Building A C3 Corvette To Handle Power

Alan’s ’Vette

Alan’s ’Vette

An enthusiast’s journey at making a shark his own

Story Jim Moore Images Alan Rothman

We’ve all heard it said that we really don’t own our Corvettes and muscle cars and that we’re actually just the caretakers until they are passed on to the next wide-eyed and excited enthusiast.

But while we’re obligated to respect the history of the past, we really owe it to ourselves to make a few memories and create a little excitement of our own.

People handle this in different ways. Some seek to preserve the very essence of how it came to them, which means they are often relegated to spending more time in admiration of their prize than driving it. After all, driving induces wear and it’s only original once. Others come to us as projects, victims of the exuberance of their prior owners who either lacked the taste, talent, dollars, time, patience or restraint to keep their new toy intact. When this happens, you can either try to restore it back to its original glory, or maybe add a few custom touches of your own with more power, comforts or better handling. But when they come to you in pretty nice condition, you’re torn between making it perfect or going a little crazy with it.

Alan Rothman found himself right in the middle of this latter predicament when he brought this ’71 Brands Hatch Green 350/270 coupe home. But let’s back up a few years. In the fall of 1971, Stephen Kimzey, a young NASA physiologist in Houston, went shopping with his wife Ann to replace her ’66 Impala. With his sights set on a Corvette just like all of his astronaut buddies were driving, a deal was struck for this ‘71 at the Chevrolet dealership of long-time family friend, A.J. Foyt. It had all the options they wanted without the add-on fluff that would drive the price out of reach for the young couple.

For the next 17 years, the Corvette served commuter duty for whoever got to the garage with the keys first. In the ’80s it strutted in parades and along Seawall Blvd. at Galveston Beach as well as being a regular feature at daughter Stephanie’s high school parking lot. But when she left for college, it was decided to not take the “old car” away from home for reliability reasons and it was left parked most of the time. In 1979 Stephen passed away at the early age of 39, and by 1988 Ann decided it was finally time to part company with the family ’Vette.

After slipping through a couple of owners, in stepped Alan. There had been a nice repaint along the way and the old 350 still ran well. With the purchase came all the original paperwork including the “Corvette Owner’s Card” issued to Stephen, as well as complete service records for every item that was ever touched over the years. But right here’s where you have to understand that Alan is no stranger to speed. He’s had a nitroused 10-second Trans Am and rides a street-legal turbocharged Suzuki Hayabusa bullet to 8.68 seconds at 168 mph times in the quarter mile (as well as 225.906 mph wide open at the Texas Mile on mild boost settings).

With the Corvette though, he really liked the way it looked and didn’t want to mess up what the General had provided. But, it just had to get a whole lot faster than the 15.10 e.t.s shown during its one and only track outing! The first plan was to build a big-inch small block with all the good parts to make it survive huge horsepower. After shopping various engine builders, sticker shock, similar to what the Kimzeys must have encountered, smacked him hard when he realized it was going to cost more than twice the car’s original 1971 purchase price to build it!

A new direction was forged when he discovered a well-respected builder in Colorado who was putting together some of the most cost-effective stroker big blocks on the planet. Going through the available combinations, Alan worked closely with Mark Jones at Vortec Pro Engines to create a pump gas 496 with proven horsepower that could handle air conditioning, power steering, power brakes, an automatic transmission and, oh yeah, a promise that it would run 10 second e.t.s using 3.08 rear gears and no power adders!

Now everyone claims their engine was tested on a dyno, right? The truth is that the dyno is a tuning/testing tool and the numbers don’t mean anything unless they translate to real in-the-car performance. Mark Jones has been developing his combos for years and has no qualms about putting them to anyone’s test. More than once he’s been called out concerning the seemingly high correction factors that are necessary when testing at Colorado Springs’ 6,200-foot altitude. But Mark stays in close contact with Harold Bettes (who you may recall from SuperFlow dyno fame) who actually came to verify the calibration of the dyno before Alan’s engine was tested and to witness the pulls!

After doing his homework on Mark’s abilities, Alan was confident that the corrected 662hp/675 lbs-ft torque numbers produced by his engine in Colorado were real. But his buddies back near sea level in Houston saw a golden opportunity to have some fun and answer the whole correction factor question one way or the other. A pool of money was assembled to finance another test session and when the new 496 arrived, it went straight from the crate to a SuperFlow 902 dyno (Mark uses a 901) housed at the Owens Racing Engines shop. The group had consistently seen the numbers from this dyno measure up on the track over the years and knew that if Alan’s new toy could make the grade here, there would be nothing left to do than make it hook up and go down the track! To duplicate the tests exactly as in Colorado, EVERYTHING was verified from the ignition timing to the valve cover breathers and even down to the exact amount of oil in the pan! Guess what? After riding 1,000 miles, dropping over 6,000 feet in altitude and being tested on a completely different dyno, this low-budget monster cranked out 657 horsepower and 662 lbs-ft. So much for correction factor issues!

Now it was all back in Alan’s hands as he went to work making the small block to big block conversion (saving all the original parts, of course) by using GM bracketry to maintain his stock P/S, but at the same time updating some items. Alan installed a Vintage Air A/C system that blows 38-degree air even in hot and muggy Houston. A complete three-inch stainless crosspipe exhaust was built by Rick’s Lonestar Muffler and attached to a set of Jet-Hot coated Hooker 17/8-inch headers. The original TH400 trans was freshened by Mike at Michael’s All Transmission and a tight 10-inch converter was added to keep the street manners nice while still providing a decent launch. The governor has been tuned to provide full throttle automatic upshifts at 6,000 rpm.

Initial shakedown cruises revealed that while the stock cooling system was adequate, it left precious little margin for long highway cruises with the A/C operating. This put Alan on a long series of tests of various fan and radiator combinations to create super cooling while keeping power losses to a minimum. The final version is a Lincoln Mark VIII electric fan pulling through a DeWitts Direct Fit aluminum radiator.

Once everything was operating perfectly, Alan again hit the dyno, but this time he was looking for rear wheel horsepower to see what he really had at the end of the independent rear suspension differential. This would prove to be interesting, given the parasitic drag that a fully-loaded Corvette with an automatic transmission creates. The tests involved various fans, carb spacers, air filters, etc. and offered sobering insight into reality while knocking out another few myths. For instance, when the period correct and ultra-cool L-88 screen assembly was added to the top of the L-88 filter base, 7 hp disappeared! With no air filter assembly at all, simply shutting the hood created enough turbulence to knock off another 30 hp. A viscous-type mechanical fan made 15 more of them go hide. And on and on it went. The end results on the Dynojet were 424.4 hp in pure off the street trim and 460.2 hp in “race mode” with the mechanical fan removed, the hood cracked open, a one-inch carb spacer and just the L-88 filter base in place left to shove the 3,730 pound (with driver) cruiser down the quarter mile.

Next stop: Houston Raceway Park on test-and-tune night. Right off the highway with the original 3.08 rear gears driving M/T 255/60R15 drag radials on a full set of original eight-inch Rally wheels, Alan dropped a few jaws when the scoreboard lit up with a 10.99 at 123.88 mph pass! How’s that for a sleeper? The Vortec Pro 496 had lived up to its most important promise — a 10 second timeslip — and earned Alan an invitation to go home due to no roll bar! With that milestone accomplished, Alan knew there were only a few more nights at the dragstrip before he would end up riding home on a flatbed with a pile of broken Corvette IRS parts. Built for handling with the engines and tires of the day, the stock 10-bolt IRS was now being pushed to its limits.

In stepped Mike Dyer with one of his killer Super 10 rear axle packages that shoves the reliability bar way up. Mike begins with a hand-selected housing and posi case that he spends hours machining, detailing and polishing to accept heavy-duty spider gears and a larger cross shaft from a 12-bolt differential. He then eliminates the OEM’s internal Positraction clutch spring arrangement by adding the shims necessary to tune the assembly to his specs as well as adding massive steel billet main caps. The rear was completed with a set of Tom’s Differentials 30-spline inner axles that drive three-inch by .095-inch wall half-shafts attached to Tom’s 31-spline outer stub axles. During the rebuild, Alan worked his calculator hard to determine that a move to 3.36 gears would help acceleration a little and still be highway friendly.

With the newfound confidence that the stronger pieces brought, Alan hit the track again to produce a 10.77 at 126.08 mph right off the street. Later, on a chilly 41 degree February night, a test was made with some skinnier and lighter front tires along with a few other minor tricks. The cool air was great for the top end charge, but a new weather-induced carb stumble and a trans that decided to begin shifting slightly weird hurt things a bit. Still, the time slip read a new best 10.70 at 127.99 pass! Since the no rollbar discussion is pretty common, Alan’s test-and-tune nights are usually limited to a few 1/8-mile passes and then one Banzai hero run. The usual 1/8-mile timeslip reads real close to its best 6.75 at 103.88 with a 1.53 60-foot time. As you can imagine, it takes a while to really dial in a car at the track that way. But with a lot of planning and research, Alan has proven that you can assemble it right the first time and hit pretty close to your target right from the start. Mark and Alan believe there is a 10.50 at 130 mph still to be had with further tuning.

We can easily imagine the gleam that an earthbound rocketship like this would bring to a young NASA employee, and maybe, just maybe, some of Stephen’s DNA still lingers within the fiberglass and steel of Alan’s Corvette. Who knows? But certainly Alan has found the perfect balance of paying homage to the past while creating a legion of prospective new owners each time they see him lift the wheels off the line and then casually flip on the A/C to make the long drive home.

When the time comes for Alan to pass this legacy on, there will no doubt be plenty of folks ready to step up for their chance to live the Corvette dream. But I bet this one won’t be left to garage duty and parking lot shine-’em-up detail. This Corvette has been bringing smiles to faces ever since each member of the Kimzey family took their first drive, and it wouldn’t be right to let that feeling ever end. Alan sure hasn't!