Leak testing with gas ports

[btnhra]

I have run gapless rings for years. On my new engine I have 043 gas ported pistons. What leakage numbers should I expect on a 4.600 bore? Should the test be done at a high air pressure?

[engineguyBill]

Gas ports won't affect your leakdown results. Perform the leakdown test the same way that you did it with the gapless rings.

[fdicrasto]

2-3% would be excellent with standard style(non-gapless) rings. You can run higher leak down percentages but why not shoot for low #'s

[MadBill]

Your post is a bit ambiguous; it's not clear if your new rings are still Gapless®. If so, I used my Snap On gauge last week on a 5 year old (seats refreshed last winter) 380" 4.175" bore 700 HP @ 8,000 SBF racer with lateral gas-ported 1 mm Gapless® top rings. New it showed zero to 1%. It now measures mostly 1%, the worst 2%. Proportionally for a 4.6" bore, that would be 1.1 to 2.2%.