85 S Model
SBF swap
Iron heads
C4 trans
9" rear
Fiberglass hood, fenders and bumpers

How light do you think I could make the car?
-Cris

 

My setup is similar to yours, I weighed my sbf 85 at 2520lbs with a 1/2 tank of gas. Mine may be a bit lighter since I am running a manual trans with a stock mazda rear but could be offset a bit by the fiberglass body parts.

my setup,
93 5.0 carbed with iron gt40-p heads and tfs1 cam
95' mustang gt t-5 trans
GS drum rear with GSL lsd unit
grannies steel drive shaft
No weight reduction efforts at all
no sun roof (mines the only FB I've come across that doesn't have one )

If you want to go lighter you could gut the interior and replace the glass with lexan, but the car would be horrible to drive for any extended period of time.

BTW 1 gal. of gas weighs a little over 6lbs, keeping the car under 1/4 tank would save 75lbs.

 

You haven't said what you are planning to do with this car. If it is a race car with 500 horsepower, then the 9 inch rear end makes sense. But if you are doing that, you definitely should be using aluminum heads.

For street use, the stock rear end from a GSL is certainly good for at least 300 horsepower, and for more power, a Ford 8 inch from a Maverick, for example, is the correct width. Either one is MUCH lighter than the 9 inch. Remember that on a light car with street tires you can only put down so much torque and the wheels will spin, and you won't break a stock rear end unless you drive like a real idiot. I think the main benefit of the 9 inch is to impress your friends, assuming they are drag racers and not engineers.

My 84 GSL had a 302 with about 250 hp to the wheels, stock gsl rear end, aluminum heads, intake, radiator and water pump, a really heavy Ford AOD trans and complete interior with power windows, sunroof, but no AC or Power steer. It weighed 2550 without fuel.

 

Word!
My open diff did just fine despite being the weakest possible option for an 1st gen, I swapped diffs because one tire would break lose when ever I did a pull so in went to a GSL unit. Right after I bought first rx7 years back (a bone stock 12a gsl) I changed the rear diff oil and had a bunch of gear teeth stuck to the magnetic plug, it's all in how you drive it. Not to bash Crispin38's choice in rear ends, it is nice to know your rear diff is ready for any future mods but a gsl rear is great for a street car.

 

how light can this car get to once its been gutted and body panels replaced with carbon fiber?

 

Under 2200lbs if done right. Mine was alsmot 2400 even with an iron headed SBC and th350 trans. (9" rear)

Also for what it's worth you don't need a 9" rear end unless your planning well into the 700hp+ range and using a trans brake IMO. I used the auto LSD in my rx7 for over 5 years (no trans brake) at 500hp levels. I swapped in a ford 8.8 after that. The 9" is a huge heavy thing. I wouldn't put it anywhere near a street car.

 

Nice

 

I must be a real idiot lol i blew up 2 gsl se rear diffs before deciding to get a granny's 8.8 almost 10 years ago . They may hold up with street tires and a auto but not a stick with slicks or drag radials . Sent the carrier out the back both times and the first time didn't even get a reaction time ;/.

 

Mine weighs 2650 with half a tank

 

If I could get mine under 2200#'s I would be thrilled ! Anyone actually get one this light ?

 

Depends how you launch it. Dumping a clutch at 8k with slicks out back will break alot of parts. Preloading the suspension and properly slipping the clutch will result in a much longer life span. I launched my AWD talon at 8k and never had a problem. The rearends have alot less meat than the GSLSE rearends.




Sure with a rotary. Strip all the usual parts. Then remove all windows, cut up the doors remove bumpers you should be in the ballpark. Having it be a realistic v8 powered "street car" and weighing 2200lbs won't happen IMO.

 

Your right , my car apparently lifted the wheels with a nothing small block chevy with a auto on nitrous before i owned It . That being said i was leaving the line at maybe 3000rpm first time with slicks next time with m/t drag radials . I think it was bs It had the wheels up and i know of a couple others first gens with 302s with autos and they blew up . So out of experience and seeing lower powered engines than mine take them out . I can honestly say there weak . Both of mine blew the caps off and had to weld up the back of diff . Im not sure about the others . Maybe with small tires or real street tires but not with traction .

 

Is all that jibberish even a complete thought?

I've seen lots of OEM rears break with an NA 13b. It's the shock to the drivetrain that kills them.

All I'm saying is if you know how to launch a manual properly, you don't shock the driveline. The same rearend that blew up with 100ftlb may take 450ftlb plus. The turbo 302 GSLSE I helped build made over 600hp and the rear end lasted a good 2 seasons at the drag strip of 1.5x 60 foots and a ton of street miles before it was replaced with an 8.8.

My turbo 3.8 build went low 1.5x's for 6+ years on the "wimpy" FC automatic diff. I pulled it for an 8.8 as well, but it never failed.

 

Have you even driven a stick or drag raced one ? There is always shock ! Unless you shift like a granny . Oh but then maybe the gsl se diff will last . 1.5 sixty foot is awesome its a dream for me right now . If i could get a 1.6 would be in heaven . Maybe next year

 

I didn't mean to offend if i did i just know what you mean by shocking the tires i wasn't side stepping the clutch is all i meant but releasing it aggressively at 3000. I was trying to bust the 11s and a 12.02 1.87 sixty foot is the best i could muster rolling out from 2500 with street tires . Pretty sad .

 

Clutch manipulation is the trick. Id love to do a hard launch but my wallet tells me to be patient

 

No offense taken. Yes, I've raced quite A few manuals. I load up the suspension first with the hand brake. Set my 2 step at 7200 and ride the hell out of my feramic cutch. Little different with a v8, but you should launch at Higher rpm imho. My v8 was set at 4800.

This is a 1.6x 60 on my daily. Runs high 10s @ 124. Its a manual.


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