Trans Am Corvette & Grand Am Rolex Corvette?

[pgtr]

How different or similar are these in configuration, construction or performance?

I think the TA Corvettes (or Jags for that matter) are tube framed scratch built race cars w/ silhouette bodies. They run solid axle rear ends and carbureted Chevy SBs (well Jags run Fords I guess). (this sure seems awfully reminiscent of the NASCAR formula)

I 'thought' the Rolex series allowed for Corvettes to be entered & could also be be tube frame chassis but beyond that I dunno! In fact I don't now what Corvettes are even running in this series off hand.



thanks,

[noise boy 2]

Both are really the same car, that is a tube framed scratch built race car. They could be anything you wanted all you have to do is change the bodywork. The GA version is the same, just adds lighting. Robert

[weeks]

your right about the Trans-Am vetts, but the Jags do infact have engines from Jaguar. There are 2 types of Grand-Am vetts. The ones in GTS are Trans-Am cars but with lights and less power. The vetts in the SGS(super grand sport) class are similar to the ones you see in Speed World Challange.

[Splatz the Cow]

eh?

I'm pretty sure the GTS cars are 7 Litre, different from the TA cars considerably.

[pgtr]

Thanks again!

The Trans Ams run Chevy small blocks (I 'thought' the Jags ran Ford SB V8s but stand corrected - taht's just what I had heard).

But I didn't know the Rolex GTS Corvettes ran 7Ls. What about their rear axles? Are they solid axles like the Trans Ams or something more exotic like independent rear suspension?

I suppose the 7Ls in the Grand Am Rolex Corvettes would put them up a notch on performance no?

I've always referred to both teh World WC and Grand Am Cup Corvettes as 'Z06' and essentially considered them to be the same and highly stock/production based. (I have to admit watching this form of production based sports car racing is really catching my interest! - but that crash a few weeks ago in WC GT - ouch!)

[pgtr]

This is interesting... I missed this the last time I was there but found it this time.

It seems BOTH tube framed Corvette bodied cars AND PrattMiller C5-Rs are approved for Grand Am GTS!

Very interesting...

Excerpts from the official grand am site follow...
http://www.grandamerican.com/competi..._GTSrules.html

1-2 GTS-approved Production Based (Unibody) Cars – Normally aspirated engines - maximum displacement 366 cubic inches. Approved *Turbocharged engines - maximum displacement listed below.

1-2.1 Corvette – Pratt & Miller C5-R

...

1-3 GTS-approved Tube-Frame Cars 1998 to 2003 body styles

1-3.1 Chevrolet - Corvette, Camaro and Monte Carlo

[Chevyguy]

ptgr, you're not crazy, the Jags did use Ford V8. I believe this is the first year an actual Jag engine is in the car.

[billnchristy]

The jag engines havent been used yet, it was announced, but they still arent "installed"...

As for GA and TA cars, the TA cars use 315cu in engines with high compression ratios (13.1 i think)

GA engines are regulated by weight

Up to 340 CID - 2500 pounds

340.1 to 362 CID - 2600 pounds

362.1 to 382 CID - 2700 pounds

GM LS6 or Ford Mustang DOHC Modular 4-valve V8 engine - 2400 pounds.

[billnchristy]

Oh yeah and GA cars are about 100 or so HP down on T/A cars, but pretty much do run similar drivetrain components

[billnchristy]

I was off a bit on the T/A engines, they are generally 311cid upto 358 (the GT1 spec) and you can actually run a 4valve but it has to be like 250cid...there are specific fuel req. for each size engine also, check out the technical specs on the T/A official site...

[Fogelhund]

Originally posted by pgtr
This is interesting... I missed this the last time I was there but found it this time.

It seems BOTH tube framed Corvette bodied cars AND PrattMiller C5-Rs are approved for Grand Am GTS!

Very interesting...

Yes, but.... not with the engines they are currently using. They are mandated to run 6l engines under Grand Am rules.

[noise boy 2]

My post applied to the cars that are actually running in GA now, I didn't realize that the C5R was Homologated for GA, but there are none of those running there. The GA GTS Corvettes are all former TransAm cars currently. Robert

[billnchristy]

I think the only reason the C5R is in the rules is because the time they ran at the 24hr of daytona with Dale Earnhardt and son...

[Racecar Mike]

As the crew chief for the Derhaag Motorsports Corvette that was the fastest qualifier at Daytona this year (yet started seventh... go figure), I may be able to shed some light on this subject. The car we ran at Daytona (chassis 006) was purpose built in house to Grand Am rules. The basic chassis is identical to our Trans Am cars, but has different uprights fitted for larger brakes in the front, with the same size brake components in the rear. Bodywork is identical save for rear wheel arches. All de rigeur endurance equipment is fitted (lights, refueling gear, airjacks etc).
Engine rules are quite different. Our Grand Am engine package is 373 ci with a 600 cfm carburetor, mandating a dry weight of 2700 lbs. Aluminum blocks are allowed in GA. Our endurance spec engines have cast iron blocks by GM Motorsport, and are not production Corvette based. Trans Am engines are 310 ci with a 750 cfm carburetor. Aluminum blocks are not legal in TA, but the GM "Shortdeck" blocks are allowed, and this is what most Trans Am Corvettes run currently. In this configuration, the dry weight of the car is 2650 lbs. All of our engines are built by CRD. To paraphrase Rolls Royce, TA engines make "adequate" power, while the GA engines have "more than adequate" power. Both cars have a live rear axle with a Detroit Locker diff mandated by the rules. The TA cars have an aluminum cased diff while the GA cars use a steel cased unit. The GA car is much faster than the TA car owing to the larger brakes, larger tires, more power and slightly more downforce. Relative to the IMSA/ALMS cars the TA/GA cars have much less downforce and more drag as well, and this is where the much of the difference in laptimes shows up at Road America which places a premium on good L/D.
Our qualifying time at Daytona of 1:49.0 with Justin Bell at the helm (on race gearing and a "slightly higher than race" rev limit) stands up well to the times posted by the Pratt & Miller cars. I would love to see tubeframe cars allowed in ALMS to give a more direct comparison. I think some people would be very surprised...
I hope this helps.

[gttouring]

wow Mike
welcome to the forums and please come back often, I for one would love to hear more 'indider' bits and good technobabble. As a struggling racer/crew chief/mechanic myself it all is good to read...

[gttouring]

imean insider not 'indider' whatever that would be

[pgtr]

Indeed RaceCar Mike! Thanks!!! I posed the original question and this was an incredible 'keeper' of an answer.

thanks,
-T