Ever since Total Seal’s mainstream release of the gas-ported piston ring, there has been a question on everyone’s collective mind: “Which performs better, a gas-ported piston with traditional rings, or a traditional piston with gas-ported rings?” Well, we’re about to find out.
Originally created to skirt competition rules which barred the gas porting of pistons themselves, gas-ported piston rings have come into the light of the mainstream engine rebuild recently. Obviously, trickle-down technology from motorsports is nothing new, but the question remains, which is the more effective solution for someone not building an engine to a rulebook?
Well, When you take Lake Speed, Jr. — a man driven by data and testing — and ask him the question, he’s not afraid to head to the dyno and make a video. For this test, Speed headed to Shaver Specialty Racing Engines to conduct a comprehensive test in order to provide real-world data to answer the question.
The test was performed on a 9.5:1-compression, 383 cubic-inch small-block Chevy, which is currently set up with a set of lateral-gas-port pistons and standard, non-ported piston rings. Set up on the dyno, the engine made a 3,000-6,000 rpm test sweep, with a peak horsepower of 451.7 horsepower. With the baseline established, the engine was torn down, a fresh hone applied, reassembled with the new configuration, and broken in exactly as it was with the baseline. The new hone is only taking about .0001-inch of material off of the cylinder wall — just enough to get the correct surface finish.
The second configuration consisted of a set of traditional, non-gas-ported pistons set up with Total Seal’s gas-ported piston rings. The setup was as identical as it could be made, save for the top ring. The fueling and timing were identical, and the same 3,000-6,000 rpm sweep was performed. This time, the dyno showed a peak horsepower reading almost five horsepower higher than before, with 456.3 horsepower.
For the third test, they used the same piston as the previous test, but this time, a standard, non-gas-ported top-ring assembly. With all the other variables identical, the numbers on the completely unported configuration dropped (as expected), with a peak power of only 449.3 horsepower showing on Shaver’s dyno screen.
Besides the power differences, engine blow-by was measured on all three runs using an analog blow-by gauge as well as a crankcase pressure sensor, and the data was extremely clear. At the start of the pull, the non-ported combination started at about 0.875 inches of Mercury crankcase pressure, the ported piston was right at 0.5 inHg of pressure, and the gas-ported rings were the closest to atmospheric with 0.11 inHg of crankcase pressure displayed.
Where the real difference is, was at peak RPM. While both ported combinations more or less held their ground throughout the pull, the non-ported combination slowly climbed from 3,000 to 5,000 rpm and then spiked hard to 2.2 inches of Mercury from 5,000 to 6,000 rpm. Those pressures correspond to 10cfm of blowby for the non-ported rings, and 3cfm of blowby for the ported-ring setup. Speed attributes the elevated numbers to ring destabilization at the elevated RPM because of a combination of increased inertial loads and the associated cylinder pressure drop not stabilizing them.
While this is a single test, Speed says that the results are typical for all of their customers who have done similar testing of their own, especially the blow-by numbers. “We’ve seen nearly identical blow-by results in two other engines,” says Speed. Whether you’re rebuilding an old engine or putting together a new high-performance mill, these new gas-ported piston rings are worth a look.