1966 Corvette Convertible SCCA race car #77 ASR

by Mike "Doc" Cobine
70373.2450@compuserve.com
cobine@cig.mot.com
Procrastination Racing, Deerfield Beach, FL & Lake Zurich, IL

Body:

In these days of restored Corvettes, this car is almost sacrilegious. However, its transformation into a race car occurred long before anyone had an idea of restoring Corvettes, when the value of a Corvette totalled after an engine fire was virtually nothing. Originally it began life as a Sunfire Yellow '66 convertible, but there is so little of the original car that it is unknown what engine or transmission was installed, although a guess would be that there was a 4 speed, since it was a manual and 4 speeds were more prevalent. I'm only guessing the engine may have been a 427 since a big block core support and radiator were with the car, based on the idea that existing parts were used but there is always the possibility that the larger big block radiator and core support were substituted for the small block version.

As many poor Corvettes, this one suffered the indignity of being totalled out by a Miami insurance company in 1970 due to an engine fire. The car was purchased from the insurance and converted into an NCCC race car. It was sold around 1977 in Jacksonville, FL by Jim Wilson, who apparently was a Corvette dealer of the time. The new buyers took it SCCA racing in the A Sports Racer class due to the extensive modifications beyond the Production rules of the time. They raced at tracks like Gainesville, Palm Beach International, and Sebring, running an assortment of engines. If anyone remembers a black and gold (Smokey Yunick colors) '66 convertible racing back then, I'd be happy to hear from you.

In its original form as a race car, it featured both a one-piece tilt front end and a tilt rear end for access to the engine and suspension. The L88 flare fenders were at all four corners to cover the 11 inch wide race tires on 10 inch wide custom made rally wheels, which were held on by 5/8 inch Moroso studs. The car ran an assortment of engines, from 327 to 454 depending on the interests and the availability of its owners. A full cage was installed with a center bar (about where the center bar of a T-Top on '68-up would be). Also installed was the dual pin brake system, including the proportioning valve, endurance pads, caliper spacers, and special offset caliper brackets. The windshield was removed and replaced with a 6 inch high plexiglass windscreen. The dash and glove box were removed and replaced with two aluminum panels holding the needed S-W gauges. This is where I took over.

Stage 1:

When I got the car, it was missing the front end, the engine, and the transmission. A discarded '63 front clip was pieced together with '66 side louvers to make a removable front end as the hinging mechanism was also gone. The front end was cut at the fenderwells and 4 inch wide flares added. Yes, this hurt me as much as you, but it was necessary for the character and purpose of the car. These covered the 10.5 inch wide slicks that were mounted on 8.5 inch wide aluminum slots. In the rear, the existing flares covered the 12 inch wide slicks on 10 inch wide aluminum slots. In this form, it ran with a 350 and with a 402. The front clip is held on by two 3/8 inch carriage bolts that thread into the radiator support and by 6 Dzus fasteners at the rear.

Initially, the rear clip had been held down in front by only a few Dzus fasteners. I fiberglassed in a metal plate on each side and mounted hood pins to the roll cage so a more positive restraining system held the clip down. The block-off panel that separated the rear suspension from the driver's compartment was originally behind the cage, allowing the cross bracing to be in the draft. I moved the panel to in front of the cage to make a smoother area for air to flow past.

The rear deck lid had been glued in place and was separating. It was too short to close next to the roll cage and left a large opening. I extended it forward to close the gap at the roll cage and reinforced the lip for added rigidity. I ground out the old channel where the lid was glued to the clip and glassed it together so that it became one piece.

Stage 2:

After some time with the car, I learned that much weight could be shed in several places. One such place was the header bar that previously held the headlight assembly. This provides the rigidity for the front clip so after I removed the metal bar, I made a fiberglass channel that was as stiff but many times lighter. In sections where I had difficulty forming the channel, I used pieces of styrofoam and glassed over them. this makes a very strong and rigid channel that is much lighter that the steel under there stock.

I also removed the frame from the hood skin. While this seems to be silly since it is already fiberglass, the removal made lifting the hood much easier. To keep the hood stiffness, I made one small but deep fiberglass channel across the width of the hood underneath by using a 1/2" PVC pipe and glassing over it.

The factory core support and radiator were discarded as they were marginally cool for a small block and marginally hot for the big block. An aluminum support was fabricated and a 4 inch thick aluminum radiator was installed, mounted upright instead of angled. In retrospect, a 3 inch or 2.5 inch aluminum radiator may be sufficient since the thickness makes getting air through a problem. An electric fan helps. a duct to the grill opening was made so that air entering the grill can only go through the radiator and not off to the side.

Inside, the racing seat was braced by an additional brace near the shoulders as required by the rule changes. Three inch shoulder belts thread through the seat back to the cross bar on the roll cage. A 3 inch lap belt and 2 inch anti-submarine belt are also used.

The fuel cell was relocated slightly forward and lower with an aluminum bulkhead installed in front of and to the sides of it. The bulkhead provides protection from the fuel and support in the center of the rear deck in the event anyone should inadvertently sit on the car.

Stage 3:

When the 427 L88 was planned, modifications were also made to the body to help it use the extra power. The front flares were extended wider and down into an integrated front spoiler, similar to the Pontiac Trans Am. The front parking light housings were shaved off to make this easier and to smooth the air flow. The rear flare fenders were split and extended outward. All of this was to cover the wider slicks of 12.5 inches in front and 14 inches in rear on 16" x 12" wheels. The spoiler was needed to help hold the front on the ground, and planned to use an additional aluminum spoiler on the lower edge. At speeds of 170 to 180 mph, the front end is extremely light even with these modifications. Without the front spoiler, it would have been impossible to handle at 180 mph. No rear spoiler was used as it would make the front even lighter. This was a lesson learned by a fellow competitor in a '67 Corvette who had only a modest front spoiler and a full GT1 style 6 inch high rear spoiler. At speeds of 150 mph, his car was nearly impossible to handle. The '68 up body was much better at high speed than the '63-'67.

The transmission tunnel had been cut by a previous owner with several large holes for access to the shifter and transmission bolts and covered with metal. I cut the entire tunnel out from the bellhousing to the yoke similar to some British cars such as the TR-3. After patching all of the holes and extending the side to clear the Hurst shifter, I added Dzus fasteners to provide quick and easy access to the transmission.

Future Plans

As the rules are ever changing, there are new items that are planned to be installed for the 1996 season. A FIA approved fuel cell will replace the bladder tank presently there. While the bladder tank is technically a fuel cell bladder inside a steel enclosure, the rules now require the cell be FIA FT3 approved and that includes having foam baffling.

A new on-board fire system will replace the 5 lb. fire extinguisher currently in place. The new fire system will have nozzles in the driver's compartment and the engine compartment and be operable from the driver's seat.

Suspension:

The suspension components are similar to parts sold by Dick Guldstrand in the late '60s and early '70s and may be his pieces. However, the parts were fairly simple to fabricate and I would be reasonably sure that copies were available from many sources. These parts should not be used on the street. They have no give to them and provide a solid connection, so that vibration and noise are induced through the entire car. Also, this places stress on components since all vibration is constantly shaking the entire car. The solid bushing have grease fittings and must be maintained regularly since dirt will cause extreme wear and the part will fail.

The rear suspension included fulled adjustable toe-in bushings rather than stock or solid bushings. The trailing arms are offset and minus splash shields or emergency brakes. The rear differential is held by solid aluminum mounts at the propeller shaft and the crossmember ends. The camber of the rear wheels are set by a Heim jointed adjustable rod that replaces the stock camber rods. These have been sold in many forms from many companies, if you wish to duplicate the same today.

The front A-arms are mounted on aluminum offset bushings. These bushings change the camber by moving the upper A-arms in towards the center of the car.

The frame is fully welded and gusseted at stress points with additional bracing in the upright section behind the seat. A X brace is in the main hoop and connects to the frame members.

The dual pin brakes with a spacer and endurance pads proved to be too expensive to run, due to lack of availability of the thicker pads. Regular dual pin calipers ('65-'66 design with insulators) were added and spacers made (washers) to re-establish the proper alignment of the caliper to the rotor. Three inch ducts were routed to the center of the rotors from behind by running from scoops next to the radiator in the grill over the upper A-arms to the brakes.

Various brake fluids have been used. Currently, Motul seems to give the best performance. Wilwood 780 Degree racing fluid gave very poor performance in '92 and is supposedly pulled from sales. Also Ktech Brake Pistons are now being used and will be reported on as we have results.

Bilstein shocks are at each corner, to keep the springs under control. Currently, a 410 lb fiberglass rear spring holds the rear up. The ride height is adjusted so the rear haft shafts are straight across and parallel to the ground. The possibility of raising the differential upward so the ride can be lowered is being investigated.

Engine And Drivetrain:

Engines have been rather simply prepared. Basic care has been taken and clearances run loose. Most are only standard hot-rod rebuilds with standard aftermarket items, nothing exotic. The 402 big block had a mild cam and was build for torque, rather than high rpm use. This meant that rear ends of 3.08 and 3.55 worked well behind it with a 2.54 first gear Borg Warner T10. The 3.70 rear gave good power out of the corners but was too limited on long straights and was not used after one event. the 402 ran a standard oval port manifold with a Quadrajet mount and a 850 Holley Spreadbore sat on top. the heads were standard oval port heads and offered good low to mid range power.

The 427 L88 produced little power until over 3000 rpm, so the 3.08 gear was a severe handicap in the paddock and on take off from the pits. It was the only gear that could be used for Daytona, where at 180 mph the engine has to turn around 7000 rpm. The L88 was the first fully prepped engine. The heads were ported and chambers matched. The block was standard bore and used 12.5:1 pistons with high domes. Rods were lightened and polished. The cam was stock L88. Lifters were solid. The intake was a factory L88. The aluminum heads were 1969 open chamber, much better breathing than the more desirable closed chamber 1967 heads.

A 327 with mild 11:1 pistons and mild ported heads was used with a 3.70 and 4.11 rears. The 327 was basically similar to a stock Corvette 327 with solid lifter cam and single 650 Holley on an LT1 intake.

Due to rule changes, the 5.0 liter limit was again in force for ASR. A 302 was built on a small journal block and steel 3.0 inch crank. Heads were ported 461s with 2.02 valves and a 780 Holley with a Holley single plane manifold. The cam was a dual profile design solid lifter. Pistons were forged 12.5 TRW. The block was deburred and cleaned thoroughly and had oil restrictors added. Clearances were run at .004" on the mains and a high volume pump installed which supplied 85 psi cold and 65 psi hot.

When the 302 dropped a valve and split the #8 cylinder, we needed an engine under 5 liter in a hurry and took whatever we could find. We had a 307 that was rebuilt by destroking the crank to be under 305 cid. This of course would be a problem since 307 were not performance engines and thus finding pistons extremely hard or expensive.

The pistons of a 283 are only a slight bit too tall so flat top 283 pistons were ordered and the necessary amount cut off the top. This also lightens the piston. Since modern designs tend to avoid domes as they disturb the flame travel, the chamber space was controlled strictly by head size to keep compression up.

The clutch and flywheel were initially the 12 inch lightweight 12 lb. Chevy L88 flywheel and single disk clutch. This worked fine until the 427 was installed and the disk was shredded. A triple disk racing clutch was installed and solved the clutch problems. It has no shock springs on the hubs and is more of an on-off switch than the typical clutch. This is not a street item and should not be used as one. This all lives inside a Lakewood Scattershield.

Headers out the side and into 4 inch tubes get the exhaust away. The tubes carry some mufflers to keep the noise down. Previously, they were 111 dB without baffles, 104 with baffles, and 95 dB with mufflers. A loss of power is not really noticed even though there must be some. However, it is nice to be able to hear at the end of the day. Also, sound control rules are tightening up everywhere in the country, with some tracks now down to 90 dB maximums. Currently, most tracks still run 100 dB to 108 dB maximums, but SCCA will be lowering the maximum at any track to 103 dB soon.

Transmissions have been an assortment of Borg Warner T10D, Borg Warner Super T10, Muncie close ratio (2.43) and Muncie wide ratio (2.54). A standard small Corvette driveshaft is used without any signs of failure. A 350/400 split size u-joint is used to adapt to the large yoke of the Super T10 to the standard driveshaft and has performed well without need for replacement.

Only one rear end failure has occurred. The 3.70 rear lost a side yoke with it twisted off in the splines. Fortunately, this did not destroy any other parts and only required the disassembly, cleaning, and reassembly with a new yoke. The failure was attributed to the L88.

Rear axles ratios have been 3.08, 3.55, 3.70, and 4.11, depending on the track. The 3.08 is a necessity for the engine must run 6000 - 7000 rpm to give speeds of 160 - 180 mph with the 3.08 and these speeds are necessary to qualify for the field at Daytona.

The 3.55 and 3.70 have been run with some engines at Sebring and the 4.11 was needed with the 302. Sebring has many very tight corners that you need to shift down through several gears to get out of and the lower ratios help. Moroso has two very long straights and moderate corners so the ratio was kept higher. The 3.08 has even seen service due to the 160 mph passes down the two long straights.

In 1990, the Corvette ran at Watkins Glen, Summit Point, and Bridgehampton. At this time, the 402 was installed and the 3.70 was in for Watkins Glens, which proved to be too low for the speed there. I suffered through the weekend as changing it was too much chore without a crew. The 3.08 would have worked better (as it was the only other choice then - no 3.55 or 4.11), and it also worked well at Summit Point and Bridgehampton, since I could go low enough with the wide ratio 4 speed to get out of the corners. Had the 402 been an engine which ran at 6500 rpm or a small block, the 3.55 or 3.70 would have been fine.