Mid engine homebuilt supercar (Gruppe B meets Group 5 meets Grassroots)

You could always go the Subaru transmission route and just block off the rear of the transmission.

Or the Lamborghini/Buggati-style route, and mate your engine to a traditional front engine/RWD transmission and 4WD/AWD transfer case, rotate them 180 degrees so that the engine in sitting in the middle. After that, you just have to deal with the reverse rotating output shafts (something I haven't thought 100% through yet). The guy in the picture below did it and made a pretty formidable rally/hillclimb car...

I've put both of these on the table for my Fiero build. The second one would allow for AWD, which could be pretty awesome.

So we’re building a modern version of a Cam Am car that Bruce McLaren or Dick Chapparal would be proud of.....  make two because I want one.  Please use the 5.2 out of a current GT350 for mine.

Also read every Carrol Smith book pronto.

I eagerly await the epic photos.

I've been following videos on Youtube from a South African company called https://v8stealthbeetle.com  It's a guy who used to build GT40 replicas, he's now building a monocoque mid engine chassis that goes under a classic VW Beetle body.  He uses an Audi transaxle and V8 engine; from what I understand the Audi transaxle is pretty sturdy, and it appears to be relatively short since it fits nicely in the Beetle.  

Just one other possibility to consider.

I don’t have much to add except that I suspect we are roughly age/interest peers as I love Lancia 037’s, I love Group B rally, I love Group 5 racers, I love buggies and truggies, I love scratch-built vehicles, and I very much look forward to following this one!!

In reply to WillHoonForFood :

I'm glad you brought up the Lamborghini/Bugatti arrangement! That is another alternative that is doable using factory GM parts. 

This is a C5 T56 transmission: (not transaxle because the diff is removed)

This is a C6 T6060 transmission: (not transaxle because the diff is removed)

This is a comparison of the C5 vs. C6 tailshaft housings:

This is what a Vette T56/T6060 looks like from the bellhousing end:

THIS is the factory piece that makes a reverse mid engine drivetrain possible using all GM parts:
This is the Magna MP3713G transfer case. It is only found in the CT6 AWD models.

What makes this unique is it is a two-gear transfer case...not 3 gear or chain drive like 4x4 transfer cases. 

The 2 gear transfer case reverses the rotation of the output...meaning you can use standard rear axles and driveshafts to receive the power.

According to this page, the differential is 100% variable front to rear. Integrating it might be tricky, but I'm sure the GM techies could figure out how to implement.

https://gm.oemdtc.com/6623/16-na-112-2016-cadillac-ct6-new-model-features

Other reverse mid engine alternative drivetrains:

Fortin 

https://youtu.be/1kR3x7s8pYE?t=100

Weismann

Milner

Of course, those are all deep-pocket pieces. The Milner box is the most affordable of all the options.

You could always homebrew your own transfer case, like THIS mad man:

Those are allegedly gears from a big rig, so that's something to chew on. Being a machinist, that set up would be a walk in the park aside from sourcing gears (unless you brew your own there as well!)
 

As an FYI, this example is already mid engine using an Audi transmission, but the concept could be applied to the Lambo/Bugatti set-up.

In reply to stuart in mn :

That channel is in my YouTube subscription. I've watched every episode. I love what they've done. Just never been a big fan of Beetles.

In reply to ae86andkp61 :

Yeah, I'd say we're sympatico. Thanks for joining us!

In reply to WillHoonForFood :

Those are awesome. That first transfer case looks like bull gears for an Eaton PTO, but I'm not super familiar with those.

That second one looks like a RallyRaid or euro Rallycross build. Those things are wicked! I'd much rather race those than dirt track cars.

In reply to Gingerbeardman :

It's actually from the same vehicle. The guy is apparently one hell of a fabricator and dominates hillclimb. I discovered his work through another GRM member who bought his old car.

In reply to WillHoonForFood :

That's awesome. Got any links?

BeeTeeDubs...love your screen name. Too bad I live in BFE, I can't get away with any shenanigans in town. Fortunately for me, I have 1000's of miles of BLM, Forest Service and county roads to hoon on. Probably why I'm drawn to rally, rally raid, dirt track, 4x4 and sandrails so much.

In reply to AnthonyGS :

I totally would build a CanAm recreation or CanAm V2.019, but I'm literally 8 hours from the nearest track and Bandimere just ain't worth that kinda drive. Besides, I figure a car built using race car parts, driven on the streets, state highways, county roads, BLM fire breaks, Forest Service roads, and ancient 2-tracks should probably have more than 4" of ground clearance. 

I tell you what...if you like what I've built when I'm done, I'll provide you with a pdf line-drawing and cutlist of materials so you can build your own!

I owe a debt of gratitude to this forum and it's members. I've received good feedback, interest and been welcomed warmly.

I hope that some of the tech, info and photos I leave behind in this thread help someone in the future to build their own dream. I've pretty much taken a hiatus from active roles in forums for the last 8 years. Work has taken up so much of my time, and many forums are toxic. It just wasn't worth it to join in the fray. What I have done is climbed, crawled, snooped, creeped and scanned my way across hundreds of forum's, websites, build threads, feeds and magazines to gather the info I'm sharing with y'all. I see farther by standing on the shoulders of giants. 

I would like to thank the gentleman who started this site:

http://www.scratchbuilt.net/

There's not much there, but what is there, is gold. I haven't reached out to him, but I should one of these days, either to check on progress, or just to lend encouragement.

I'm ambivalent.

I LURVE my 2004 Subaru Forester. It's a plain-jane 2.5 SOHC, N/A, 4EAT...but it's awesome. I've literally been in places that Jeeps fear to tread. I've been to Moab, I've taken it to elk camp, I've driven through bentonite infested roads that sidelined "real" 4x4's. It's never failed me.

My rational brain tells me I want a mid engined AWD supercar. My lizard brain tells me I want a mid engined RWD supercar.

Which do I build? That is the source of my ambivalence. And a bit of hedging my bets. What if it were possible to have the best of both worlds? Is it possible? Is it worth it?

I've done the home work and come to the conclusion that it IS possible, but it's really not worth it. I'm not going rallying with it. I'm not building this to meet a class formula. I'm too far from any motorsport activity that would make it worth the added effort and expense.

So rather than build a compromised machine, I've wondered if I could build one of each. Twice as much work, twice as much expense? I can afford $75k...I simply won't spend $150k.

So then, the matter's settled. Or is it?

Purpose built parts for one. Production built parts for the other. 

The budget is firmly drawn. So if I want both, I have to be selective, prudent, and ready to take opportunities as they come. Which means my mid engine AWD machine HAS to use ALL production parts for it's drivetrain, suspension, interior and ancillaries. It also takes a back seat to my main priority, the mid engine AWD machine.

So then, that's settled? If I never get back to the AWD, I've still got the RWD. If I wait for both, I may never have either.

So onward with the RWD build design phase.

What I've come up with so far:

Drivetrain; 6.6L LS V8, dry sump, AC/PS,  180* or 8:1 headers, ITB intake manifold, Weddle HV25 transaxle with oil pump, REM polishing and Torsen style diff, 934 CVs

LS 180* headers:

LS 8:1 headers:

Holley mid-drive waterpump mounted accessory drive:

Weddle HV25 transaxle:

Suspension; C5 cradles, C6 arms, C7 spindles & hubs, Dobbertin brackets, C6 Z06 brake calipers F/R, C7 two-piece base model rotors

C7 rear spindles:

C7 front spindles:

C6 control arms:

These are the Dobbertin brackets that allow C5/C6 suspension to be bolted on to a custom chassis:

Front suspension brackets:

Rear suspension brackets:

Front and rear brackets back side:

Rear suspension:

Front Suspension:

Link for Dobbertin brackets:

https://rick486.wixsite.com/dobbertinperformance

Chassis; steel tube spaceframe/semi-monocoque, rollcage 1.625" DOM, main spars F/R 2x4" .065" wall, bottom rails and truss bars square 1" .065" wall, floor panels & firewall F/R .065" steel, close out & access panels .090" aluminum

Gordon Murray iSTREAM chassis:

Gordon Murry "ultralight" iSTREAM chassis (aluminum):

Spydercars new chassis replacement for vintage Lotus cars:

Lister Bell replica Lancia Stratos' chassis:

JBL replica Cobra monocoque chassis:

I really like Gordon Murray's i-Stream chassis designs. I'm going to strive for more of that design with my chassis, minus the composite panels bonded to it. My panels with be steel & aluminum.

In reply to Gingerbeardman :

Hopefully you have a facebook account, because the only source I have for the second version of his car is on his account there.

https://www.facebook.com/superchicken237/

https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/letting-the-chicken-out-of-the-bag/150651/page1/

By the way, I think the reason your thread has taken off so well so far is that we all have similar dreams to build our own cars to our likings. Depending on how the next year goes, I may start my own build... Until, I'll live vicariously through yours!

I am enjoying the porn in this thread!

Not trying to be negative here, but as someone who is involved in research and development for a living, its the development part that scares me when it comes to building my own chassis. How do I know if I got it right and what will I do when I figure out that maybe I did not?

My fallback is to use systems from other cars that have been well validated and verified for what they do. Try not to mess with the specifications and hope that the results are predictable based on the OEM application. This of course leads to sticking Corvettes or some other high volume, high performance chassis with known performance evelope under a pretty body of your own design. Nothing wrong with that but you want to go further down the design tree to make it your own design. Looking forward to following along and learning stuff as you go.

I don't know for sure what this tub is, but I sure want to build a car around it using Vette suspension parts and LSx power. It has the look of something that was built with CATIA by someone who has a lifetime more experience than I ever will and maybe some tooling that mere mortals can't play with.

As far as the body, I would break out the E-wheel and make scrap until I was happy with the results. That kind of development I can relate to!

I Hope I didn't Insult your build by Suggesting things can be done on the Cheap. In the 60's when I started Hanging around Racing there were Two Classes of Heirachy , those with Factory Help And Everyone else, learning to do More With Less Was A Priority.

    If you like that Tub it appears a Corvette with a Nice cage and Cup car like door bars, No Matter, to copy that if you know the Fiero/Corvette tubs look then at Jegs race car Roll cage for a fiero and the fit but for door bars is almost Identical, And not bad Money wise at 600 bucks. your picture has a Bolt on front suspension, no clue what sub stucture attach's that way

In reply to WillHoonForFood :

OH MY GOD...that thing is EFFIN' AWESOME!!!

How in the hell did I miss that build?!?

Isn't that guy friends with another gentleman that turned a NASCAR chassis into a hillclimb car that won nationals a couple of times?

Yeah, I've been living vicariously through other peoples builds for almost a decade, so I totally relate. I'm hoping to push my skills forward by building to a higher quality than I do even at work. I want it to be functional art...without a pedestal, without being precious about it.

In reply to NOHOME :

This is a chassis designed by Gordon Murray, part of his iSTREAM platform (specifically this chassis was built for a mid engine car using a Yamaha powerplant...it debuted at an international car show 2014-2016?)

Part of my motivation for building the chassis out of steel is it's a known quantity for me. I've worked with it for over 20 years. I know how to bend it, shape it, cut it, weld it, even heat treat it. I know it's tensile strength, it's yield strength and it's ultimate strength. It's ductile, not brittle. It's literally one of the words we use to describe strength and durability. We compare other metals to it, and composites to it. Steel has built the 20th century.

Rule One when doing something that you're not sure about...start by copying someone else 

Rule Two...research and find best practices...copy said best practices.

Rule Three...basically a wash and repeat of Rule One and Two for all the steps that follow. 

A basic understanding of engineering principles helps. But basically, as long as your welds are sound, the steel itself won't let you down. You might learn you've built something that's not very stiff...so your chassis acts like a giant spring. You might find you've added 200 lbs. MORE steel than you actually needed, making it heavier than necessary. For myself, there are many examples of chassis that are a known quantity, so I'm not terribly worried. I'm not inventing anything new, just a different interpretation. Think of it like jazz.

Hell, look at Colin Chapman's original Lotus 7...or pretty much ANY of his road cars built while he was alive. They aren't exactly the most robust things. Or, look at the Maserati "Birdcage"...a car that had multiple redundant tubes that didn't actually carry loads, while load paths traveled through sections of the chassis that were unsupported. And somehow people think THAT is an example of a good chassis.

Fortunately my stint in NASCAR gave me some experience with just how good some simple DOM tubing can be at keeping drivers safe and inside the vehicle while it's turned into an accident-cum-adventure-ride.

In reply to GTXVette :

Not at all! I didn't take it that way.

I know things could be done less expensively than how I'm doing it...but not by much when you need a transaxle that can actually handle V8 torque and a strong mid-range power band, especially when you gear that transaxle like a regular transmission found behind that V8.

The Weddle HV25 is $9500. That's actually LESS than what an inverted 996 gearbox with adjusted gear ratios cost. AND I can pick from a plethora of available ratios to gear it for MY specific engine powerband and use. If that transaxle had come out 10 years ago, I would probably have kept the GTM and this build would be a "rebuild" of that chassis for my new design.

That bolt on front suspension is what you'd find in C5/C6/C7 Corvettes. The lower control arms bolt to the aluminum subframe and the upper control arms bolt to the chassis rails. The aluminum subframe then bolts to the chassis rails. The brackets I showed up there are a product from a guy by the name of Dobbertin that allows you to use Corvette suspension as a bolt-on affair on a custom chassis using commonly available rectangular tubing.

Dobbertin is an interesting guy, he built a Pro Street car that was on the cover of Hot Rod in the late 80's/early 90's, he also built the Surface Orbiter, a fuel tanker trailer that he turned into an adventure mobile and drove around the world in. 

My reasoning for going with C5 cradles...after talking with Ron Sutton about my build, he said that the C5 cradles have better geometry than C6 or even C7 for what I'm after (even though he feels they may be too compromised for what I'm after...but he's used to $100K+ ProTouring builds).

Why C6 arms rather than C5 arms? They have some added tweaks that make them better than the C5 and I feel like they look better than the C5 stuff.

Why C7 spindles and hubs? The spindles on C5/C6 are the same, front to rear - front right, front left, rear right (front left turned around), rear left (front right turned around). The spindles on C7 are dedicated to each end of the chassis they serve. C7 rear spindles have better toe control placement and toe arms are a better design than that on C5/C6. C7 hubs are equivalent (actually better) than the C6 ZR1 HD hubs...and cost less than $100/pc. They also don't have built-in ABS sensors.

Good luck on your build!  I'll be following .l

 I've used C5 cradles and suspension for a few cars. For one I kept the stock wheelbase, built an all aluminum tub to which the cradles bolted to and made a couple of interchangeable bodies for it.  I also shortened the torque tube by 23 inches and moved the engine rearward.  The finished car weighed in the 1600's.  Most awesome driving car that I every had.