Compression test results. Please read

[Structure240sx]

Did a compression check finally today. First for those that dont know i got my car running when i realized it was jsut the coldpipe that blew off the intercooler. ran fine for a day then started smoking under boost. today it was smoking without boost. the smoke was most white possibly a blue tint hard to tell while driving and lookin in mirrors. i did a compression an hour ago and got these results within a couple psi

#1 - 180psi #2 - 180psi#3 - 70psi#4 - 100psi

i ordered a new headgasket today and it will be here tomorrow morning. i figure its the HG cuz of white smoke and 2 adjacent cylinders being very low. i havent changed a HG before but doesnt seem like it will be too much. only part i dont feel like doin is the two brackets and all the coolant hoses on the intake manifold. removing and installing the cams doesnt bother me tho go figure. to those u hav done HG i figure it will be best to use and engine lift to pull the head since the intake and exhuast mani with turbo will be pretty heavy.

[Nathan]

Nah, it's not that heavy...I took mine off with the manifolds still attached and it wasnt a big deal...although I had a friend helping me, just set on a towel once we got it off.

[fiznat]

I donno man.... it could still be rings... especially with numbers that low... Id smell my oil for any gas smell, and BE SURE...

[Structure240sx]

But it should be the HG for sure right? i dont want to do all this then have to swap out the engine. And how long did it take u to change i'm thinkin very conservativly 6 hours cuz nothin ever goes jsut as planned

[RaVeD240sx]

:rolleyes Lets see i just finish changing one (91, 240sx KA24DE) and took me (one person only) like 8hr's no joke .. i took the head by its self ( i had too resurface, pressure test) no intake mani or exhaust mani .. oh and watch out for the timing chain's and make sure you know what your doing when taking out the Distrubutor..(my timing was way off when i put everyting back together).. P.S.. leave everyting at TDC before you do anyting, its much easy'er too put the timimg back together...:ylsuper

[Structure240sx]

yea i know about that timing thing. i took apart most of my engine before cuz i thought i was goin to go SR. why did u get the head resurfaced, was it warped?

[RaVeD240sx]

well the engine had a blown HG, and i was under the impreession that it was due too high temperatures, and that let me too the conclusion to do a pressure test and resurface the head.. main reasons for the conclussion 1.over heating problem 2.hell of alot smoke(white and blue at some times or both)3.water level droping tofast 4.oil consumption and yes the head was warp... :thinker

[Structure240sx]

yea i was thinkin about it. my engine didnt over heat at all jsut alot of smoke after seeing boost now more without boost. my egt's didnt go past 1450 degrees and was only that hight for a second or two. aluminum starts to melt after 1500 right. but yea the engine hasnt over heated

[Structure240sx]

yea so the headgasket looks like its brand new. definitly piston rings. on the cylinders that were still good the exhuast valves are all white whats that from

[Pornflakes]

The rings are fine. You broke the ring lands on #3 and #4....

[Structure240sx]

isnt that where the rings seat? how could those break and the rings. im just goin to throw in my built engine or sell it and get another stock ka to put in it

[Pornflakes]

I don't think the rings are broken. Just the ring lands on #3 and #4 (that's where the rings seat).

[:: orion ::]

Yep...I'd go with ring lands.

Oughta look kinda like this...

Later - Brian

[Structure240sx]

so basically its the actual piston? guess i might not sell my built engine and throw that in unless i can sell it like now and pick up a stock ka

[PMan_S13]

how'd you guys know it was the ring lands instead of the rings themselves?

did you interpret the readings, or is it just from experience that the lands themselves break before the rings do?

[:: orion ::]

We're clairvoyant...

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No, it's experience...check the link in my post above. I broke a ring land. Stock KA pistons don't take to detonantion well, but the rings hold just fine it seems. So the pistons crack rather than the rings breaking.

Later - Brian

[PMan_S13]

huh, I find that pretty interesting.. so the KA's rings have decent strength to them? I knew the pistons were a weak point; but I didn't know they were that weak.

I checked the link.. so when your piston popped did you end up with pieces in your oil pan or scoring on the cylinder wall? or is the only symptom low compression reading after it has detonation?

[Projex240]

I hate the white smoke....I think mine went, but putting a new motor in is easier than changing out a head gasket anyway.

[Pornflakes]

huh, I find that pretty interesting.. so the KA's rings have decent strength to them? I knew the pistons were a weak point; but I didn't know they were that weak.

I checked the link.. so when your piston popped did you end up with pieces in your oil pan or scoring on the cylinder wall? or is the only symptom low compression reading after it has detonation?

Yep....they're THAT weak.

When they break, they usually stay in place (just cracked into a piece or two). The only way to know without taking the engine apart is to do a compression test (very low compression on that cylinder).

[Structure240sx]

yea wish i didnt go through the trouble of takin off the head since im swapping my built engine in tomorrow instead of last week. even look at the piston with the head off its looks fine. just tons of smoke when giving it gas and it was dieing at idle sometimes usually when it was cold

[PMan_S13]

Yep....they're THAT weak.

When they break, they usually stay in place (just cracked into a piece or two). The only way to know without taking the engine apart is to do a compression test (very low compression on that cylinder).

Ohh, so the only way you can be sure is to look at the piston when it is out of the motor.. you can't tell when it's still in?

I figured that would score the crap out of the cylinder walls

[Structure240sx]

i didnt look too hard at the walls but i could tell at all with the head off