Leak down on Cylinders

Hey guys...what kind of leak down numbers are you getting when checking cold. We started our motor a couple times before christmas...and we have the motor out doing some cosmetic work on the body. Checked the cylinders...most were around 20-22%. Not sure if that's normal leak cold?

Combo is 526kb hemi, dykes top ring...gap is .022-.024". Not running any gapless total seals.

Josh

 

tight gap!!!!..Dave

 

Tight? Really?? We were thinking it was a little loose?

 

The leak down sounds fine. Myself, I would gap the top ring at 32.

 

That is REALLY tight!

 

You know...i might have to ck my notes...maybe i meant 32-34?

 

Ken you can file my rings..we always gap at 32 to 34 depends on several things..we also use a Goodson power ring filer..this is one of the best tool you can get yourself we can do a full set in less than 10 min.Dave

 

Ora always told me not to worry about leak down only if you start to run bad then look at in till then don't..Dave

 

I agree. I like my leak downs to be 20 or so in the shop, but if we're at the track, I only get really concerned if the leak down is over 50% and I can hear it coming out of the intake valve. If the exhaust valve is leaking, it usually cleans up the next time you fire it, unless the head is about to fall off

 

The only thing I use leakdown for is a comparison to the rest of the cylinders. Not a condition of the motor itself. If you have 20% leakage, I would say that's good, as long as the rest of them are comparable. Gapless rings create their own set of issues. Besides, you don't race with the engine not running. And I guarantee, the rings will seal better with cylinder pressure. Gapless rings have a tendancy of trapping blowby between the top and second ring. When this happens, it unseats the top ring (bad) and you lose ring seal and power. But the leakdown number look great, who cares.

 

Forgot something. One time I was told to try something, so I did. I did a compression test with our standard ringset, hellfire dykes top, cast 2nd and 3 piece oil ring. All the plugs out, throttle wide open, gauge read about 200PSI after the 4th pump. Pulled no. 1 piston out, changed the 2nd ring to a gapless ring and put it back together. No other changes, everything was the same. After the 4th pump on the gauge, 145PSI. After advancing the cam a total of 6 degrees, I finally reached 160PSI. I know what your thinking, yes, the ring was put together the right way, it wasn't upside down. Went back to the cast 2nd ring and ran the compression test again. It escapes me now what the gauge read with the cam advanced, but after putting the cam back to where it was, it read 200PSI again. After that, I threw all the gapless rings we had in the shop into the trash.