Aluminum Block - All-Alloy Indian

Sometimes you just have to go all out. Ken Crocie of H-O Racing has been building big-block Pontiac engines for close to 40 years, most of which have been aimed at the street, as is this engine. While front-end weight is a concern in drag racing, it's much more critical when turning corners. Today, the most popular ploy when building a road car is to use an enhanced, all-aluminum LS engine. Crocie's customer wanted to keep his '78 Trans Am purely Pontiac by building a big--no, make that very big--all-aluminum Pontiac engine. Big in this case refers to a 4.50-inch stroke and 4.35-inch bore motor that displaces a whacking 535 inches. But even more comforting than the displacement is the distinct lack of cast iron. This rascal is pure aluminum. Frankly, if an aluminum crank could survive the rigors of 690 lb-ft of twist and 6,000 rpm, Crocie would have bolted one in. Virtually everything else that found its way into or onto this big Indian is aluminum--right down to the connecting rods, rocker arms, and even the carburetor. The payoff to all this alloy happened once Crocie put the engine on the scale. In fact, they had to calibrate it to double check the numbers, as its bantam weight of 415 pounds with a carburetor and a Powermaster starter motor seemed unbelievably light.

So what does it take to build an all-aluminum, big-inch Pontiac engine? Crocie documented the buildup with more than 250 photos we've condensed down to a manageable number to tell the story. When building a custom engine like this, it's not as easy as just bolting all the parts together. What's a little scary is whittling away on a $4,500 block to make everything fit.

The Short-Block

Ensuring all the parts play well with each other is also a major concern with an engine like this. Crocie had to notch the cylinder liners at the bottom to clear the connecting rods, drill coolant passage holes in the block deck surface, and clearance the block in several places to be able to spin that long-stroke Scat crank without interference. In addition to the Ross pistons, he also added a 1/16-, 1/16-, 3/16-inch ring set from Total Seal using a standard-tension oil ring set, since this motor will see plenty of track time.

Top-End Tricks

Cam Specs

Dyno Day

Right: This large-by-huge alloy Pontiac appears to be benign, but nearly 700 lb-ft of torque will be plenty to move that big ’78 Firebird. This photo shows the testing of the Dominator carb and single-plane intake (Test 2), which actually made less torque and horsepower than the Torker II!

Right: This large-by-huge alloy Pontiac appears to be benign, but nearly 700 lb-ft of torq

In Crocie's case, the goal wasn't as much a hero horsepower number as it was a huge payoff in torque. The engine's large displacement promised massive torque potential, and it did not disappoint. When your pump-gas street engine can churn and burn to the tune of 690 lb-ft of torque at a tractor-like 4,400 rpm, the biggest question becomes one of whether the tires will grip. Horsepower was a winning effort, with a max power of 652 hp at a very manageable 5,400 rpm. Long-arm engines can really tax those pistons if you spin them up too high, but with this beast there's little reason to spin it beyond 5,800 rpm. We dialed in a 3,300-pound car, a manual trans, and 3.42:1 gears into the Quarter Jr. dragstrip simulation program, which estimated 10-flat at 136 mph. Sweet! Just thinking about how this big motor would push us back in the seat at 60 mph in high gear is tantalizing. Where do we sign up for a quick lap?

The Quick Fuel 850 carburetor was more than enough to feed 650 hp.

Dyno Testing

By Jeff Smith

Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!