I re-connected including the top radiator hose, fuel lines, and wiring for the FiTech.

Modified Intake Results: Shaker fits perfectly!

I can now use the factory air cleaner and shaker with the FiTech!

Shaker with factory intake and FiTech throttle bodyShaker with factory intake and FiTech throttle body

Remounting the Blaster SS Coil

During the process of pulling the intake manifold off the car and modifying it, I noticed that one of the 3 mounts for the Blaster SS Coil had ripped leaving the coil dangling in a not so desired way off of the firewall. Even tough MSD claims you can mount the Blaster SS Coil in any way you like, I determined that the rubber mounts that the Blaster SS comes with are not up to the task of holding the weight of the coil in any other direction but vertically.

At the last minute I created a new mount out of 3/16″ thick 2″ wide aluminum plate and fastened it to the choke side of the intake manifold. I am not sure I will leave it here since I think this creates too much heat in this location, but I will give it a try for a couple weeks at least.

MSD Blaster SS mounted on choke side of throttle body
MSD Blaster SS mounted on choke side of throttle body (I am aware that the throttle body does not have a choke)
The Blaster SS coil clears the air cleaner by over 1/2". This is plenty of clearance for me. My only concern is the possibility of heat build-up in this location, but it may be a good location since it is in the path of the radiator fan.
The Blaster SS coil clears the air cleaner by over 1/2″. This is plenty of clearance for me. My only concern is the possibility of heat build-up in this location, but it may be a good location since it is in the path of the radiator fan.

Custom Made Drop Base for 2nd Gen Trans Am

Last fall I made a custom drop base for my Trans Am. The drop base is needed in order to fit the shaker under the factory hood when using aftermarket parts that raise the intake flange (mounting point for carburetor/throttle body) higher than factory.

Before I go any further, I want to make it clear that I do not recommend building your own drop base. I spent about $150 on materials, an initial 8 hours making the drop base, plus endless hours afterward trying to make it work. The final product was not as I hoped. See the photos to see the results. Please consider one of the solutions I list next before making your own drop base.

Permanent drop base solution

A permanent drop base solution is to do one of the following.

  • Factory Intake – It is possible to modify a factory intake then use an adapter such as the Edelbrock 2732, assuming the carb/EFI provides mounting holes for spread-bore mounting. FiTech EFI throttle body provides such mounting holes.
  • Edelbrock Performer (not RPM) – Remember a factory Pontiac intake will more than likely outperform an Edelbrock Performer.
  • Other aftermarket factory height intake. There are some single plane intakes but if your engine is designed for dual plane I would not switch to a single plane.

Alternative drop base solutions

Get a drop base from a reputable Pontiac supplier…

All of the above solutions are a compromise. All of the above require that your shaker is cut in order to function properly.

The Airaid solution utilizes the traditional round air filter method. The good thing about this solution is that other than the drop base itself, the air filter is sealed like factory with a round air cleaner lid. The disadvantage is air turbulence created when the air first flows into the shaker, then around the air cleaner lid then through the filter. I did blow some air with a fan through the filter at angles and could not tell if it was impacting the speed of the air but I think it is a concern none the less. More importantly it puts a smaller clearance between the actual carburetor and the lid top which is restrictive. If you are running a throttle body, that clearance may not be as critical, but if you are using a quadrajet, the secondary walls may be very close to the top of the air cleaner lid.

The rectangular air filter solution requires that your shaker be modified to allow air to flow through the square filter. This solution presents the same issue as the Airaid filter in that the air flows through the filter at an angle. One advantage is the air only has to make one turn, rather than flow around a lid then up and into the carb/throttle body. The biggest drawback to this solution is sealing. Air filtration could be breached around the edges from the plate that is glued to the top of your shaker as well as from the gab between your shaker and drop base.

A solution to the problem no one produces today

One solution to this problem is a re-designed shaker. I have a few ideas but no time to make them a reality.

Another solution is to redesign a completely different air filter lid. Perhaps someone can take inspiration from the K&N filter lid I modified to build something better.

Custom drop base construction

I do not recommend building your own drop base, but for those who want to know how I built mine, here are the quick and dirty instructions.

Custom Drop Base Custom Drop Base

I used a K&N drop base #3549, a 16″ diameter 1.5″ deep pizza pan, and an Airaid #801-452 filter (14″ diameter on the bottom and 10.75″ diameter at the top), and a K&N filter lid #66-1101. I cut a hole in the pizza pan and then used bolts with rivet style heads and lock washer nuts to fasten the drop base to the pizza pan. Other than drilling holes for the rivet style bolts, I did not modify the drop base. I also modified the filter lid with a slight cut in order for it to clear the shaker.

Once I put this all together I was initially quite pleased with the results. The shaker did not rub against the filter lid with my relief cut in the filter lid which was initially my primary concern. What I did not anticipate was the shaker not fitting properly on the pizza pan because the diameter was exactly 16″ in diameter, whereas the factory air cleaner lid was actually 16-1/2″ in diameter. To compensate, I added 4 pieces of metal at four corners. This worked except it allowed the lid to slowly turn. A quick solution was then to add duct tape at each corner to provide enough friction for the top shaker not to move once the shaker ring is tightened. AS soon as I added duct tape to the assembly I realized this was not worth my time.

What I am going to do…

I am going to take the factory intake off the motor and take a grinding wheel to it! The plan is to open up the holes to allow for a square bore to be mounted directly to it with the use of a very thin adapter (Edelbrock 2732). I will post when I do this.

FiTech Throttle Body Go EFI 4 Installed in Project Trans Am

FiTech Go EFI 4 installed in a 1981 (to 1978 conversion) Trans Am was a success. Please follow the post completely for details of the process.

The results

I’ve only put 120 miles on the FiTech so far, but I have to say it’s worth every penny. I’m a geek (I write software for a living), having the ability to tweak settings from a hand held controller makes me happy. Having the LCD display providing me real time AF ratios, engine temperature and rpm at the same time is pretty sweet too. Throttle response is not delayed, I expected it to have a delay like most modern fuel injection cars do. Throttle response is as instant as a carburetor.

As fast as I can turn the key and let go is how fast it starts. No more high to low engine rev at startup, it starts and stays right at 750rpm. When I put it in gear, there’s a slight drop in rpm then it’s back up to 750rpm. I may drop the rpm’s down another 50-100 rpm once I’m satisfied with everything. Best part is, I can change this with the handheld controller.

Engine has never ran this consistently cool before. I have a 160 thermostat, usually my car would get as hot as 195. It now stays between 165-175.

So far so good! Now with the process of installing…

W72 shaker air cleaner clearance

The first thing I did when I got home was test the FiTech with my 78 shaker air cleaner. As you can see in the pictures I did not undo the wiring around the throttle body until after the test fit. Luckily it clears, but just. See the video, you can see I can just pass a sheet of paper between the drop base and the side of the FiTech where I believe the fuel return system is housed. This test was without a gasket between the throttle body and air cleaner, which has given me a touch more space since I took these pictures.

FiTech Normal Base FiTech Normal Base FiTech W72 Base FiTech W72 Base

Video: Test fit of FiTech in W72 air cleaner

Note: FiTech throttle body clears when using a 90 degree AN6 fitting for the fuel inlet and the return line is capped (you can do this when using their fuel control center). A factory air cleaner drop base (shaker air cleaner) will not clear without modification if a return line is used.

Measurements for aftermarket drop bases

I took some measurements from center to send to the Pro Touring F Body and Blocker’s Performance to see if their drop bases will clear.

So far I got a response (in less than 4 hours) from Pro Touring F body. They recommend going with their 1-1/2″ drop base, then adding a 1/2″ carb to air cleaner spacer. Doing so will provide over 3 inches of space (A) between the air cleaner ring and the outer drop edge. (see image with line markings A and B).

I believe the Blocker’s drop base will also clear. I will update this post when I get confirmation.

FiTech to max from center width FiTech to max level with air cleaner assuembly widthDrop Base MeasurementThe tightest point is the very edge of the side with the return line bulge, it’s exactly 5-1/8″ from center. The height at this point is 5/16″ higher than the air cleaner mounting ring. This is the only area where the FiTech is higher than the air cleaner mounting ring.

The maximum width from center is 5-1/2″, which is at the same height as the air cleaner mounting ring.

See the FiTech Throttle Body dimensions PDF

Any Drop base designed to fit under a Pontiac Quadrajet (which has an external vent hole at front) will easily clear this 5/16″ height above the air cleaner mounting ring. As long as measurement A is 3″ you should clear with no issues.

Mounting the FiTech to a spread bore intake

For now I took the simple approach of using an Edelbrock 2696 Square-Bore to Spread-Bore adapter. The quadrajet gasket it came with did not line up properly so I used a thin Mr Gasket quadrajet gasket to get the job done on the intake side.

FiTech Pre mount square to spread bore adapter

I am thinking about taking the factory intake off and grinding away the quadrajet holes to allow the square bore holes to feed the factory intake directly. The FiTech comes with both square and spread bore mounting holes, so it is possible to mount it directly once the intake is modified. If I do this, then I would only need an Edelbrock 2732 1/16″ thick adapter plate. Then I could keep the factory air cleaner and mount the shaker directly to it. It may also give me slightly better performance, though I am doubtful. The primary holes of a spread bore are slightly smaller than the throttle body square bore holes, which may be costing me some horse power.

If I don’t modify the intake, when I switch my hood over to a shaker hood I will have to run an aftermarket drop base. I think I decided to go this route, at least for the next year.

FiTech Go EFI 4 and Fuel Command Center

Here are pictures of the Throttle body and mounting hardware just before I installed them. I wanted to point out the quality of the materials used. The throttle body is heavy and has a very nice finish. The brackets for the fuel center are very thick and feature the FiTech wording cut into the brackets. In my case, you will never see this as I have this tucked within the core support.

FiTech Go EFI 4 FiTech Fuel Control module brackets

FiTech EFI and Fuel Command Center installed

Initial installation took 4 hours. My friend Joel (check out his Firebird) was a big help. Thanks Joel! I have since spent another 4 hours tweaking things such as a better position for the throttle bracket and rerouting the PCV line. At the moment I am using the factory 78′ w72 drop base with a 3″ air filter and a flat air cleaner lid (not ideal). This is currently under a 1981 turbo hood. Everything clears with the flat air cleaner lid.

FiTech Go EFI 4 Installed FiTech Go EFI 4 InstalledFiTech on Pontiac 400 in Trans AmFiTech on Pontiac 400 in Trans Am FiTech Go EFI 4 Installed FiTech Fuel Control Module installed FiTech Fuel Control Module installed

Video: First run with FiTech EFI system

FiTech Handheld Controller with Dashboard

I spent a good hour sitting in my car thinking about how I would permanently mount the FiTech handheld controller. I then went back to the box the system came in and grabbed their mount for the controller. I just mounted it to the window as you see in the pictures and got to thinking. I decided I’m just going to keep it portable, this way I can take it down and hide it in the glove box at times I want to clean up the view in the interior.

In the map pocket you can see I got Randy’s 3 pod map pocket gauge cluster adapter. At the moment I have AutoMeter electric oil pressure and water temperature gauges as well as an AEM air fuel ratio gauge. At the moment the temperature gauge is not hooked up because the temp sender for the FiTech took it’s place on the intake manifold. I’m on the fence on hooking this back up. I still have the temp gauge in the factory cluster as well, though it is not accurate it is at least consistently inaccurate (laugh out loud). Now I know why most modern cars with temp gauges just show a sweep without temperature numbers. As long as the FiTech can give me the engine temperature I may just remove the AutoMeter temp gauge.

FiTech EFI with dashboard FiTech EFI with dashboard FiTech EFI with dashboard

Linkage and air cleaner stud tweaks

The first day I got the FiTech installed, I ended up using a two inch 5/16″ bolt to hold down the air cleaner to get the job done and go cruising. The next day I did some hunting and found at the local Advance auto parts the part I needed, Mr Gasket 6399.

I have a 1972 factory intake. The 72 throttle bracket worked perfectly with the quadrajet, but now with the FiTech, it appears the throttle cable needs to move back about 1/8″. At first I was considering going to a 75-79 throttle bracket. When I was looking at all my intake parts in the basement I remembered the adapter that the Edelbrock Performer intake came with. That bracket ended up being perfect for 2 reasons. It raised the bracket up enough to better align with the FiTech (acts as a spacer for the throttle bracket) and it brought the 72 throttle bracket back about 1/4″.

For the transmission I used a kick down bracket from one of those cheap universal throttle cable kits and mounted it on the center of the 3 holes on the factory throttle bracket. Only thing left is to put a 1″ spacer of some sort from the throttle to mount the kick down stud to (that way the kick down clears the return spring, not installed in this picture). I am going to Jegs at lunch today to get that sorted.

Update 1: A kick down stud is on order, should be arriving in 24 hours (Jegs had to ship it from their warehouse).

FiTech Throttle modifications FiTech Throttle modifications FiTech carb stud adapter

Clearance with 81 Trans Am Turbo hood

I tested the clearance with the factory lid with the kid’s play-doh. The air cleaner lid I am using is not ideal, but for now I am running a flatter air cleaner lid to give myself about 3/4″ clearance with the hood. The factory air cleaner lid only provided about 5/16″ of clearance, which I am not comfortable with.

FiTech Hood clearance FiTech Hood clearance

W72 factory air cleaner drop base modifications

I am not a fan of permanently modifying factory parts unless I have to. With the drop base, all I needed to do was plug the inside holes. I did this with some 1/4″ machine screws and lock nuts, and two 1″ wide fender washers with a #10 machine screw and lock nut. It doesn’t look pretty but it does the job. Air can only come in through the filter.

FiTech and W72 Air CleanerFiTech and W72 Air Cleaner FiTech and W72 Air Cleaner

Tips and Suggestions

Ignition and Timing: If you want to be able to control your ignition timing with the FiTech you can. You can set the timing for 3 situations, WOT, no throttle (map sensor full vacuum) and boost (if you are running turbo, super charger, etc…). Each is set at idle, 1,100, 3,000 or 6,000 rpm. Idle rpm can be set as well. There are two setups:

  1. You can use a coil and locked out 2 wire distributor with the FiTech directly.
  2. You can use a CD box and run a single phasing wire from the FiTech to the CD box.

In both cases, you will need a coil and a 2 wire distributor.

I am running a MSD 6AL2 Programmable which has more programmable rpm points than the FiTech. If I didn’t have the 6AL2, I would more than likely get a simple CD box and a Jegs Pontiac 2 wire distributor and let the FiTech control timing.

Fuel control center installation tips: I mounted the Fuel Control Center on the core support where the vapor canister mounts. I mounted it more toward the radiator though. 3 of the 4 mounting points are flush with the core support. One mounting hole I used a 3/8″ nut as a spacer. The core support has some pressed in indents for things like the vapor canister, a 3/8″ nut seemed to have the right height to bridge that gap perfectly. The mounting hardware that comes with the Fuel Control Center worked perfectly otherwise.

If I took the time to look at all the parts before I installed the system, I would have purchased a 90 degree AN 6 elbow to attach the high pressure fuel filter directly to. Then I would only have one run of high pressure push lock hose to the throttle body. I’ve added this to the list of suggested parts below.

FiTech EFI installation tips: This was rather straight forward. In my situation I had to use a square to spread bore adapter. The adapter was great, but the gaskets it came with are not to be desired. Specifically the Quadrajet side the primary holes were not in the right spot of the gasket. To keep the gasket thin I used a mr gasket one I had from a previous purchase. If you are using a spacer like the one I got that adds .8″ height, you want to use the thinnest gaskets possible (avoid the factory 1/4″ hardboard quadrajet gasket if possible).

Parts List

Stuff anyone will need:

  • FiTech 30002 Go EFI 4
  • FiTech 40003 Fuel Control Module
  • Four 3/8″ hose low pressure fuel line clamps
  • Five feet of 3/8″ low pressure fuel line hose
  • Fram G15 inline fuel filter
  • -6 AN 90 degree coupler fitting to bolt fuel filter directly to coupler (or one -6 AN 90 degree to push lock fitting if you want to use a 2nd piece of push lock hose to connect filter)
  • Some 1/4″ and 5/16″ hose and possibly a Tee for connecting the vapor line to the Fuel Command Center.
  • Handful of spade and ring wire connectors

If you are mounting to an intake that accepts both spread and square bore manifolds, you may want to purchase an Edelbrock 2732 1/16″ thick adapter plate (or equivalent).

Parts specific to my situation (Trans Am with a 72 intake):

  • Edelbrock 8015 linkage adapter
  • Edelbrock 2696 Square-Bore to Spread-Bore Adapter
  • Mr. Gasket 56C Carburetor Base Gasket (because the spreadbore gasket in the 2696 is junk)
  • Mr Gasket 6399 Air Cleaner Stud with 5/16″ adapter

Conclusion

I’m pretty pleased with the ease of installation and the performance of the FiTech. I now can hand my wife the keys and not worry about the car getting flooded or over cranked because she forgot to push the gas pedal down before cranking. I’m also pleased by the exhaust smell which is much cleaner at idle than it was before. Hopefully the system is as rugged as it is easy to install and will last for years to come.

MSD 6AL2 Programmable Installed – Purrs like a kitten

If you’ve been following project Trans Am, then you may recall that I had to replace the Pertronix Flamethrower distributor because it was acting whacky. I was temporarily running a Cardone distributor with light springs in order to get by for the winter. I maybe drove the car 100 miles with this temporary distributor, but it worked better than the Pertronix at least. Just to recap, the Pertronix for some reason was retarding the timing rather than advancing when rpm’s increased.

When I discovered the MSD 6AL2 Programmable model last year, I was initially going to keep the Pertronix distributor, lock out the advance with some epoxy and replace the module with a 2 wire harness from MSD. Over the winter I found an MSD Pontiac distributor on eBay for a song. Smart move at first, then I discovered that I needed to buy another composite distributor gear because the shaft diameter used by MSD is not the same as the factory. I got a BOP Engineering composite gear for an MSD distributor.

Though they cost twice as much as a bronze gear, the BOP Engineering composite gears are worth every penny. The composite gear I was using on the Pertronix looked brand new when I pulled the distributor out.

Official parts lists:

  • MSD 8563 Pro Billet Distributor
  • MSD 8207 Blaster SS Coil
  • MSD 6530 Programmable 6AL2 Ignition Box
  • MSD 84033 Coil Wire
  • BOP Engineering PDG38 Composite Distributor Gear

I am currently using Pertronix spark plug wires. Someday I will replace them with MSD 31193 Black 8.5mm spark plug wire set.

I ran into one challenge mounting the coil on the firewall. The original plan was to bolt the coil directly to the firewall using the MSD mounting isolators. What I did not anticipate was that there was a gap between the firewall and the cowl, I would not be able to reach into this small gap and tighten the provided fasteners. I ended up fabricating a plate to mount the isolators to, then fastened the plate to the firewall using sheet metal screws. It came out ok, but if I did it again, I would mount the coil 90 degrees from how you see it now to prevent sagging on the 1 isolator side of the coil (see photos below).

I programmed the 6AL2 knowing that the timing curve is actually retarded, not advanced. What I mean is, the MSD software lets you set the all-in timing, then you can map your curve from that timing in retard degrees. I set my initial timing between zero and 600 rpm to 20 degrees retard in the software (to be at 16 degrees). I set the 650-1,200 rpm to a 14 degrees retard (to be at 22 degrees at idle).  I then charted my all-in point at 2,700 rpm to a 2 degree retard (to be at 34 degrees all-in). This makes the timing curve between 22 degrees and 34 degrees between the 1,200rpm and 2,700 rpm range. I set the timing to 22 degrees with the timing light at idle (if you are following, this is 14 degrees retarded from all-in point in the software). I decided on this initial curve for a couple of reasons; If I want to add 1-2 more degrees of all-in timing, I can without touching the distributor (you cannot advance timing beyond zero retard with the MSD software). I set the zero to 650 rpm to 16 degrees so cranking rpm timing is optimal (no more hard starting).

The MSD 6AL2 Programmable Results Are Amazing!

Since the upgrade, my engine now purrs extremely smooth at idle. When I hit the throttle then let off, the rpm’s quickly come back down. The engine also seems to burn the fuel better. There is definitely a noticeable difference between an HEI and the MSD system.

If you are chasing a special timing curve that you cannot reproduce with weights and springs, I totally recommend the 6AL2 programmable. If you like controlling parts of your car with your computer (like me), then this is also perfect for you. I’ll never mess with a mechanical advance distributor again.

MSD 6AL2 ProgrammableMSD 6AL2 ProgrammableMSD 6AL2 Programmable

Project Trans Am May – July 2015

This early summer I got a few things tidied up with the Trans Am.

Gauge cluster repaired, replaced headlight switch, back to white lights

Three things that have been driving me crazy, that my factory tachometer doesn’t work, the odometer portion of my speedometer was not recording anything, and the red LED lighting is not as bright as I hoped.

I tested white LEDs in a spare cluster I had in the house and found the white LEDs reflected better off of the factory light blue than the red LEDs were reflecting off the red reflective paint I used in my cluster. I then proceeded to take apart my cluster and painted the inside with a gloss white paint.

While I had the cluster apart I swapped out the speedometer with a 160 mph speedometer from a 1973 Firebird I picked up at a swap meet this March and I swapped out the tachometer from the spare cluster. I then found the clock from the spare cluster was broken, which lead me to take apart the cluster again to delicately swap the clock portion only. Replacing the clock on a 79-81 is not an easy task, you have to remove all of the needles from the clock and the tachometer in order to safely remove the clock. I also painted the inside of the fuel volt meter gauges with the same gloss white.

While I had the dash apart I replaced the headlight switch and replaced the printed circuit behind the cluster with a new one.

The results are fantastic, the tachometer matched the reading from my 2″ AutoMeter tach.

The speedometer is now recording miles as well and the speedometer needle is very accurate and no longer twitchy. While I took the old speedometer out, I discovered the gear that runs the odometer was broken, which explains why the odometer was not recording.

Gauge Cluster Gauge Cluster Gauge Cluster

Exhaust system tweaks

Since I got the Pypes system installed, one of the most annoying problems with the exhaust has been the drone noise in the car caused by the X pipe. This drone was not there when I had their X pipe system paired to factory log manifolds with a mildly built engine. Last spring I had the motor gone over by Don from DCI Motorsports. He converted the motor to a roller cam, increased compression by shaving more off of my heads and also ported the heads. With the upgrade I decided to switch to Factory Ram Air 3 style exhaust manifolds, they are comparable to shorty headers except they are cast iron. Though These modifications I am sure caused the droning sound, it was unbearable.

I also had some clearance issues with the pipes over the axles, no matter how I lined them up they were hitting the bottom of the car.

One other issue was with the down pipes. I had put them on the wrong sides. I was unaware at the time that the shift linkage needed the pipes to toe-in (for lack of a better description). I’ve seen pictures of folks installing the downpipes both ways, so I assumed it did not matter, until it came time to button up the linkage with my steering column.

In May I finally had all these issues fixed at a local muffler shop. While they had the down pipes off the car, I also had them add Oxygen sensor bongs. They did a decent job. One of the down pipes is a little lower than I would have linked, but otherwise the system is no longer hitting against the bottom of the car around the axle, and I was able to utilize the bongs this August!

 

Speedometer cable swap to non-cruise cable

I decided I will no longer worry about hooking up the factory cruise control. I was looking at some aftermarket systems that install much clear in the engine bay as well as not require engine vacuum to work. I removed the transducer

Shift linkage adjusted

With the down pipes now positioned currently, I now have my shift linkage tied to my steering column adjusted correctly. I can now put the car in park without tapping the steering column! 🙂

Coming in August and September

MSD 6AL2 Programmable (purchased over the winter), AEM Air Fuel gauge, and FiTech Go EFI 4 with fuel command center.

Project Trans Am – June through October (Summer Update)

From June up through October, I’ve been working on the Trans Am off and on with a couple roller coaster problems. First, some pictures now she’s driving under her own power!

Trans Am On the Road Trans Am On the Road Trans Am On the Road Trans Am On the Road

Now lets re-hash the summer…

Upper Radiator Hose and Radiator

When I first got the motor in the car and I was taking the car on small trips to break in the rings and get things done like the wheel alignment, I randomly had a problem with the upper radiator hose blowing off the top radiator inlet. After the 2nd time it happened, I went to Google to see what could be the problem. It sent me down a goose chase, I started thinking that there could be issues with the water pump, or with the coolant mixture, you name it all the bad things that it could be came up on Google. Luckily I didn’t let that get to me, because nothing on the web actually explained the problem.

One fact, the radiator hose would only blow off 5-10 minutes after driving the car. It would never blow off while running. Also important to note that the coolant circulates into the radiator from the engine through the top radiator hose. the thermostat would have been closed when the coolant was very hot, allowing pressure to build once the engine was off between the radiator and the top radiator hose. With this knowledge, you would assume the radiator pressure would be alleviated in the overflow tank. So logically I replaced the radiator cap first. That didn’t fix the problem, but it did lead me to check the top radiator hose was the right hose.

When I first got the car back in 2009, the first things I purchased were new radiator hoses filters, etc… I knew looking at the car that anything of rubber in the car needed replaced. Well somewhere between that time and now, it never dawned on me that the hoses would be slightly different between a Pontiac Turbo 301 and a Pontiac 400, and for the radiator they are intended for. And all this research explained a lot when I took the car apart back in 2010.

It appears my 1981 Turbo Trans Am originally came with a 4 row radiator, replacement part number 477 if you are looking at a parts store. I didn’t buy this radiator back in 2010, I got the 3 core 573  radiator. I did not plan on putting air conditioning in the car so it made sense to save a little coin at the time and get the 3 core. When I took the core support off, I noticed the current radiator was loose, the rubber mounts were deeper than the radiator by about 1/2″. I ended up ordering new mounts that fit the 3 core radiator and thought nothing of it. Now I know, those mounts were for the original radiator, which someone more than likely had to replace in the lifetime of the car and they replaced it with a 3 core but used 4 core mounts.

After all that, I decided lets try a cut to length pre 1979 radiator hose. While I was at it, I pulled the thermostat and drilled a 1/8″ hole to allow some coolant to pass through the radiator to prevent vapor lock, but also to allow (in theory) some of the pressure to go back into the motor. The new cut to length hose failed too. By this point I’m getting very frustrated with this hose blowing business.

So here’s what really caused my problems. The radiator! The 3 core 573  radiator upper inlet has both a 1.5″ and then a stepped down 1.25″ neck. When I used the radiator hose for the 301, it fit perfectly using the 1.5″ second step, but it did not allow enough of the hose to slip over, causing the clamp to clamp around the lip , rather than before the lip. This was the problem! Basically when the engine was off, pressure would build at the top hose, and the clamp wouldn’t hold the rubber because the clamp was not behind the lip of the radiator inlet. I added a new clamp at the 1.25″ step of the radiator inlet and I haven’t had the hose blow off since. More than likely the 301 turbo hose would have worked just as well, the thermostat didn’t need the drill hole, and the other radiator cap was more than likely fine too. Live and learn!

Radiator 2 step inlet 301 Turbo vs Pontiac cut to length upper hoses

Also note, the 301 / 301 Turbo radiator hose would need trimmed about 2″ at the radiator side leaving a hose with the diameter of 1.25 which would fit the radiator’s 1.25″ 2nd step inlet perfectly. The cut to length Pontiac hose I believe is for multiple model cars. I would say that if your putting a Pontiac 400 into a 301 car you can use the 301 hose just keep in mind the diameter is not 1.5″ throughout the hose like the cur to length hose. If I were to run a 4 core radiator, I would definitely not use the 301/301 Turbo hose.

New 17″ Year One Wheels and Nitto NT 555 tires

I decided to go with Nitto 555 tires with the 17″ Year One wheels. Once I picked my tires size 255/50R17 , I really only had a handful of brands to pick from. The Nitto NT 555 was the best priced and well reviewed performance tire. If I had the cash, I would have considered the BG Goodrich g-Force T/A’s, but they were just out of my price range. I also considered Kumho Ecsta ASX (and the summer tire SPT version) but ultimately decided that I wanted the performance tire to have better wet traction, which lead me to go with the Nitto NT 555’s.

The results are in, these wheels and tires definitely improved the handling of the car. Actually, they amplified an issue with my steering box, which is the next item on this posts list. It is definitely worth the investment. No one makes performance 15″ tires, and even if they did, they will never perform as well as a lower profile tire.

Burnouts are harder to do with these tires,  the wider profile tires definitely want to grip, which is a good thing. I get an initial rip of the tires, but then they start crawling the car forward, where the older tires, particularly in a turn, could keep letting loose with no traction.

New Year One Wheels and Nitto 555 Tires compared to factory snowflakes New Year One Wheels and Nitto 555 Tires compared to factory snowflakes New Year One Wheels and Nitto 555 Tires New Year One Wheels and Nitto 555 Tires

I am keeping the old wheels and tires until I get the car painted.

Lares remanufactured steering Box rebuilt by Steer and Gear in Columbus

In 2012 I bought all new suspension components, at the time I also ordered a Lares (brand) remanufactured steering box from RockAuto. I didn’t think about bench testing it, I just assumed it was assembled correctly and put to factory specs. When I finally got the Trans Am on the road this summer, I noticed a lot of slop. At one point I thought perhaps it was my aftermarket intermediate shaft (more on that next) because it did make a bit of noise at the u-joint to the steering column. But once I got that off and put some vice grips on the gear side of the steering shaft, I really noticed the slop in the steering box. It was worse than the steering box I was replacing, which had 156k miles. I think I spent about $80 on this re-man steering box, it was definitely over 2 years ago with no warranty at this point. So I did a little research to see what I could do to the box and found out how to adjust the gear box on a bench using a very low inch pounds torque wrench. $40 torque wrench later (I had to buy a Park brand torque wrench for bicycles, only quality company to sell a torque wrench in the inch pounds needed for this), there was still way too much slop in the box. At this point, I decided to take it to a re-builder to see what was wrong, and I am so glad I did. I took it over to Steer and Gear in Columbus, they are known for rebuilding Mopar steering boxes. They only had it for 2 days and it came back brand new! Apparently something was not seated correctly during reassembly which caused everything else inside the box to not line up properly, causing a “smorgasbord” of issues with the box. All Steer and Gear had to do was reassemble it correctly.

When I got it back, it was super stiff, just a slight touch of movement on the steering shaft side showed pitman arm movement. You can’t get any better than that! Driving the car went from being a wobbly mess to a one-hand enjoyment!

Steering Box

Steer and Gear did paint the box black, but decided to re-paint it with Dupli-Color Cast Iron gray so it matched my other steering components.

Intermediate Steering Shaft

in 2012 I bought a reproduction intermediate steering shaft, mainly because it has a new rag joint. It installed fine, maybe too easily. I did not think anything of it until I started driving the car. My buddy Joel noticed that when I would turn left or right, there was a clunk sound in the steering column. While I was fixing my steering box issues, I noticed that the intermediate shaft at the steering column side was producing the noise. After investigating, I found that the D shape coupling was not a tight fit and there was just a hair of space where the coupling could wobble. Though it did not appear to effect the steering, it did make noise, so I swapped back the old intermediate shaft and I’m now living with the old rag-joint.

The ultimate fix is to disassemble the coupler end of the new intermediate shaft and put the factory coupler end on it. I will come back to this in a year or two if the steering starts to bother me. As of current though the steering is pretty tight, though I suspect a 156k mile rag joint will not perform as well as a brand new one, it’s not doing too bad either.

Fuel Line from Fuel Pump to Carb Modifications (in progress)

It was brought to my attention that I should upgrade the fuel filter that I’m using between the fuel pump and carb to ensure adequate fuel during heavy acceleration. The solution is to replace the factory filter with an inline Fram G15 filter. I thought I had a good idea of having a factory line cut and barbed 4″ before the carb, but my plan did not quite fit the space provided. My last tests I used rubber hose in a bend. I am still not getting the clearance I wanted. Due to other issues I’m trying to resolve, I decided to go back to the factory hard line and factory filter setup, but I do plan to revisit this in the spring. Here are some pictures so you can see the progress. My goal is to have a setup that looks factory. One thing I hate is when you see hoses thrown into an engine bay.

IMG_20140821_093754 IMG_20140821_094011 IMG_20140822_183043 IMG_20140730_155112

You can see in the last picture that I was overzealous assuming the filter could fit in that last section of the fuel line. It almost worked, but was too tight and not serviceable. I also looked at using regular hose, but it quickly kinked. I then tried using a spring to reenforce the hose, but then it lead to the same problem of being too tight, plus at that point it was starting to not look factory.

Muffler dynamics

Once I got her on the road, I quickly found the mufflers, which sounded great when I first rebuilt the motor, now sounded like a droning nightmare. The Pypes Street Pro mufflers with factory log manifolds sounded awesome, but now I am running ported heads with Ram Air exhaust manifolds, the Pypes Street Pro mufflers had excessive amounts of drone inside the car, and outside of the car I sounded like an obnoxious hot rod.  I decided to replace the Street Pros with Dynomax Super Turbos, which appear to have quieted down the exhaust, but I still have a drone sound at idle inside the car, albeit low. This very drone problem appears to be a problem a lot folks have over at Performance Years forums, and the consensus is that the drone is caused by a combination  of using Ram Air Manifolds with the Pypes X pipe. The fix is to run straight pipes rather than the X. Not an issue I’m now concerned with, I may eventually replace the X pipe with straight pipes in the spring. We’ll see if the drone bothers me over the coming months. At least now I don’t sound obnoxious.

Again though I have to say the Street Pro mufflers with the log manifolds sounded quite nice. I suspect the logs cut down the frequency of the exhaust significantly enough that the Street Pro’s rumble was desirable. Also important to note, Street Pro mufflers are not intended for street use. You want a street Pypes muffler, you need to get the “race pro”. Figure that one out.

Ignition System Blues

The last of my problems was with my Pertronix distributor. Near the end of the summer I had a hard time keeping the motor running. When I checked it with a timing light, I observed erratic timing. At first I wrote it off as this is just how old cars work. But at one point it really got out of hand. The last time I checked it before I took action, I observed the timing retarding when I revved the motor rather than advancing.

I did some research, and I couldn’t find much about the problem, except for a handful of folks who complained about it happening to them with their Pertornix modules, I didn’t have much to go by. I was tempted to order a replacement Pertronix module to see if it fixed the problem, but quickly found that a brand new Cardone OEM replacement distributor is 1/2 the price of a new Pertornix module, plus swapping the entire distributor would be better diagnosing the problem. I did have to order another distributor gear because I have a hydraulic roller cam.

Don at DCI curved my Pertonrix distributor specifically for the cam. I knew my test distributor would never have the right curve, I decided to put an MSD re curve kit in my Cardone replacement to at least get me into the ballpark for testing purposes. The MSD weights and light springs got me pretty close at least.

The Cardone replacement distributor worked!!!

My timing curve is not quite right, I’m idling at 16 degrees, where I need to be about 20-22, but my all-in at 3,000 is at 34 degrees, and she pulls strong on the street. Lesson learned, ignition modules go bad even if you pay 4x more for the distributor, the quality may not be there.

Ignition Future Plans

My plans now are to lockout the mechanical advance in my distributor and replace the Pertronix module with the MSD 6530 Programmable 6AL. This will allow me to set the exact timing curve with my computer. It will also allow me to set a few more things, specifically a rev limit. Plus I will be able to adjust all this with my computer, which is something I will enjoy I am sure.

While the Cardone distributor is in the car, the plan is to modify the Pertronix distributor for the MSD 6530 ignition box.

I purchased a lockout plate assuming it would work with the Pertronix distributor. It fits the factory distributor perfectly, but unfortunately the Pertronix distributor uses different diameter shafts for the distributor weights and center plate, so I cannot use it with the Pertronix distributor. At this point I’m not sure if I will use the Pertronix distributor with the MSD module or not, I got a few months to make that decision, but needless to say I feel like I wasted a lot of money on Pertronix and I don’t plan on buying another Pertronix product for a long time, if ever.

IMG_20141008_110942

What would you do if you were me? Would you modify the Cardone for use with the MSD 6530 by using the plate pictured above, or would you take the Pertronix and lock out the advance by welding the advance in? I like the idea of modifying the Pertronix at this point, I have nothing to loose, plus I can keep the Cardone as a spare.

What’s Next with Project Trans Am

This may be a very cold winter, so I’m keeping my plans inside the car. I have some wiring gremlins to address, specifically with the left turn signal not always signaling when the headlights are on. I also need to swap out the tachometer, replace the headlight switch, get the wipers working, fix the power door locks, and clean up the trunk. Perhaps next year I will get the car painted!

 

 

 

Project Trans Am for May, 2014 – Engine is in!

I did not do much in April with the Trans Am. I did however send out my front and rear bumpers to a buddy to get painted, which leads us into May…

Motor Is In!

I picked up the Motor from DCI Motorsports at the beginning of the month. Don had it on the engine stand so I could see it run when I came to pick it up. They dialed in the distributor and also tweaked a few other things with the motor before sending me off. It really sounds good, I’ll be posting video of the engine running on the stand very soon on www.dcimotorsports.com.

That memorial day weekend my buddy Joel helped me get the engine and transmission installed for one final time. This time around installation went smooth, so smooth Joel was talking on the phone while we lined up the engine on the mounts! All seriousness, it went really smoothly. On Friday we spent about 4 hours putting together the engine brackets, mounts, starter, then bolting the engine and transmission together and lowering it into the car. Then we spent another 2 hours on Friday, plus another 30 minutes the following day to finish up with hoses, wires, belts, and such. By 10:30 AM Saturday morning we fired up the motor, filled up the transmission with fluid, and monitored the engine oil pressure and temperature. Everything was running as planned, and there wasn’t a drop of oil on the ground!

The best part was when we were done, I put the car in drive and drove the car back into the garage. It’s been years since she moved on her own power!

DCI Motor in car DCI Motor in car DCI Motor in car

Bumpers back from Paint

The following week I went to pickup the bumpers. Man they look great! Too good actually, they stand out compared to the rest of the car. But that is ok, I would rather have shiny black bumpers and a dull black car then a dull black car with a maroon front bumper and a gold rear bumper. 🙂 THANK YOU PETE!

Bumpers Painted Bumpers Painted

Bumpers, Fenders and Hood Are Back!

The last weekend of May  I got the bumpers, fenders and hood installed. My dad helped me get the hood on, thanks dad!!! Gaps are not all that great, but for a first time assembly I’m pretty pleased. From what I understand, I may not get them much better than this.

Fenders and Hood on Fenders and Hood on Fenders and Hood on

For now I am running the 81 Turbo blister hood, but later in the summer I will be ordering a new “shaker” hood, like the one you see in the background of the last 2 pictures. The one pictured has 2 holes drilled near the shaker opening and will cost as much to repair as it will be to replace it with a reproduction hood. From what I’ve been told, the reproduction hoods fit well and have a special coating on them which will make it easier when it comes time to paint.

Still Some Wiring Issues

I still have some wiring issues. The turn signals are not working when the lights are on, and the tachometer stopped working during the last engine run. I have my work cut out for me with the electrical for sure!

What’s Next

Drive the car! (Spoiler alert, I’ve already drove the car around the neighborhood to test the transmission and brakes, we’re good to go).  Next is to take the car in to get the front wheels aligned, then get tires for my new Year One snowflake wheels, resolve some wiring issues, then start on my secondary features list (cruise control, power door locks, power trunk release, etc…)

YearOne Cast Snowflake 17×9 Wheels

I got my YearOne Cast Snowflake 17″ wheels this week! They look great!

They package the wheels very well. They ship 2 wheels per box, with packing paper in the top and bottom of each box. Each wheel is packaged in a retail box with special elastic padded rings around each wheel. The front has a combination of Styrofoam and netting to keep debris from getting in. Each wheel is then wrapped by very thin plastic to keep them clean during shipping.

The wheels themselves are light, less than 15 lbs each. Lug nut holes are deep with 60 degree conical seats to accept any kind of lug nut and can fit most GM (and other) vehicles. Factory snowflake lug nuts are a tight fit within the lug nut holes. The depth is so deep the factory snowflake and factory acorn lug nuts look kind of funny recessed (see picture). I’m going to try a 1.45″ deep lug nut next week to see if they look better with these wheels. Other than the lug nut depth being a bit odd, these wheels are awesome!

YearOne Cast Snowflake 17" Wheels YearOne Cast Snowflake 17" Wheels YearOne Cast Snowflake 17" Wheels

 

These are a second generation version of the YearOne Cast Snowflake Wheels. To see the first generation wheel, visit the 78ta.com forums thread post contributed by Aus78Formula: http://www.78ta.com/HTAF/index.php?topic=41799.msg427726#msg427726

The wheel has a 5.125″ (5 1/18″ back spacing (previous generation had 4.875″ backspacing). If you want the original backspacing, all you have to do is buy a 1/4″ wheel spacer. You may find that a 1/8″ or 3/16″ wheel spacer is all you really need.

The hub hat diameter of these wheels 72.6mm (or 72.56mm). Factory hub is 70.3mm, so if you want to be 100% sure your wheels are centered you can get hub centric rings for that.

 

 

 

Firebird 81 to 78 tail light and rear bumper conversion

To convert my 81 Trans Am to a 78, both the front and rear bumpers and lights need to be swapped. The front bumper, headlights and grills are quite easy to swap, simply unbolt the front bumper, brackets and hardware and bolt-on a 77/78 front bumper and hardware. Specifically, the metal bumpers, foam inserts, front urethane bumper cover, headlight and grill header, headlights, grills and brackets. If you have a Trans Am, you will also need a lower center spoiler. Though it sounds complicated, it’s an easy swap.

The rear bumper and taillights on the other hand, is far from an easy swap. There are really 3 basic ways you can do the conversion: swap the tail panels (body work), add new holes to the existing tail panel, or make brackets to adapt the older taillights to the newer tail panel. I opted for the 3rd option this way I was not adding more holes to the body and this allowed me the option to switch back to the 79-81 style bumper if I changed my mind later.

Making brackets for the taillights is only part of the conversion. Let me cover what’s necessary…

1. Gas tank filler neck

The gas tank filler neck on a 79-81 Firebird / Trans Am is longer so it protrudes further out. When you open the taillight center door on a 79-81 the gas filler neck is right there, easy to get to. The 79-81 gas filler door is flush the the taillights. When you convert to a 77/78 (1976 is also the same rear bumper style but not as ideal, will explain that shortly), the gas filler neck is now covered by the license plate door. This door is recessed (not flush) in relation to the taillights. The inner sides of the 77/78 taillight housings hold the bezel for the lights that light up the rear license plate. The depth is enough that you cannot use a 79-81 gas tank. It is possible to get only the filler neck for a 77/78 Firebird and get that swapped by a gas tank repair/radiator shop. In my situation I decided to replace the entire tank with a 78 length filler neck since I suspected my old tank leaked anyway.

2. Rear bumper and license plate gas filler door

The rear bumper may require slight modification in order to fit at the tail panel center portion. I did not have to modify the 78 donor bumper I had, but the fit was very close, maybe 1/16″ gap between the bumper and the tail panel. I read somewhere that someone had to cut 1/16″ off their bumper cover to make it fit at the center portion of the bumper cover, so your mileage may vary.

The license plate gas filler door will be tricky to figure out where to locate. I went by pictures of other cars to locate mine. The 79-81 trunk sheet metal includes a bit of extra metal just above the trunk key hole, mine had a band of rubber that the 79-81 gas filler door used as a stop. This will cause clearance issues, so watch as you mount your rear license plate gas door that it clears this lip. I may grind/cut this lip off once I decide to commit to this swap permanently.

It is possible to use a 76 rear bumper, but I would recommend looking for a 77/78 instead. The 76 rear bumper was a 1-year only design. Rather than use a Styrofoam or plastic grate mesh to fill the gap between the bumper cover and the actual steel bumper, they filled the entire void with polyurethane plastic. These bumpers have a reputation for not keeping their shape due to the extra weight in them.

3. Wiring of the taillights

Depending on the taillight harness your car currently has, you may or may not have to modify your wiring. My car, a 1981 Trans Am, had the rear harness that included 2 harnesses that took style 1157 bulbs and 2 harnesses that took interior style 194 bulbs for the parking and brake lights. The harnesses that take the larger 1157 bulbs will need to be modified slightly in order to get them to plug into the older 77/78 style taillight fixtures. In the process of going through my wiring I ordered a replacement pigtail and found the replacement pigtail fit without modification. I decided to order 5 more and replace all of the pigtails that the harnesses would plug into the taillight fixtures without issues.

Note: I do not know how many variations of taillight harnesses there were between 79-81, but I do know that the Trans Am’s, Formula’s and regular Firebirds had different rear taillights. I believe the Trans Am’s had a smoked look and the parking lights were lit almost all the way across (minus the fuel filler door).

The 79-81 license plate light harness is different than the 78 as well. 79-81 only use one light centered over the plate, where 78 and older use two lights in fixtures on either side of the license plate. Since I was replacing the pigtails for the parking/brake lights I decided to run new pigtails for the 78 style as well. I got all the pigtails from RockAuto, which had the best price on them. Here’s the part numbers:

  • Dorman 85832 (qty 6 for turn signal and parking lights)
  • Dorman 85866 (qty 2 for backup lights)
  • Dorman 85814 (qty 2 for license plate lights)

One other advantage of using the existing 79-81 wiring rather than getting a 78/79 rear harness is with the gas tank fuel gauge wire. By modifying my existing harness I was able to maintain the same connector for the 79-81 gas tank sending unit.

I wrapped all my new wiring in fleece electrical tape then covered everything with new 1/2″ wire loom and purchased new wire loom clips (Dorman 85656) to use the existing 79/81 wire loom mounting locations.

4 Modifying 78 taillight housings to fit the 79-81 tail panel

The taillight housings you decide to use will need to be modified in order to make them fit within the confines of a 79-81 tail panel. More specifically, the passenger right side tail light fixture will need to be modified (as pictured) in order to clear the tail panel. Note that the mounting holes on a 79-81 tail panel are not uniform, the holes are offset differently on the left than the right because the left/drivers side also held the hinge for the taillight gas door.

Once I had the taillights modified enough that I could hold them into position, I proceeded to cut the studs off the aluminum outer housing then drilled and tapped each mounting location with a 1/4-20 tap, approximately 3/4″ deep. I drilled and tapped all of them just in case I decided I needed them for mounting.

I used 3/16″ thick aluminum plate (picked up a bar for $10 at a local hardware store) and cut pieces to fit different areas to relocate mounting holes appropriately. Each taillight mounted to the original tail panel with 8 mounting studs. My new brackets only mount with 3, so it was critical that the three mounting locations I picked were strong. I used 1/4-20 threaded rod cut to specific lengths for the new taillight studs. when I determined where to locate the studs in the aluminum stock, I drilled the holes, test-fit then tapped each hole with a 1/4-20 tap.

Once I had all of the aluminum stock cut, drilled and tapped to my needs, I threaded the 1/4-20 bar stock into the holes ten secured them with nuts to act as a jam nut. I then used 2 additional nuts to locate the final positions against the rear tail panel using the 2nd nut as a jam nut. Washers finish the job, with the plan to add rubber washers between them and the body when done to make a water tight seal.

The remaining holes left uncovered will be plugged with rubber body hole plugs. Ames Performance sells the size I needed, which I believe was 3/8″ (don’t quot me on that diameter). The factory used large holes in the body, it is forgiving for this modification.

Remaining Details

I currently have a buddy painting my 78 bumpers starlight black to match the rest of the car, that way this summer I’m not driving around with a Frankenstein Trans Am.  It is important to note that an 81 to 78 conversion is not 100% complete just by swapping front and rear bumpers alone. To truly convert the car, the following items will also need to be swapped:

  • Outer whale tail (rear spoiler) corners will need to be swapped with 70-78 styles. Take a look at some rear pictures of a 78 and compare with a 79, you will see the 70-78 sweep down into the rear panel to a point, where the 79-81 come down evenly with a square edge. 70-78 (that I have found anyway) are hard plastic, just like the center spoiler section of my 81. The 79-81 corner spoilers are urethane, so if you don’;t know what you have, take them off and look under them. If there is yellow, you have 79-81 rear spoiler corners. I am definitely swapping these, the 79-81 tails just look out of place with this rear bumper (see my pictures below). The will be swapped when I take the car in to get painted in the fall.
  • Lower front and rear side wheel spoilers will need should to be swapped with 70-78 styles. 79-81 rear side spoilers have sharper turns in them, they look slightly more aggressive. The 70-78 style have a more gradual rounded corner to them. Look at pictures to see the difference. I am going to use my 81 wheel flares this summer. If it drives me crazy then I will order a set of Danko brand 70-78 wheel flares before I get the car painted.
    Note: I changed “need” to “should”, mainly because you can use the 79-81 wheel spoilers. Since I put larger wheels with lower profile tires on the car, I’m beginning to prefer the 79-81 spoilers with the wheels. If you decide to go this route, you need to use the lower chin center spoiler from 79-81 with the 79-81 wheel spoilers, as the 77/78 lower chin spoiler is designed to mate up to 70-78 wheel spoilers. Also important to note that the 79-81 lower chin spoiler bolts on along the core support, it may possibly work for all 70-81 cars that use 79-81 wheel spoilers.
  • Rear drum brakes. I am going to keep my rear disc brakes, but technically there were no 70-78 Trans Am’s with rear disc brakes. Purists will just have to deal with it! 🙂

Here are some pictures of the 78 bumper and taillights mounted to my 81:

78 bumper 78 bumper

Here are some close up pictures of the back of my custom made 78 taillights:

Customized 78 taillights Customized 78 taillights Customized 78 taillights