Are they worth anything? Flathead has ez spin, clones and LO206 have compression releases. Are they really only any good on animals? If so how much can I expect with flatheads and clones. Will an electric starter spin fast enough to deactivate the compression release on clones and LO206?
Compression tests
- Thread starter ChuckZZ
- Start date
Petty Race Engines
Member
And to do a compression test on a OHV engine .. remove the rocker arms
flattop1
Dawg 89
My experience is with the pull start they show around 65 lbs .
If it shows 30 it's bad .
I never used the electric start to check it should show higher .
If you have both do the test , just don't forget to write it down .
That way you won't have to rely on memory .
The leak down is better in it also indicates the area of leakage .
Either is much better then neither .
(With a compression test , having the throttle fully open will provide better data . )
If it shows 30 it's bad .
I never used the electric start to check it should show higher .
If you have both do the test , just don't forget to write it down .
That way you won't have to rely on memory .
The leak down is better in it also indicates the area of leakage .
Either is much better then neither .
(With a compression test , having the throttle fully open will provide better data . )
flattop1
Dawg 89
You can hold it at tdc and pressurize the cylinder .
Then listen for where the air leaks .
You just won't get data .
Unscrew the hose off the compression gauge and pull the valve core out of the bottom .
Don't lose it , mine was a lower pressure then the common ol`tire valve core .
Then listen for where the air leaks .
You just won't get data .
Unscrew the hose off the compression gauge and pull the valve core out of the bottom .
Don't lose it , mine was a lower pressure then the common ol`tire valve core .
Last edited:
alvin l nunley
Site Supporter
You do what you want, but a compression check is real quick and easy and can tell you a lot.
OVALTECH1
Site Supporter
do a compression test on a cold engine that had the oil drain down and then again on an engine at operating temp with oil on the cylinder and rings and tell me how accurate it is. Furthermore do it with the carb butterflies closed then open and tell me there’s no accuracy discrepancies..... I have one and I sometimes will use it... but I prefer a leak down any day of the week.
Freezeman
Site Supporter
Like flattop mentioned, write it down. With the compression release,the butterfly open,the valves closed, cold, hot and how many rpm's it is spinning, even what the barometric pressure is at the time will all influence the test results.
Instead of using an electric starter, where the amount of charge in the battery would have an effect I used an electric hole hog drill plugged in.
Then wrote down the 1200 rpms that the tack showed while testing the LO206. The result was a number that seemed like the compression release was deactivated yet I was sure it was a number I could rely on to compere to the next time I tested it.
Then if I see that the compression is lower than my notes show it should be I would then do a leak-down test to see why.
Instead of using an electric starter, where the amount of charge in the battery would have an effect I used an electric hole hog drill plugged in.
Then wrote down the 1200 rpms that the tack showed while testing the LO206. The result was a number that seemed like the compression release was deactivated yet I was sure it was a number I could rely on to compere to the next time I tested it.
Then if I see that the compression is lower than my notes show it should be I would then do a leak-down test to see why.