Just cut away the fiberglass layer on top, and there is real steel below it. I put a 5 point roll bar in my car, and it wasn't a problem.

 

Even though its not required I'd still put a bar from one side to the other on the front of that cage. Otherwise that cage will definately work insde a C4, make sure you use a cage builder that has done a NASA or SCCA cage. Make it strong and safe, have fun with this!

 

I'd add bars up to the front frame rails and the mentioned dash bar as well as a harness bar and seat rails.

Also - make sure whatever cage you build is good for the unlimited class too - I dunno if they have different requirements for the classes but better to be safe!

As for the suspension - I'd just fab up some steel A-Arms - make a jig from the stock one if you're trying to keep the stock geometry - plus once you have the jig you can make replacement ones for the ones that get bent when you run off the road and smack a tree or boulder

I think we all want to see pics when you get this thing going!

 

I plan to do most of the cage work myself with a few TIG-welding buddies, and I'm sure over the next year or so I'll have a few crash nightmares and thus add extra bars until no more will fit in the car (or until I don't fit in the car). Those pro WRC guys crash often enough, let alone an amateur driver in a poorly suspension-tuned, much more powerful, RWD car...

And yes, if/when I do the build it will be thoroughly documented, mostly to try to get a few more 'vettes out in the rally world.

Anyone have any good pics of a C4 stripped down to the "frame" in prep for a race build? I've searched the net in vain... a good set of pics would help me visualize the suspension and cage designs. I need something to feed my daydreams for this week!

 

Recently there were some frame PDF's posted, I'm sure a search will find them.
Also IIRC there was someone selling a couple of c4 frames in the for sale section.

Good luck!

 

In Finland that's nothing new, they've been doing it for years.

http://www.ralli.net/foorumit/rata-o...10175?start=15

And that's no coincidence, Finland has produced more world rally champions than any other country in the world.

 

Thats pretty cooooool!!! Any more pics?

 

the c4 is sketchy on gravel. the leaf springs crack if you jump them {ask me how i know this} you could do it but awd/fwd is generally easier to drive on loose terrain. if you do a c4 switching to coilovers and putting a steel plate in the drivers side floor pan would be smart. the fiberglass floor pan doesn't take a lot to penetrate. a tree branch could seriously injure you

what are your limiting factors for the sub 3L 2wd?

my natural thought is to use an integra for a few reasons, i'm not just bias since i use one as a DD, the benefits are

1. a stable car
2. great transmissions are available, the type r uses a helical LSD and tight gearset
3. engines are everywhere from japaneese importers
4. rally tires and suspension have been designed for it
5. entry cost is low since an engineless shell is maybe $1500-2000

the only drawback is that they only use 1.8L which is a big disadvantage to a class that allows 3L, still, with rally, hp isn't everything and the type r milks 200hp out of that 1.8L all oem correct which is nice if you're mod limited

 

First off, that picture is the first I've ever seen of a rally C4, and it's epic! Any more info/translation you can provide would be awesome! And fortunately, I am something like 50% Finn so I should have a bit of that rally blood in my veins .

I could argue many of those points, but a restatement of my goals is easier:

1.) Build a rally car that is fun to drive and work on (hence RWD and a 'vette)
2.) Re-engineer and fabricate the entire suspension and drivetrain to use durable and tunable components (double-As front and rear w/coilovers, LSX, seq manual)
3.) Have waaay too much power (Group 5 is limited to 6.3L with a pushrod engine)

The fiberglass body thing is definitely a concern from a tech-inspection point of view. I need to contact a rally "scrutineer" to ask if the firewall, fuel bulkhead etc. can be 'glass and still satisfy the intent of the rules.

 

On another, separate point:

I've done a bit of research and it appears that no company makes rally-specific tires (which you DO need to be competitive) in anything other than a 15" wheel diameter. Does anyone know if it's possible to cram a 15" front wheel over the stock C4 brake setup? I can find pictures that make it look feasible, but there's no substitute for someone having done it (although I have no idea why they would have). Anyone given it a shot?

 

Build a steel floor pan.
Would not be that hard to do if you have a sheet metal brake.

The C4 has Very strong side frame rails.
The front frame horns are Very strong too.
Have seen C4's desiccated apart.

Frame and suspension on a C4 are still superior to any other run of the mill car out there I believe other than the C6.

Leafs springs could fail. But the frame wont easily.

Properly designed roll bar with a Full halo over the driver's head is a must. Just in case the car happens to flip over.

 

you're class limited to 3L for a couple years? i think you have the vette thought out well but how about until then? i mean that's a lot of racing to be done. the best sub 3L rally car is probably the wrx or evo but then you're into awd. beings your next race is sub 3L of displacement i just figured that's where you would be focusing

also if your focus is on winning with the vette the power production is something you'll have to be careful with, it's REALLY easy to overpower available traction on broken terrain. spring and dampening rate along with ride height are going to be big big deals

 

the front is really good.

the rear....well the rear would really benefit from poly bushings at a minimum. high speed impact distortion from broken terrain is going to be hell on the half shaft u joints.

 

I'm limited to 3.0L and 2WD until I gather a certain number of points by completing events. My current plan is to buy a BMW E30 325is, bring it up to safety spec with cage etc., and just race it in stock config until I can go 'vette. I'm not concerned with winning with the beemer as much as just getting the hang of RWD driving in a rally situation.

The 'vette would be FTW, though, so yes, my driving skills will be taxed in a high-powered RWD car. But it's doable... check youtube for vids of the last few years of Rally Group B before AWD came around... those guys were running 600hp in rear engine, rear drive cars which are even harder to control than a F/R configuration. It can be done.

 

Have you progressed on the rally corvette project?

We are stage rallying a Corvette C3 in Europe in historic events (FIA European Championship). The Corvette is a very good rally car indeed.

While we are only doing tarmac stage rallyes, in the US almost all rallyes are on gravel roads. But even on gravel I am sure that a C4 should be one of the best rwd rally cars you could get. An early C4 should even pass for the historic class of Rally America (25 years) ...

Anyhow, even on gravel you will not need a foot of ground clearance and specialy you don't need a Blazer or similar. With something like standard heigth or maybe 1/2 or max 1 inch lift you should have enough wheel travel and ground clearance.

Weight will be the major issue ... but there are ways to bring a C4 down.

Regards from Switzerland and good luck with the project!

 

Integrate a Syclone trans system and make it all wheel drive.
Its been done

 

I have a question for you:

why not choose a c3 or c5 as a rally car?

C5 prices are in the toliet also (like c4 prices).

Plus, you also have the lsx engine already in there. ...im just saying.

 

I am following this thread with avid interest.

 

A C4 rally car would be unique and cool.

With that said, you are going to have a lot of cash tied up in building it. One other avenue to consider is picking up a used Bush or ARCA car then start modifying the suspension to suit your needs if that is allowed in the rules. You have the best cage available, fire suppression, dual ignition systems, fuel system, brakes, etc.. Rollers can be had cheap (< 10k). Complete cars with fresh 800 hp engines can be had for 20-25k. Racingjunk.com to find them.

 

Well here is a topic for me. I've spent most of my adult life making a living in Rally Racing here in the US. I worked for John Buffum for 8 years, Subaru Rally Team USA for another 6 years and well as various top privateers. I've also owned 6 C4's over the past 16 years.

This is indeed a case of using a car for an unintended purpose. That being said just about anything is possible and with some work the C4 might be reasonably competitive in stage rally. You are however going to face a number of hurdles:

In Rally the more suspension travel the better. You are going to want to get the most possible suspension travel possible. Forget the transverse leaf spring. You also want a relatively soft suspension to help keep the tires in contact with the dirt. 80+% of Rally cars out there are over sprung. You will need to install coil overs. One trick you *may* be able to do is use spacers between the subframes and body to increase room in the wheel well for wheel travel. May get a bit tricky with the C-beam, shifter, etc etc but the increased suspension travel would be well worth the effort if this can be done.

you will need to use 15" Rally tires so you will need to address the brakes. A nice set of Wilwood brakes can be fitted without too much trouble that will clear 15" wheels.

Plate the floors with either aluminum plates or maybe Kevlar. I've seen rock blast wear through the floor pans on conventional steel uni-bodies. The fiberglass pans on a Corvette would be shot in no time. Also, A rock could easily puncture the floor plan in an off so, this is a mod for safety as well.

In most Rally cars once the car is stripped and being caged the uni-body panels that make up the body shell are all seam welded for strength. Metal bosses are welded to the chassis replacing the plastic fasteners manufacturers use. The Roll Cage is ideally tied into the suspension points and strut towers to greatly strengthen the car as a whole. Unfortunately the Corvette is fiberglass. Much of the car is bolted together with self tapping body bolts, plastic screw grommets and self tapping screws. It's going to be difficult to keep the car together. Maybe bosses could be fiberglassed into the body?

I don't to dissuade anyone from pursuing their dream but understand that preparing the C4 for Rally will represent challenges both numerous and unique as compared to most other cars. While the car has some inherent shortcomings which would likely keep it from being the most competitive car in it's class it would make a fantastic looking Rally car and should prove very, very fun to race if it holds together.

The only Corvette Rally Car I ever recall seeing in competition was back in the early 2000's when a guy showed up at the Maine Forest Rally in a C3 Corvette. The guy had a cheap C3 and wanted to give it a run. IIRC the challenge that ensued was to simply make it to the finish. It was missing most of it's body panels by the end of the 1st day. I also remember the car was absolutely filled with dust (something good construction techniques can eliminate). Who knows how well the car was prepared. I don't recall ever seeing it at a Rally again.