In Part 1, our lengthy 30-year plan on how to rebuild our tired 1962 Corvette fuel-injected 327 was finally put into motion. In short, while rebuilding the short-block and heads, we didn't overlook anything. We chose to lower the compression ratio to 9.9:1 (measured) with Speed-Pro's hypereutectic pistons and a 0.030-inch deck height. Valley Head Service installed hardened exhaust valve seats so the engine would run on today's 91 octane pump gas with no problems.
Valley Head Service also completely rebuilt the rare 461-X, 1.94- inch, big-port heads, and then Joe Sherman Racing Engines cleaned up the head ports and each port's short side radius. An additional 20-cfm air- flow was realized, from which Joe estimated we'd see an additional 20- 30 hp. We also installed the mildest of the three hot, new Comp Cams "Thumper" hydraulic roller camshafts (#12-600-8) along with its new "Beehive" valvesprings (with much smaller retainers).
We shelved the 650-cfm Rochester fuel injection (which virtually none of you have) in favor of a tried-and-true Edelbrock 750- cfm AFB carburetor (#1407) and Performer RPM intake manifold (#7101). The camshaft and kit, carburetor and intake manifold are all readily available.
The short-block (less camshaft) was balanced at Valley Head Service and blueprinted at Joe Sherman Racing Engines. The oil pump is a genuine stock original. Why? The '62 Corvette's factory gauge registers 0-60 psi. Any high-volume or highpressure pump will exceed this maximum, thus burying the needle and making it unreadable.
While rebuilding this engine, we knew a 1962 Corvette's powerlimiting factor on the street is the 2.25-inch main exhaust pipe diameter and its even smaller diameter tailpipes. The car's "X" frame has oblong holes where the exhaust pipes pass through. Because a 2.5-inch diameter pipe will rattle against the frame, guys decades ago used to torch/grind the frame holes larger. We do not wish to do this. Knowing that '62 street Vettes ran in the low 13s with slicks is fine with us today.
We were mainly concerned with the rebuilt 327's maximum horsepower and its mid-range torque output. Torque is what makes a car accelerate up to maximum rpm through the gears. For a street machine to run its very best, it either needs high numerical gearing or maximum torque production. For a best-running, all-around engine, torque is what matters most-even in a little 1962 331ci (327 + 0.030-inch overbore), 9.9:1 compression, Corvette engine.
More On Comp Cams' "Thumper"Why use a hydraulic roller camshaft? For race engines and street engines, a roller cam is the best there is. Back 45 years ago, in 1963, I was running my dad's 1961 Corvette with a '63 F.I. 327 long-block and twin WCFB carbs in CM/SP class. A chance to buy a Racer Brown R39 roller cam came up and I jumped on it. The car ultimately went three-tenths quicker and 4 mph faster compared to the Duntov camshaft. Power output was now pretty much limited to how much gas the mechanical fuel pump could provide. Mid-12s at 108 mph was about it. This '61 went undefeated due in toto to its potent roller camshaft. There is certainly nothing wrong with a hydraulic or solid lifter flat-tappet camshaft for your street engine. Comp Cams has 'em all. But this particular Thumper cam offers, in my opinion, a lot more part-throttle driveability and fullthrottle power. It's like having your cake and eating it too. It costs more, but it is worth it.
I initially hoped the 331's horsepower level would be 360. Joe Sherman thought 400. We were both wrong. Try 409 at 5,800 rpm and 416 at 6,100 rpm. That's 101 ponies more than factory fuelie provided, for those of you keeping score at home. Sherman feels a street engine should never have to rev over 6,000-6,200 rpm, more or less. This was certainly a performance eye-opener.
So was the engine's torque output. It produced 390 to 400 lb-ft from 3,500 to 6,000 rpm (and probably more under 3,500 rpm). The small diameter main exhaust pipes from our Hedman headers to the mufflers and smaller tailpipes may kill off 10 to 15 hp due to increased backpressure, so I imagine we will fabricate some custom tailpipes.
We didn't rebuild this original engine to drag race, per-se. We've owned this piece of real estate since 1970 and plan to cruise around in Southern California and Nevada. We do plan to reinstall the Rochester Ramjet fuel injection-strictly for comparison's sake. We have a G-Tech Pro SS electronic accelerometer and will compare the 750-cfm Edelbrock induction to the 650-cfm constant flow port injection after the car is running.
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