compression check 59 a-b

[oldford2]

Just did a compression check on our 46. I know it should be done at operating temperature but did it cold. 6 cylinders @ 90# and 2 @ 80+#. Engine doesn't burn much oil (leaks and burns 1 qt/1000 miles) and runs great and strong. So my question is: What numbers should I expect at operating temp? Thanks
John

[OLD...BILL]

John; Be happy with what you got, was the carb held wide open all the time with air cleaner off and did you pull all the plugs.?? not half and then the other half. ?? Maybe 110 to 120 would be max ?? You might do it dry and then MMO in all cyc crank it over ( get all oily ) cover the engine with old newpaper when cranking, then check again, its a good test .... OLD....BILL

[oldford2]

Old Bill,
Thanks for your comment. Yes, all plugs out and carb wide open. John

[Ronnie]

Put the plugs back in and drive that bad boy.

R

[ken ct]

Your good to go John,keep driving it,fix the windshield. Good to see you and the wife again at Rhinebeck. ken ct.

[ford1]

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hmmm, looks like exhavaeroto just snuck some spam on here . LOL

[rotorwrench]

Doing a cold compression will tell you what you have when you start that bad boy up. Sounds OK to me. 50 psi or less and I'd start er up & check again.

I do differential checks on aircraft cylinders cold. 80 PSI input pressure should give me near 70 to 75 PSI differential (leakage through rings and other things). The only time I do them hot is if they are abnormally low. That way I can tell if the rings are lined up or something is wrong. Rings don't stay lined up long and crap under the valves will be blown out by the start up and pulling power. Otherwise, cold is good enough.

The old flatheads are still the easiest motors to check bar none.

Kerby