LS Engine Build - Dyno Testing - Car Craft Magazine

To finish out the dyno installation, we had to add an external oil filter to the Moroso oil pan, bolt on the Kooks 1 7/8-inch headers, and plumb the exhaust with a pair of Borla 3-inch stainless mufflers. The last step was to add the Quaker State Q synthetic 5W-30 oil.

To finish out the dyno installation, we had to add an external oil filter to the Moroso oi

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.

We started testing with a 750 HP Holley carb but discovered this engine really likes a larger carb. All our testing was with this Holley 950 HP carb, but since we only saw single-digit power increases, we probably could have made the same power with an 830-cfm carb and the Wilson tapered spacer.
We started testing with a 750 HP Holley carb but discovered this engine really likes a lar
All the factory late-model heads use 0.750-inch thread reach plugs with tapered seats instead of the more popular gasket-style plugs. These are Autolite AR474 race plugs.
All the factory late-model heads use 0.750-inch thread reach plugs with tapered seats inst
If you are converting from cathedral-port heads to L92s, remember you will need all new rockers and support rails. The L92 intake rocker (left) is offset to accommodate the larger intake valve, and the L92 exhaust rocker is also different from cathedral-port heads. The rocker ratio remains the same, however, at 1.7:1.
If you are converting from cathedral-port heads to L92s, remember you will need all new ro

After baseline-testing the L92 heads, we tried the slightly larger Comp cam and saw a minor power gain. After-testing analysis revealed that more exhaust duration would help make more power when using these large-port heads.
After baseline-testing the L92 heads, we tried the slightly larger Comp cam and saw a mino
Next we bolted on the GM Performance Parts GNC-ported L92 heads, retaining the factory-supplied valvesprings, which worked well.
Next we bolted on the GM Performance Parts GNC-ported L92 heads, retaining the factory-sup
One trick we learned from dyno operator Ed Taylor is to not plug the heater hose connections, since this affects proper coolant flow. If you don't plan to use a heater, create a loop between the heater hone connections. Another tip is to use ARP stainless metric studs (PN 400-8034) instead of header bolts. The header installs easier and there's less risk of tearing up the threads in the aluminum head.
One trick we learned from dyno operator Ed Taylor is to not plug the heater hose connectio