Only 100 miles on my motor, but I figured Id test it out and see if I can figure cyl 3 out...This is after ALOT of compression braking and a few 6.5k pulls at the urging of my N/T peers.

Compression test, hot motor, all plugs removed, FI disabled, WOT, at least 10 revolutions on a battery charger. No wet test for obvious reasons.

Cyl 1 2 3 4

120-125-72-130

Cyl 3 has compression but it is weak. Spark plug is same color as others, and the motor is running very well actually, pulling good despite pulling alot of timing out for break in.

Leakdown test, tested cylinders in firing order to make sure they had the same results. These results are for all cylinders. 20 psi regulated into the cylinder while turning over by hand. Air heard leaking at expected points (intake stroke, exhaust stroke). Air had to be removed to complete the compression stroke. At TDC, air re-applied, no air leaking from intake/exhaust, no bubbles in cooling system. VERY very slight air leak can be heard when you pull the dipstick out coming from the tube, but the sound was the same, no stronger or weaker on any cylinder and these rings probably havent fully seated, as well as the fact there will always be some amount of blow by.

Not really sure what to take from this test, other than I cant figure out why cyl 3 is low. Same cylinder as last year, slightly higher number. At first I thought sticking lifter, because when I bled them there were a few that took a few times to bleed, but they were all compressable when installed and I think I would have heard the air leaking thru one of the manifolds on the compression stroke. The other thing that got me was the low compression numbers for 10.5:1 pistons, but maybe thats what I can expect from Crower 2s and 100 mile run piston rings. Any thoughts?

For what its worth, I don't trust compression numbers on a new motor for at least a few thousand miles. :shrug

Thats what I figured, but usually they break in evenly, and the fact that the same cylinder is low by close to the same amount, makes me think that theres one little thing going on somewhere.

Originally posted by Slo2g
For what its worth, I don't trust compression numbers on a new motor for at least a few thousand miles. :shrug

this

You are normally "comp'ed up" by 100 miles. With that being said, I have seen a rebuild go 1500 or so before the rings set (I never took it apart so we never knew exactly why). Not to add to your anxiety, but I'm not really liking what's going on there. No, your comp numbers as the rings seat do not necessarily go in a linear pattern.

I can't remember if you did JE's, but if so, did you use their rings or did you decided to use some special Total Seal ring (of which I don't like)?

Honestly, at this point, you're in for a penny, in for a pound. Put some miles on her and see where you go. Is she running alright?

Mine were all over the place until I had around 600ish miles on it.

What MB said though - number 3 is worrying and the low numbers on the others are kinda iffy.

Mine were never that low.

Theyre wiseco with regular rings. The motor itself seems to be running good. Its definately louder when at WOT. Not really sure on the power because I have at most 21-23 deg of timing at WOT 7k rpm. But it does seem to have more midrange power, and 1st gear has become more of a handful. After 4.5k it often breaks traction. Not sure if theres a problem with the rings seating or if they just take longer to break in, but like you said usually the compression should be close to set about now. Ill keep putting miles on it and see what happens. Should I keep doing some pulls or just do regular stop and go city driving?

Just found out Wiseco had a huge recall on all there 420a 10.5 comp piston ring sets, time to pull apart the motor. Sorry Colby.
















Sorry had to add to the paranoia

Your tester could be bad honestly. If you really had only 72psi in cylinder 3 it would be missing. IIRC you need at least 90 psi to ignite the mixture.

my rings in the 3 rebuilds I did (stock, JE, wiseco) all took over 1500 miles or so to seat (on avg)

Thanks steve lol.

Ok ill keep driving it building up the miles. If its not any better by 2000 miles im probably going to have to get new rings

At 500 miles is when we started considering a situation.

Agreed. Im going to start driving the car to work now to build up the miles. Compression test again at 500 miles?

Well bit of an update here. Slo2g, you were right on the money. My newer comp tester is leaking somewhere. Tested the compression on my Avenger just out of curiousity, and got 125.....I was like theres no way this motor and my Eclipses have the SAME compression. Lo and behold, different gauge, get 150 psi accross the board. So I says to myself, self, you better retest the eclipse.

New numbers, not sure how much due to the gauge and how much due to more milage put on. Currently at 175 miles.

140-140-105-145

That makes me feel a little better, but Im not out of the woods just yet. My rings must be breaking in nicely, because I have decent compression and Im not burning anything at all fluid wise. This cyl 3 is pissing me off though, so here is my plan. Feel free to eliminate/correct any steps in this if you feel neccessary.

1. Pop the valve cover, take out all the lifters and replace them with lifters from one of my other 6 cylinder heads. Bleed, install, test drive, and diagnose.

If cyl 3 is still low,

2. Put the stock cams back in, just to verify that theres something wrong with the cam itself, which Ive always had a weird feeling about this cam in the first place.

And if 3 is STILL significantly lower than the others...

3. Put my other race ported cylinder head with crower 2s on and see what happens then.

Im going in order of ease here. If its not the lifters its the cam, if not the cam its the head. If its not the head I will probably just give up on life and wait for an apocolypse.

Ok so someone try to figure this one out..

I bled and installed lifters from another head using the screwdriver trick. After putting it back together and cranking it, I had that even compression on all cylinders sound, not the obvious low compression whine. Starting the car it automatically ran smoother. First thing I notice though, is the LOUD tick coming from the head. Almost sounded like rod knock. But that faded away as it warmed up. I drove it around for a few hours, then unplugged the injectors and tested compression/starter noise again. Compression on cyl3 went back down, and I had that dead cylinder starter whine again. :| So what is going on here? Pretty sure Ive narrowed my problem down to valves, but I cant figure out why it will work fine until the lifters get some oil in them. Anyone have anything for me here? Im at a loss and Im getting really close to giving up. I dont have the money to be chasing problems anymore.

Bump. I feel your pain.

The tricky thing about lifters is you're probably going to be hard-pressed to find legit specs on installed height or whatever, because the vast majority of DSMers these days don't think about stuff like that beyond replacement.

From our conversations in PM, I think you might have one of the early, experimental Crower 2 grinds, as your numbers don't match up with those of the spec card, so it would really suck to not be able to use them because of one janky valve.

Surely, if this turns out to be a bum valve, someone 'round here could fire off a couple replacement stockers they have left over after going to oversized...

Thanks Driggs. Im actually thinking about just pulling the head. At this point, Ive already had it to the point where I could have removed the head while the engine was still in the car if I needed to, so Ill just tear it back down this weekend. Give me a chance to look at my pistons too. I have another Cylinder head that is actually MORE ported out than my current one, so Ill either swap that one on, or check out my valves in this one and see what the deal is.