I ran a compression check when I got my motor running after installing my new head. Cylinder 1 was 180, cylinder 2 was 160, cylinder 3 was 175, and cylinder 4 was 190. Well after putting 150 miles on it I decided to test it again startin from 1 to 4 I got 180, 150, 180, and 185. Cylinders 1, 3 and 4 are good but 2 dropped 10 psi. Is cylinfer 2 way too low? and can it cause issues running with a cylinder that is as low as that?

 

i'd give it a feew more miles for everything to settle in. about 500 miles i would check it again........ but yea, it is a bit unsettling to see those numbers. if you added a new head to a fairly worn bottom end, it may cause it to further weaken those compression numbers since you'll have better sealing up top... the worn rings will let the pressure go easier than the top........ know what im getting at?

 

Are you doin the test with engine at op temp or run a cyl leak test as well, my 3 and 4 have 40 and 60% leakage out oil fill cap, must inject 100 psi of air with cyl leak tester and shop air.

Cyl at TDC compression stroke for cyl bein tested done same as compression testing op temp and 5 puffs.

If you:

Open oil fill cap and here the air injected into cyl its rings
Out of exhaust or intake TB its valve not closin due to valve issuses
Out of spark plug gally of next cyl is head gasket between two cyls

Hope any of this helps out.

 

I was testing it at op temperature. One thing I forgot to mention and the reason me and my dad have been keeping an eye on the compression. The top of cylinder 2 was scarred badly by something (we think it was the mechanic that replaced the head gasket before we redid it who caused it). The cylinder walls still had the crosshatch marks so we decided we would just keep an eye on compression. I will continue to check it and if the worst should happen I have a spare 22r in my garage that I can replace it with until I can get the issue fixed.

 

the 150 and 185 cylinders have a 19% difference between the compression, at 20% i tell people at my shop that we need to do a leak down and probably tear the head off. On a new motor rebuild I would say there is probably installation error somewhere are you are going to have to re-check your build. Sorry