1994 FD With LS3 427 SS Build

[stlide]

Here is my build thread for my 1994 FD RX-7. The intent of the project is to build a dual purpose track/street car. I picked the FD for the obvious reasons of good looks, light weight, good suspension kinematics, many damper options, and easy to swap in an LSX. I cannot think of a better engine/chassis combination available. I plan on doing drag racing and autocross, but the build is being geared toward road racing. This car will be driven on the street. I want to be comfortable while driving allowing me to take the car on long trips. The car is going to do the Hot Rod Power Tour this year and I would like to have it where I want to do many events along those same lines. Below is a summary of what my final setup will be moving toward as this build continues:

1994 FD RX-7
Mast Motorsports LS3 427 SS (eventually I will have an L92 427 with Variable Valve Timing (VVT))
700HP spec. T-56
Kaaz Diff. with 300M Axles
Eibach Springs
Tokico Dampers
Mast Motorsports Fuel System w/67GPH in-tank Pump
JTR 1-7/8 Longtubes
Manual Steering
Air Conditioning
Welded in NHRA and SCCA spec. Roll Bar w/Removable Swing Out Door Bars
Carbon Front Clip (and hood)
Carbon Hatch with Lexan
BBS RK Wheels
PCS D200 Datalogger (To log engine data over the M-90’s CAN Bus and Suspension Data over the analog and digital channels)

This parts on the list are already on the car unless listed below:

VVT
Air Conditioning
Welded in NHRA and SCCA spec. Roll Bar w/Removable Swing Out Door Bars
PCS D200 Datalogger (To log engine data over the M-90’s CAN Bus and Suspension Data over the analog and digital channels)

As I began this build and got up close and personal with the car, I was pleasantly surprised with how the chassis was laid out. It is as close to a race car as any road car that I have seen. It’s the little things that make this chassis easier than most to prepare/maintain. By this I am speaking of the easily adjustable suspension, easy access to fuel sending assembly; etc. I am shooting for mid 2600s/low 2700s without the cage and around 2750 with the cage. Maybe you guys with some weight reduction experience on these cars can tell me if my expectations are in the ballpark. The car sitting on dollies in the pic below weighs 1901 Lbs. (including dollies)

Before I get into the build I would like to get one thing out of the way. Thanks to all who add to this forum. Having the information from this site greatly reduced build time and made for better planning of the project.

Here is the car with paint and fenders installed and no hatch. This is what we have to work with. Sorry in advance for the sub-par photography.

I typically don’t like carbon left unpainted unless it is on a race car, however, I was really pleased with how the look turned out. The hood is not carbon yet, but will be eventually.


Shaun
1994 FD RX7
Mast Motorsports LS3 427 SS
VVT in the works

[aleXander]

I love the way carbon looks. You should do the whole car in it and be the lights FD in the world! Good luck with the rest of the build.

[LS1-FD]

Your car is looking very good. You might want to think about the cobra diff swap. I have owned 2 427 rx7's and I can tell you that the cobra diff helps out alot with traction.

Mike

[burtoncr]

Is that chassis from Houston? I remember something like it being for sale a while ago.

[Pete.McP]

The car looks good. Can't wait to see more progress. FYI, I dont' think SCCA allows removable door bars.

[Sabre002]

wow we have quite a few race car builds going on here.

[stlide]

Originally Posted by burtoncr

Is that chassis from Houston? I remember something like it being for sale a while ago.

Chassis is not from Houston, but I am originally.

Shaun
1994 FD RX-7
Mast Motorsports LS3 427 SS
VVT in the works

[stlide]

I bought the axles from The Driveshaft Shop. I do have to say that my dealings with them both at work and on my own have been great thus far. While building the axles I was a little concerned with the fitment of the tripod joint onto the axle splines. After exhausting the search engine on this site, I called The Driveshaft Shop and they explained the fit. I followed their procedure and the tripods went on snugly. The 300M axles are approximately the same diameter as the stock axles, but they eliminate the stress risers of the snap ring grooves and are of course 300M. I went ahead and taped the axles up to try and avoid extra stress risers from rock dings.

Here is pic of the 300M Axles completed.

I was on the fence about what to do with the diff. For a while I was going to do a Cobra diff. and fab a cradle due to the weight of the stock Mazda piece. I wound up using a Kaaz unit in the stock diff. casing. I was skeptical whether I would be able to use the stock shims on the Kaaz unit, but when I measured the diff. was on the money with the Mazda specs. This was the simplest carrier install I’ve ever done. Below are some pics of the diff. building process.

During the build process.

Kaaz unit installed.

Ready to be cleaned and go back in.

The diff. bushings are a two piece bushing out of Nylon. They are basically a top hat bushing. I don’t know what the popular kits do, but I opted to do mine like this as they will locate the diff. this way. The bushings have a 4340 sleeve that the bolt rides on. Sorry no pics of those.

I set the bias up to 33% and it turns out that the diff. still pops a little on low speed corners. There was also evidence on the shop floor that the inside tire was scrubbing. We’ll see how this setup works out…I may wind up doing a Cobra or Explorer unit in the end. Does anyone know a weight difference between the stock Mazda and 8.8 diffs.?

Shaun
1994 FD RX-7
Mast Motorsports LS3 427 SS
VVT in the works

[gnx7]

You should look up the instructions on how to adjust the Kazz. That is acting like a full locker and will drive you nuts! It will also greatly increase tire wear....

[assault_7]

if you dont mind me asking, why did you opt for an LS3 versus a built Ls2?