Day Dreaming : Grassroots Supercar

I want to throw out an idea to generate some idea discussions. And, I'm hoping to pick the brains of those who make it to the Challenge when we all get there.

Thoughts - I have a 1969 Amante GT Fiberfab body sitting on a VW Chassis. I want to build a low buck supercar-esce vehicle. I have plenty of SBC stuff including a super-cheap pair of turbos (301EE80).

Questions

1. What are some of the low buck rear engine trannies that I could use that are manual and strong enough to handle 600+ HP? (Gearing must allow for high speed at 7500 rpm's)

2. What front end could I use for a high speed car and excellent handling?

3. What rear suspension could I use?

BUDGET is the key component of this dream scheme.

T5 bolted up with the output facing toward the front of the car. Add a 2-gear reversing box (homemade, could use junk transmission guts and steel plate) with the output facing the rear, under the transmission. Run driveshaft from reversing box to your choice of high-horsepower junkyard IRS (Jag, BMW V8/V12, etc.) situated under the transmission or engine. Custom gearshift linkage to reverse the T5 pattern.

You other high-dollar choices are a Porsche 911 'box, a rigged up Porsche 951 'box, a built VW 'box, and probably some other high-dollar setups.

P.S. did I mention that the packaging would be... um, interesting? The rear of that car will need to be jacked way up due to the extra height gained by stacking an IRS under a engine or transmission.

Andrew,

What does Factory Five use in their supercar?

A C4 Corvette front suspension will help.

wheels777 wrote: 1. What are some of the low buck rear engine trannies that I could use that are manual and strong enough to handle 600+ HP? (Gearing must allow for high speed at 7500 rpm's) 2. What front end could I use for a high speed car and excellent handling? 3. What rear suspension could I use? BUDGET is the key component of this dream scheme.

1. None. I've often thought of doing as Winston suggests with the front of a AWD blazer (halfshafts run through the oil pan) and run the front diff flipped to deal with the height issues. And while I was at it use a matched ratio diff for what used to be the rear output of the transfer case to run the front as well. Bingo bango, AWD supercar.

2. Off the shelf probably C4, or C5 corvette is your best bet.

3. This will depend on what trans you use. Again, C5 corvette would be a good start.

I know on the Locost forum there is a guy running a C5 corvette auto trans with an engine directly attached (no torque tube). This seems to only work directly with the auto, as the shifter shaft is in the way on the Vette specific transaxle. I'm sure you could get around this with a trashed t56 case and the vette internals/diff mount. The only problem here is it goes Engine, Trans, Diff, Not Engine, Diff, Trans like the Porsche stuff. If you can tollerate the length (I guess the locost guy has like a 120" WB) this isn't a bad option. If you can tollerate ~300-400 hp max, The Audi S4 6-speed trans can apparently be ran with no rear output and still tolerate the torque. Apparently the Subaru STI/WRX trans is the same way. FWD Passat trans are about a 250-300hp option, and probably the cheapest of the lot. Don't go Drag racing with them though...

Audi 016 2wd transaxle and an adapter for the SBC. the Ford GT40 replica guys love em and they are the same units used in the 944 and 944 turbos. Read up a little more at Porschehybrids.com, etc.

There was also a thread on a Lotus Esprit that used an Audi V8 and 6-speed box in place of the turbo 4-cylinder.

Add an external oil pump for the transaxle to provide better lubrication and perhaps add a cooler and it might help.

BTW, there used to be a VW bug replacement chassis that used fully independent front and rear suspension made by MetalCraft. It is similar to the one from SpecialtyAuto

http://www.specialtyauto.com/Suspension%20and%20Braking.htm

Then there is Rorty Designs

http://www.rorty-design.com/content/CAD_plans.htm

For example:

http://www.germanlook.com/Forums/showthread.php?t=6197&highlight=audi+v8

Miata? I imagine you box in the front suspension from one & make it work, possibly with some widening/narrowing depending on the width of your kit.

John Brown wrote: Andrew, What does Factory Five use in their supercar? A C4 Corvette front suspension will help.

Porsche transaxle flipped upside down

Per the Factory Five website - "Porsche Transaxle Parts from 1990-1998 2-wheel drive 911 models

Porsche G50 or G50 variant transmission"

I looked at Fiberfab, they have a similar car available now. GT-40 wannabe, here's what they suggest:

http://www.fiberfab.us/transaxles.html

wheels777 wrote: 1. What are some of the low buck rear engine trannies that I could use that are manual and strong enough to handle 600+ HP? (Gearing must allow for high speed at 7500 rpm's) BUDGET is the key component of this dream scheme.

There is no such thing as a "low buck" rear engine trans that will hold up to 600+ hp. Then again, in supercar terms "low buck" means different things. As mentioned, a Porsche G50 is your best bet, but they're not necessarily "low buck" in terms of GRM $200X type of low buck. The transmissions others are mentioning out of AWD/FWD applications won't hold 600+ hp (at least, not for long).

Bryce

For front and rear suspension stuff, I'd look at either C4 'Vette or 3rd gen RX7 stuff. The 'Vette stuff will probably be cheaper. You'd need to fab your own subframes and I think you probably know a pretty good fabrication guy.

Again, I'd look at the C5-up 'Vette tranny. No, it won't be the most 'budget' thing out there but I would think it would be pretty much guaranteed to take anything you could throw at it. Again, the fab guy you know should be able to work out the shift mechanism.

A long shot for a reversing box like the homemade version mentioned above: a V-drive boat gearbox might be worth looking at. Like this:

I just remembered, it's a bit of a long shot to hold 600 hp, but I'm guessing it'd get close with typical GM automagic upgrades - TH425. It's a big, heavy pig and it's an auto, but I guess it will take the abuse of 10s in a Fiero without much trouble. They're normally used as a front engine FWD setup, but you can replace the chain with a pair of gears to reverse it and do a rear engine setup. Here's some info on the Fiero swap I referenced to get you started if a heavy auto is worth considering:

http://www.fiero.nl/forum/Archives/Archive-000002/HTML/20041015-1-030268-5.html

http://www.fiero.nl/forum/Archives/Archive-000002/HTML/20031110-1-031409.html

One nice benefit to that trans is that it's in the family, so you shouldn't need any custom bellhousing adapter, flexplate, etc. Not that those things are a huge deal, but it's a nice perk. Also, for you guys recommending using a C5 trans, I'm guessing you've never seen a V8 mated to a C5 trans and diff, it's REALLY long.

Bryce

The C5 setup will be perfect for the kit car (AMX/III) I'm planning on eventually building. The original drivetrain was the same length!

How about this: SBC bolted to C5 gearbox (or even a T56 etc), V drive box on the back of the gearbox but tilted to one side, CV shaft forward to a 4WD front axle (drastically narrowed!) which would fit under the rear of the engine (use a front sump pan) with the diff offset to one side? That would keep the overall length short enough and put the motor over the rear axle for good weight distribution but still narrow enough to go in the chassis. I would think it would be a damn sight cheaper than a G50 Porsche box, too.

The V drive would cause the output to turn backwards but the 4WD front axle would correct that.

It's not unprecedented; the Olds Toronado transaxle used a similar setup all in one housing, but it's a slushbox.

For that matter, why not build a V drive type box which would put the tranny alongside the motor, the way this Toronado transaxle does? Get the guts from a 4WD transfer case to make a chain drive setup, maybe even use the whole thing case and all to put the tranny alongside the motor.

I can't believe you guys.

How bout an STI Subie set up?

It's not 600 hp but you can easily get 400+ and still be street reliable.

He's a bit of a SBC wizard.

I thought of the Miata and C-4 front ends.

As for the trans, I guess I can't help but to wonder what some of these 1200 HP FWD racers are using. It is amazing to see the variety of FWD with 8 second capabilities.

I know I can't be the only one to dream/think about a mid-ship engine mounting. A transverse mount would probably be an easier package.

Oh, here's another front end idea I just remembered: Someone is making a kit that bolts onto a stock Beetle pan(where the beam attaches)that is a complete double-wishbone setup with subframe/springs/steering/etc. all worked out. I wouldn't call it "cheap", but for a Supercar I'd call it "budget"...IIRC, it was priced around $3k.

Or you could always use it as inspiration to fab your own.

wheels777 wrote: As for the trans, I guess I can't help but to wonder what some of these 1200 HP FWD racers are using. It is amazing to see the variety of FWD with 8 second capabilities.

They're running expensive gearboxes with lots of fancy doodads on the insides, many of them starting as automatics. You said budget and manual, remember.

How about you lay some guidelines/ground rules. Does it absolutely have to be manual, or does an auto with manual valve body work just as well? Also, what is "low buck" or "budget" for a grassroots supercar trans. Available at your local U-Pull? Under a grand used? Under three grand with a used trans and mods to hold the power?

Bryce

All right, Wheels. Your first post you said rear engine, your second one you said mid-engine. Which is it?

I'm assuming mid. I don't think you'd be a happy camper with a motor mounted sideways!

I've got a complete IRS from hub to hub including the diff from a Supra that I know would handle 300- 400 hp. You'd have to do your own homework to see if you could build it farther.

The Pantera used a ZF 5 speed tranny coupled to a 351 Cleveland in the mid-ship RWD configuration. They only had 330 hp (though they did 0-60 in 5.5 seconds). I think one of those trannies is worth well over $3000.

What makes a supercar? Do you really need 600 ponies? How big is your budget?

SVreX wrote: All right, Wheels. Your first post you said rear engine, your second one you said mid-engine. Which is it? I'm assuming mid. I don't think you'd be a happy camper with a motor mounted sideways! .... What makes a supercar? Do you really need 600 ponies? How big is your budget?

OK...OK...OK... I mean the engine behind the driver and not behind the rear axle. OK...Paul...I want the engine 7 3/8" behind the driver...no sorry, the front on the block 7 3/8" behind the back of my fat head

I can't afford a super car. I want a cheap lookalike from a $100 fiberglass piece that I own. I won't define the budget until I know the available options for trannies. The 600 HP SBC thought comes from the cheap pieces I own. However, I would consider other engines. And, transverse may be the best option. I am hoping to hear about the different possibilities that others have explored.

I thought that bringing it up before the Challenge would be a good way to start the conversations, in hopes that someone has pictures they could bring down to the event to discuss in the parking lot. I have learned more things in the social hours of the Challenge than I can quantify.

Ah, transverse and no SBC... NOW you're talkin'! Your options just widened dramatically.

An easy and compact one would be a VW VR6.

Then there's the various Mopars, Mitsubishis etc with turbos, and I learned the other day that all the GM front drive engines share a common tranny bolt pattern. So maybe a SC 3800 would fill the bill.

The new impalas have an LS motor that sits the wrong way. When one appears at my junkyard I hope to squeeze it into the Cadavalier.

Big boost Northstar hooked to a TH125/Getrag 5spd

Carroll uses them for big power, a proper reseal, a pair of TD03s, a pair of Audi A6 intercoolers and an Audi inlet Y pipe and you should be good for 475 honest horsepower and you would not need any mufflers, more with more boost.