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LS Engine Build - The Garage-Built LS Stroker, Part II

Last Month's Homebuilt 404ci LS Engine Is Now Making Noise Testing Four Different Cylinder Heads On The Garage-Built LS Stroker, Part II

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Dyno Testing
We began testing with the stock 6.0L heads to which we added a set of Comp beehive valvesprings and Comp 0.080-inch-wall Hi-Tech pushrods to ensure the valvetrain would not suffer from separation anxiety. This first test revealed what we gained by just bumping the displacement along with a slightly more aggressive camshaft. Our original 6.0L engine combination with a GM Hot cam made 450 lb-ft at 5,000 rpm and 483 hp. These same stock 6.0L heads surprisingly didn't improve peak horsepower, but the torque jumped 30 lb-ft at the peak, which is what you'd expect from 40 more cubic inches. Next, we bolted on the WCRCH-ported 6.0L heads. This time, we saw a gain in overall power. Torque improved mostly after 4,000 rpm, gaining 19 lb-ft at the peak to a satisfying 505 lb-ft. Now it was time for the big boy heads.

Our first pull on the dyno with the bigger L92 heads fell short of 530 hp. Torque was up, which was encouraging, but the peak horsepower was disappointing. Our first move was to add a Wilson carburetor spacer to see if the power would improve. We gained 3 or 4 horsepower but not nearly enough. Next, we swapped in a Comp cam with more lift but a touch less intake duration. This test, after some tuning, delivered a peak of 550 hp, which was more to our liking, along with a max torque of 516. This also included a Wilson carburetor spacer.

The final test saw the GMPP CNC-ported L92 heads bolted in place. As quickly as the swap was completed, we were back making noise, but since the flow bench numbers revealed that the major flow increases occur above 0.600 inch valve lift on the ported L92 heads, this test didn't promise a huge increase. True to form, we gained 11 hp, bringing the peak horsepower to 561 at 6,400 rpm.

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