Diceco thanks for the link. On the prop issue i guess thats why is so important to have a test standard prop that is tha same manufacturer dia and pitch for all our test information.

Aviator I cannot disagree with any of that and I think i have been underplaying the importance of a good seal. I think on my engine that when it warms up it is losing seal for whatever reason. when run to full throttle it runs out good then slowly losses about 180-200 rpm as it gets hotter. if reduced to idle then let cool for a bit and run back up to full throttle it has the same results. This is part of why its so hard to get a good consistent reading and why i say my testing is somewhat flawed.

I made a leakdown tester yesterday. I could not air it up to 100 psi as my buddies shop i made it at didnt have air that went that high. he best i could do is 80 psi.. When I built it i had made a orfice with a .040 dia. when used on my engine with the prop at TDC and held there i got a reading of 78/80 psi. That means the input pressure was 80 psi and the pressure in the cylinder aft of the orfice was 78 psi. this can be expressed as a percentage of leakage but I need to figure out the math. When run at 100 psi the math is easy lol. 1 psi - 1 %.

I didnt think this had a good enough resolution so I wanted a smaller orfice. the best i could do was .023 as I had to use a tip out of a wire feed elder for the orfice. smallest drill bit I had was .040. when this tester was run at 80 psi i got a reading or 76/80. This is a little better resolution. I would really like a .010 orfice. I think even as this dosent seem like much leakage and in a 350 chevy it wouldnt be but on this small of an engine its a bunch. I removed the carb and held the reed valve open when this test was performed as my thought was that if i didnt with the reed valve an leakdown wouldn have a place to go like in a crankcase on a four stroke engine. You could hear quite a bit of leakage. If you rotated the prop the seal was best at the tdc and was pretty lousy at ather spots int he stroke.

I will get some pictures of this on later and will keep working on this so we can get an acceptable range for testing standard purposes. this should help give more consistent information from all of us if.

I would really like to see what kind of a reading av8to1977 is getting on his as his seems to be the best as far as seal improvements so far.