compression test results

Well, I started the process, and my friend said "Since you have it open, let's put in new valves for all cylinders." Never should have listened to him, but I did... In the process I reused those cute little buttons on the tops of the valve stems - which according to other posts on this forum may not be necessary any more. Don't know if that made a difference or not.

Buttoned it back up, torqued the head up to 80, and on the first pass up to 90 I stripped a head nut - one of the old crusty ones outside the valve cover. I replaced the stud and nut, and left the whole thing torqued to 84 for an initial test - gapped the valves at .015 cold and now my compression is between 45 and 65 on all four - although the original cylinder is now one of the high values. That's my first question: what's the proper torque for the Z134 engine? This also brings up my second question: What am I missing that caused such a precipitous drop on compression?

I lapped the valves, but did not actually regrind the seats. However, I did get a nice matte ring on the valves and the seats also looked appropriately polished. Haven't had a problem with this in the past, however.

I didn't blow any bubbles (a la a warped head leaking coolant) and all of the valve springs appeared to have good tension. I didn't actually check the compression resistance, however.

Those are about the only things I can think of which would cause such a dramatic drop in the compression, although I'm not necessarily the brightest bulb on the christmas tree at times.

I'm flummoxed, and I feel like a chump - up until this point in time my experience has been olivers, caterpillars, and JD's, and this tractor is beating me so far. Any and all thoughts are greatly appreciated.

Thank you for your time,
Max

Hope this helps.

Regarding the ideal pressure, as I implied before, the ideal equation for the pressure rise due to compression assumes a constant mass in the cylinder for pure air initially at atmosperic pressure. Unless you took the air induction system off (i.e. removed everything between the the out side air and the intake valve, fully closed all the valves after the intake stroke, had no valve leakage and had a perfect head gasket, you won't begin to approach this pressure. My guess is the best you'll ever see on a compression test is around 120 psi for these 6.5:1 compression ratio engines.

Additionally, it helps you (me) to catch yourself if you make a mistake.

Mark