Leak down oddity

[ealmei]

Has anyone experienced this:
While doing a leak down test if you move the crank slightly the reading gets better, maybe by 5%?

Is one of the valves still slightly open at TDC?
Could I have a dirty valve not closed all the way?
Could the timing be off just slightly?
I am I doing it wrong?

It is a stock engine that has never been molested.

I did the leak down test with two people. I had a rubber hose down the spark plug hole with my fingers right on the valve cover to stabilize the hose and feel the slightest movement up or down of the hose slipping through my fingers. Another person turned the crank to get it at TDC. I was sure that it was on the compression stroke because I blew air until I heard it leaking in the intake.

While putting the tester to the spark plug hole the other person held the crank still so that it didn't move under pressure. Once I got a reading I asked the person to move it slightly one way or another. Sometimes it got worse and other times it got better. But I was always made sure that we started at TDC holding the crank steady.

Any insight is appreciated.
thx

[Fstrnyou]

If you check leakdown at TDC of compression stroke, you can be assured that no valves should be open.

[ealmei]

Originally Posted by Fstrnyou If you check leakdown at TDC of compression stroke, you can be assured that no valves should be open.

Thanks. I'll check it tomorrow.