Dr L-88

I am curious as to why MOST of the C3 race cars were convertibles, even though many of the convertibles ran with a hardtop. There just doesn't seem to be that many coupe (T-top) race cars from the 68-72 era. Is there any particular reason?

Thanks,
Rex

MelWff

easier to put in a full roll cage in a convertible?
visibility to the rear when using a wider rear view mirror?

mikem350

Well, one reason is that MORE verts were built....

71 Green 454

Wasn't there 22,339 more coupes built from 1968 thru 1972 model years? 77,909 Coupes vs. 55,570 Convertibles.

1968 was the only year that more Convertibles were produced than Coupes: 18,630 Convertibles vs. 9,936 Coupes.

Pop Chevy

Less weight to deal with.

Syl1953

I may be mistaken, but I believe convertibles weighed almost 30 lbs. more than coupes in 1970, don't understand why or how though. Mark

Richard Daugird

I was under the impression that most ALL cars were heavier in convertible form...

C3Paul

I think, convertibles were cheaper than coupes

Richard Daugird

THAT would be a surprise.

René K.

In fact, convertibles really were cheaper... around 10% (checkout the Corvette Black Book). As C3 convertibles have no specific frame and just a few reinforcements in the body but less structure parts and birdcage due to the missing roof they also should have less weight than coupes. Also, I assume the modification of a convertible to a race car seems to be easier. Finally, I could imagine that a convertible with hardtop might offer slightly more headroom for drivers with helmets.

However... that is just my thoughts...

Richard Daugird

That all makes sense Rene.

JC68

As hard as it is to believe today, yes the coupe cost more than the convertible in 1968. Coupe base price was $4663, convertible $4320.

The weight of a convertible with the hard top only is almost identical to the coupe. According to GM specs it is 10 pounds difference. I forget which one is actually less. A convertible with a soft-top weighted approximately 50 lbs more than the coupe.

The reason most race cars were convertibles is they were available to be bought right away. Coupes didn't go into production until late Dec/Jan time frame.

Also the convertible with hard top has better aerodynamics than the coupe. The vertical rear window is bad for aerodynamics.

John

mikem350

I believe the hardtop was an option, jacking up the price...

Calo69

Maybe somebody knows if different sanctioning bodies allowed certain body styles and the convertible would be eligible for either, open or hard top.

JC68

In the convertible base price you got to choose either the hardtop or soft-top. If you chose the soft-top you could add the hardtop on top of that as an option.

John

gbvette62

This was discussed on here a couple years ago. There were some people who insisted that the reason was that it was easier to put a cage in a convertible, but that's not right. Cages had nothing to do with it, because all that was required in the 60's and 70's was a roll bar, not a full cage.

As Pop and Rene said, it was because they weighed less, but also because of aerodynamics and weight balance.

In base production form, a coupe weighed about 150 pounds less than a convertible, but once stripped and prepped for racing, I believe the convertible weighed slightly less. Much of the weight difference was the convertible top frame, which was removed for racing. Even if a car was running a hardtop, a gutted hardtop was lighter than a coupe body, with the added weight of it's birdcage.

The convertible body was also more aerodynamic. At one time, production cars were allowed to race, without a windshield. The convertible body is much cleaner aerodynamically without a windshield, than a coupe would be. Even with the tops and rear window removed, the coupe's targa bar creates a lot of aerodynamic drag, and also disturb the air flow over the car. A convertible with a full windshield, is still aerodynamically cleaner than the coupe, and the convertible's hardtop, with it's angled rear window, is also better aerodynamically, compared to the coupe's vertical rear glass.

Finally, with any race car, you want the center of gravity to be as low as possible. The coupe's birdcage puts a lot of extra weight up high on the car. Because it doesn't have a birdcage, the convertible body has a lower center of gravity.

When we went SCCA racing in 80, these were all things we considered. We were coming out of SCCA Solo, and moving up to GT-1. The SCCA had just gone from the old B Production rules, to the new GT-1 classification. At the same same time they changed the classes around, they also changed the GCR, requiring all production cars to run a full windshield. Unfortunately, they grandfathered in older cars without a full windshield, allowing them to continue to race without one. That put anyone building a new car, at a disadvantage, at least aerodynamically.

The GT-1 rules allowed silhouette racers (a tube frame and a fiberglass skin), so we didn't have to run a stock birdcage or any other stock structure. We elected to build an 80 coupe, with it's fastback rear window. We used a stock Corvette frame, with a full cage that tied the whole frame together, front to back. I think the only part of the stock body structure we saved, was the cowl/hinge pillar area. The rest of the car was just a light weight fiberglass skin, in the shape of a 1980 Corvette.

Our two main competitors here in the Northeast, were Ken Slagle in his Triumph TR8, and Paul Newman with his Datsun 260Z's. Slagle's Triumph was grandfathered, so he didn't have to run a full windshield. As can be seen below, without a windshield, that car was quite slippery! With Datsun factory backing, and a full compliment of sponsors, Newman's budget for a weekend, was more than our's was for a whole season. Even so, Jerry (the driver I crewed for) was able to compete with them, even if we rarely finished ahead of them.

From the pictures below, it's not hard to see which car is going to cut through the air better, Slagle's TR8, or our Corvette.

Gale Banks 80'

I agree with the above. When the 68 came out it was proven that the Hard Top was more Aero than the Coupe. I happen to have a 69 vert that shows a lot of signs to be an L-88 car. One of the bigger clues is that it is a Hard Top soft Top delete car.

3JsVette

better aero

694speed350

They were and actually lighter.