High compression readings?

[4wdchico]

I'm getting 190-197psi compression readings, 3ac 141k miles in my '85 4wd terc. Strange thing is the compression went up (was mid 180's before) after doing the full Seafoam smoke out the 'hood treatment.

Any ideas?

[splatterdog]

I measured 207psi on my 200k donor right before transplant. I decarboned as well about a year before. I use berrymans b12 instead. Makes seafoam look like water for carbon removal. I do the good old down the carb method followed by distilled water. I also put a can in the oil when the engine is cold. Run till fully wamed up without revving. DO NOT rev or drive as b12 is 100% solvent and will reduce lubrication. Then change oil. Repeat at next change if its nasty. I also wouldn't do this method with questionable oil in a "new" car. I'll change it first with the cheapest "throwaway oil" I can find, usually "farm rated" diesel spec 15w40 which also offers higher detergency for the task.

This undoubtedly freed up all the piston rings to some extent. It ran noticeably better after treatment. And oil consumption/smoke were greatly reduced and eventually almost nonexistent after switching to synthetic oil. Minimum blowby too, zero oil in the air cleaner housing and the oil stays cleaner longer.

Don't know if this is why my readings were so high. Didn't do a before measurement. As far as the previous owner knows my engine was still 100% original. Has your cyl head been shaved for a new gasket? Most others here have posted about 150psi and 207(or even 197) does seem a little high for 9:1 compression.

What I think it means is, if the bottom end holds up, your engine may have a very long way to go. Enjoy!

[4wdchico]

Ok, I guess that there is not too much to worry about. Thanks for the info. BTW: B-12 is 70% acetone and 30% toluene, check the MSDS. So you can just make your own if you feel like it. Yes, that stuff will clean out the lubricated parts of an engine really well. I just was into my valve cover and it looks really good & clean. Changed the valve stem seals & eliminated all of the clouds of smoke after idling a while issue. I think that I'll do the pint of kerosene thing, with a small splash of acetone, just before changing the oil rather than going all out with the B-12.

Good call on the "all fleet" 15-40 wt oil to clean stuff up, I run gas diesel rated oil in everything all the time and it works great. I have been running a mix of 20-30% Shell Rotella T full synth. 5-40 wt and the balance of Rotella T 15-40 conventional oil in all my 4 stroke engines for a long time now. That includes my Honda brush cutter, lawnmowers, 2 terc's, F150, FS Bronco and F250 diesel.