When Chevrolet announced it was replacing its W-series engines with the 396ci Mark IV big-block, Southern California drag racer Tom Sturm was among the first to order one. It took a while for Chevrolet to fill the order; so long, in fact, that Sturm wound up buying a 396 from his local dealer—and the ’65 Impala it came in.
Sturm went through the engine top to bottom, and also modified a ’64 Malibu that would be its eventual home. Car Craft magazine covered both the engine and the car in its September 1965 issue in stories written by the magazine’s Technical Editor, Bud Lang.
Lang described the engine rebuild in granular detail. Among the highlights: The block was bored to 4.25 inches and the crank stroked to 4.00, bringing its displacement to 454 ci. Sturm had the connecting rods magnafluxed (several times), the big ends resized, and the small ends bored and bushed. The tops of the Ansen forged aluminum pistons were machined to fit the 116cc combustion chambers that had been polished by Joe Mondello, resulting in a compression ratio of 12.4:1. The Sig Erson 990 BH cam Sturm chose “bumps the valves a full .565-inch,” wrote Lang, requiring reliefs be cut into each cylinder.
Sturm ran some initial tests on the engine using its stock carburetor and intake manifold, but swapped them for a Man-A-Fre carburetor-injection system once the company had developed its unique induction for the Mark IV. “The low aluminum carburetor ‘plate’ positions four big Pontiac carburetors, totaling more than 19 square inches of throttle bore, directly atop the intake ports, thereby affording the shortest route possible for the fuel and air mixture to reach the valves,” Lang wrote. The engine got additional fuel as needed at high rpm from injector nozzles at each port. Unfortunately, Sturm was still sorting out the induction system when the story went to press, so Lang had no performance data. “Early tests have proven that the greatly increased throttle bore and venturi area available with the Man-A-Fre have been beneficial.”
Meanwhile, the Chevelle was stripped “to a bare body and frame,” and Sturm replaced the hood, front fenders, front bumper, doors, and trunk lid with fiberglass parts. “Also the whole body was moved rearward a few inches to alter the weight distribution,” Lang wrote. “Normally racers tend to shift both axle assemblies forward a specified amount, but Sturm figured it was easier to shift the body rearward.”
To handle the big-block’s torque, Sturm swapped in a ’57 Pontiac rearend (with 4.88s) and attached 2x4-inch rectangular traction bars between the housing and brackets at the car’s midpoint. Air Lift coils and bags suspended the beefy axle. Up front, Sturm mounted the complete straight-axle/leaf-spring assembly from a ’39 Willys to a new front subframe. The stock Pontiac drum brakes were left in place in back; Airheart-Cragar discs were used in front.
When it came time to install the engine, Sturm hooked it to a Muncie four-speed via a Hays steel flywheel and 10 1/2-inch clutch. “Sturm figured on putting quite a few more ponies through it and under anything but normal operating conditions,” Lang wrote. “Therefore he went to the beefed Hays units which also offer improved lining material.”
Prior to the 396’s installation, though, Sturm tested the altered Chevelle using a 409 he borrowed from friend Tom Jacobson’s AA/S ’62 Chevy. At Lions “the Chevelle got to the lights six miles per hour faster and a full second quicker than did the engine’s former mount,” Lang reported, “so Sturm was quite confident the 396 pumped up to 454 inches would do a commendable job when ready.”
Did it ever. Sturm raced the car all over the country, running in the 9s at 140 mph, according to Bob McClurg’s book Diggers, Funnies, Gassers & Altereds.