I've been asked to complete the build of a friend's 1990 'vette. It has now been caged by a local expert and it has serious performance with a Dart-blocked SBC with 540 HP. Did I mention it is about 2 feet shorter than a stock-bodied C4? It's body has been crafted by a CF expert to remain true to the original shape, but it is now MX5-sized! The owner can fit nicely inside the car, but my bulky 6' will not. And it currently has a small fuel tank of about 6 gallons. He had used it as an AX-only car until now. Somehow I will have to find space for as much fuel as possible, and still get it certified by SCCA.

It will need at least 30 minutes at an average race fuel consumption estimated with BSFC of .6 LB/BHP*HR. although real world numbers may be quite different.

So, here are my initial jots on a napkin... .6 BSFC X 540 BHP = 324 LB / 2 = 162 LB / 6 LB/Gal = 27 Gallons!

I will receive the car in a few days and then the tape measure gets warmed up...

Does Fuel Safe or ATL make custom tanks with SFI approval? Are multiple-cell tanks legal?

Before you start working on the C4 Vette, your friend needs to check with the regional club racing officials to see if the vehicle is even certifiable. I say this for two reasons: first the scaled down version of the 1990 Vette if the wheelbase was altered; and second the custom cage work you described may not meet SCCA standards. Additionally, what class was the owner interested in - GT1 or ITE? Two very different classes with different rules on fuel cells. (ITE is a regional class so the owner must check with the region for the specific rules. GT1 is a national class and it's specifications are listed in the General Competition Rules.) (For GT1, the fuel cell rules start on page 98.)

I'm not sure that mulit-cell fuel tanks are legal in classes other than Stock and Touring if the original car came equipped with saddle bag tanks. Again, please check with the regional racing officials as they will be more up-top-date on what's legal and what isn't.

Good luck! (IMG:http://www.frrax.com/rrforum/style_emoticons/default/beerchug.gif)

Thanks for that.

We are in Canada. The CACC is our local affiliate of ASN Canada and we do things a bit differently up here. We do use SCCA preparation rules (by reference) for SCCA GT-equivalent classes for instance. We also have local classes such as GT-O. I periodically run in ITE in Northern California and those rules are very similar.

We won't build the C4 to GT1 because its body won't meet the rules in either Canada or the US, although the changes do not include any wheelbase or firewall alterations. GT-O allows any engine Over 4000cc (that's the "O") in almost any car you can think of. Tube frame cars converted from left-turners, Pontiac Fieros with rotary engines, and 5-series Beamers and RX7's with LSx engines come to mind. Rules are flexible but safety items are generally the same as the GT-1 class preparation rules, as these cars are just as fast or faster.

The cage has been done to GT-1 standards by a very capable specialist who knows the current rules. I'm still waiting to see what I'll run up against with the fuel cell issue. I just hope we can get enough fuel into this thing, and still meet the safety rules for cell installation. I know we'll need an approved cell, so I hope one of the companies can build something that will fit the space available. I already warned the owner that this will be the biggest hurdle to get this thing legal for roadrace.

Just curious; are the front clip and/or the rear section tube framed?

ATL will build you whatever you need. Bring the checkbook $$.

I'll let you know when I see the car without the panels. After some discussion, the owner may be changing his mind!

Fab a can that fits in the space available, Fuel Safe or ATL can build a bladder that fits the can. A single cell is way less complicated to plumb, even if it needs multiple pickups. Since the rear crush space has probably already been eliminated, I'd look at cutting out the tubs aft of the seat bulkhead and doing a saddle shaped cell there with an internal low pressure transfer pump.

Thanks, yes the rear space is gone from what I've seen. I'll see what I can do.