Engine Build and Dyno Testing - How to Pass a Lie Detector

We used Cometic multi-layer-steel (MLS) head gaskets for this application. We’ve found that these gaskets offer a better combustion-chamber seal than do composition-style gaskets, crushing evenly when the cylinder head is torqued in place.

In the homestretch now, we drop the Dart Pro 1 CNC heads in place and secure them using an ARP head-stud kit. The all-aluminum engine is looking great, and the ported Darts should help it make big power as well.

We chose Jesel’s shaft-mounted rocker arms for our engine, ensuring the highest possible level of valvetrain stability. Unlike pedestal-mounted rockers, the Jesel rocker pairs are mounted to individual shafts, and don’t move or flex even when utilized in extreme-duty and high-rpm applications.

After setting valve lash and installing our Dart intake, ATI balancer, and valve covers, APE owner Kevin Willis and machinist Scott Bailey placed the engine on the dyno cart and rolled it into the dyno cell. We were eager to hear our 427 run—and optimistic about meeting our goal of out-powering the LS7.

We primed the engine’s oil system, then dropped in our distributor and Live Wires spark-plug wires from Performance Distributors. We also installed a 750-cfm “shop” carburetor for initial break-in, to check for leaks and seat the piston rings. Once the engine was warmed up, we applied a load with the dyno servo, then made one short pull to 5,500 rpm to check for problems. None were found, so we shut things down and drained the break-in oil.

After engine break-in, we always cut open the oil filter to look for contaminants. While it’s common to see a small amount of aluminum, silicone, and/or bearing material in the filter, excessive material could mean trouble. Our filter looked very clean, so we deemed our engine healthy enough for some real dyno pulls.

For our initial dyno pulls, we used a 950-cfm Q-series carburetor from Quickfuel Technologies.

Our 427ci small-block responded nicely, making nearly 520 lb-ft of torque and more than 573 horsepower with 32 degrees of ignition timing. Having already beaten the LS7’s numbers handily, we got to work tuning the engine for optimal power.

We made several dyno pulls with the 950 carb, using oxygen-sensor and exhaust-gas-temperature data to achieve the most favorable mixture, then adjusting ignition timing to optimize power output. Our best pull with the 950 carb came with a 2-inch open spacer, netting 609.6 horses at 6,600 rpm.

Thinking the engine might need more fuel and air, we installed a Quickfuel QFX 4700 1,050-cfm carburetor and retuned the combo for maximum power. With the larger carb, the engine made its best pull of our session, netting 537.7 lb-ft and 613.3 hp. Even better, the torque and power curves were smooth and broad, indicating that this engine will pull strongly throughout the rpm range.

As this dyno sheet indicates, our aluminum small-block topped the LS7 by some 108 hp and nearly 70 lb-ft of torque. Our 427 also makes its peak torque and power at similar rpm levels, making this a valid comparison with the more modern LS engine.

While on the dyno at APE, we made multiple tests that we don’t have the space to cover in this article. In a future issue we’ll outline how cam timing, carb spacers, ignition timing, and valve-lash changes all affected the power output of our LS7-killing small-block. For now, we’re gloating about achieving our goal—and looking forward to meeting a new Z06 at the track!