safe compression readings

[mo' parts]

only 93 miles on motor. ive checked compression at 10,64,80,93 miles. checked religously, anyway the readings have been 115 on all, every time.
i did a dry and wet test back to back today, cause i was told my compression was low. 115 dry and 140 wet.? are they not seated, or are they washed out from being rich? i have turned down my f. press to about 30 psi at the 64,80 mile mark cause the plugs were sooty. they are clean now, but when the motor is warmed up for a while it will smoke when revved(in nuetral) slightly. is this cause for concern or just drive it? this same motor before cracking 2 pistons at 22 psi (stock pistons) was 130 psi until about 1200 mi. then it was 140 ish. nothing changed except .020 over with venoilas.
would the larger bore and 3cc deeper dish cause this lower reading?
im afraid the turbo, valve seals, or rings are leaking. the head(reconditioned with seals and guides) and turbo have 1600 mi. on them.

any ideas, thoughts or comments? any help is very much appreciated.hate to take all apart a third time lol.

[mo' parts]

someone at least has to have some examples?

bump, bump!

[cybermrc]

How did you break the engine in initially?

[mo' parts]

just the usual 30 minute start up. then on a back road do like 30- 50 mph blasts, on and off the throttle. then drive it normally, not abusing it. only seen 6-10 psi very breifly. though the stage 5 was extremely rich. the fuel is down to 30 static.

everyone is telling me to just drive it. the ring end gaps were set at .019 for the top and .017 for the second. the piston clearance was set at .007 so they are noisy at first.

[cawcislo]

My common block 2.5 0.020 over venolia's seated nicely, but my compression was too high I think. I just did compression check last week after about 6000 miles. 130 all the way across except one cylinder which was 128. Compression check was done with motor at operating temperature. I pulled all the plugs and did a cylinder at a time. I let the car crank over 3 or 4 times with the gas pedal to the floor. Car ran perfect at 12 psi no detonation or anything. With stage 5 at 15 psi graingered I had detonation so I just swapped in a head shim yesterday. I'll do compression readings later today and let you know what the new compression is.

[glhsken]

Compression of up to 150 is perfect. 130 is no where near too low. 115 is getting there.

Yes, Considering you added 3cc's to a 15 cc dish, I think it would have a LARGE impact. You added 20% to the dish volume.

[cawcislo]

Well, I said I would post compression readings after new headgasket and copper shim. old readings were 130,130,130,128, new readings, 130, 135, 134, 130. Go figure, with the shim I gained compression in some cylinders, probably not, the headgasket is probably just sealing a little better now. Again readings will probably vary between guages, due to all kinds of factors and how the compression test is performed, etc.

[1985ShlbyChrger]

I have about 125-127 all across the board in my car. Stock rebuild, cast Mahle pistons .020 over. Rebuilt about 600 miles ago.

[Stratman]

You guys should feel really good! I've got 85% leakdown on my 4th cylinder

[cybermrc]

Quote:

Originally Posted by adam89shlbydayt just the usual 30 minute start up. then on a back road do like 30- 50 mph blasts, on and off the throttle. then drive it normally, not abusing it. only seen 6-10 psi very breifly. though the stage 5 was extremely rich. the fuel is down to 30 static. everyone is telling me to just drive it. the ring end gaps were set at .019 for the top and .017 for the second. the piston clearance was set at .007 so they are noisy at first.

You say it was running extremely rich; that kind of worries me. Sounds like you broke it in correctly, but the running rich part is very bad for ring break in. Your ring gaps are good. I set my upper at .016 and lower at .012 I think? Not sure on my piston clearance, but I'll bet it is similar to yours.

My cranking compression was like 165-175-175-180 when I last checked (!).. kind of high I thought, but I am not worried.


Give your rings a chance to break in. Some take up to 1500 miles! Sounds stupid, but it's true.. If after x amount of miles you show no improvements, and you are certain your cam timing is correct, etc, I'd consider new rings perhaps. But I think you'll be alright. Just stick with it.

[mo' parts]

i feel a little better now, i guess. being that rich worried me also. im gonna find a stock comp. for future break-ins, to be on the safe side. its parked right now till i get the walbro put in. it barely wants to start now. a wore out cam could affect it also, correct?(compression)

ill just drive it and see what happens. thanks for the replies!

[mo' parts]

well walbro is in, but still not wanting to start at all... takes forever to grab. might have to start another thread to get some ideas.

anyway like the first motor i guess it takes a good 200 miles to seat the moly rings properly. did alot of city driving the past couple days, have 185 on the clock. did another compression check today, 140+ on all. yeaaaa.

now if i could get it to start when I want it to and not when it wants to. and still have a intermittent (blue) smoke at idle and when revved............ one thing after another, or should i say one thing at a time, doh...

[cybermrc]

Actually a worn out cam will show no ill effects on compression. It will read normal compression readings.
I had a Dakota 2.5L that had a cam broken in half once (didn't know it at the time I checked compression); and I checked compression on all 4 cylinders and all were normal. Later on of course I figured it out; what a pain. Sometimes the answers to the most difficult problems are the simplest.

[cybermrc]

Glad to hear your rings broke in!

hmmmm My newly built motor has only 110 110 115 110 and I have some bad leakdown

87%
89%
87%
89%

I am going to try unhooking the turbo and turning the fuel pressure way down (enough to keep it running good)

with the turbo unhooked it wont be as apt to push gas past the rings and they will be able to seat better

I am running a stage 3 comp from fwd and 804 injectors (these injectors are weird because I hit 20lbs of boost on them with no detonation, I bet they are flowing at 38lbs like mopar claims they do)

I only have around 300 - 400 miles on this motor and of course with the gas getting in the oil by getting past the rings they are never going to seat