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IHRA Chevy Big Block - From Street To Strip

Prepping The ZZ 502 Crate Motor For IHRA Top Stock Competition

By Barry Kluczyk

Consider this: For three seasons of knock-down, drag-out competition in IHRA's fiercely contested Stock ranks, the big-block in Monty Bogan, Jr.'s bright-yellow '69 Camaro routinely screamed to almost 7,000 rpm between gears and generated enough torque to yank the front tires off the ground on almost every pass.

In those three seasons, however, Bogan never had to crack open the engine. No valve adjustments. No bent valves. No spun bearings. Nothing.

Oh yeah, and each of those wheels-up, 7,000-rpm passes was made with less than 2.5 quarts of oil in the motor. You read right. Bogan ran the engine for three seasons with the dipstick barely getting wet. In fact, most passes would see the oil light start to flicker just as the car crossed the traps. To anyone other than a dyed-in-the-wool Stock competitor, this sounds like a nutty way to treat a high-dollar race engine. But, such is the nature of this competitive class of drag racing, where finding the slightest performance edge within the rules-in this case, reducing crankcase windage-has become equal parts science and art.

In addition to standard Stock class competition, Bogan is also a key competitor in the growing Top Stock field. Top Stock pits mostly classic musclecars against one another on a Pro Tree. Although a weight break is given to small-block-powered cars, most Top Stockers run a big-block to push the heavier, less aerodynamic '60s iron through the air in about 10 seconds on 10.5-inch tires.

The rules of Top Stock allow many types of cars to compete, but the engines in them must be based on readily available crate engine packages from the original manufacturer-an engine designated by the manufacturer and approved by IHRA. For GM Top Stockers, the ZZ 502/502 crate engine is the accepted big-block.

With the competition in Top Stock really heating up, Bogan felt it was time to give his never-been-touched engine a much-deserved rest and drop in a fresh, more competitive combination. With some advice and guidance from GM Performance Parts-where the crate motor was coming from in the first place-Bogan enlisted the service of McLaren Engines (a division of McLaren Performance Technologies in Livonia, Michigan) to build the rules-complying crate motor. We followed along as McLaren's Curtis Halvorson completed the assembly, then tuned the engine on one of the company's dynamometers.

Halvorson has years of experience building racing engines-everything from bracket cars to supercharged monster truck motors. His insights during the Top Stock engine build-up revealed two things: First, it doesn't take exotic, unobtainable parts to build a reliable, consistent, and powerful race engine. Second, what works on the track isn't necessarily what you want for a street engine.

To stay within the rules there are things that can't change, such as crankshaft stroke. But, within those guidelines, there are ways to build the engine for the track that will increase horsepower. The best way is to build to the rules, not over them. In the case of Bogan's engine it works; compare the factory-rated 502's output, at 502 hp and 567 lb-ft of torque, to that of the Top Stock version outlined here, which made 657 hp and 598 lb-ft.

By Barry Kluczyk
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