Some blowby #4 low pulled piston and nothing wrong??

[Ron]

That pretty much says it all. My turbo blew and made a real mess but at the EXACT same time all of a sudden i started getting some blowby out the dipstick tube.

I did a compression check and all pistons were 130-135 except for #4 which was about 115-120. And this is the cylinder that my EGT is tapped for. I know my temps have been fine and pulling the head revealed i was running **** rich too. So i popped the piston out anyways and it looks perfect. I even took off the top two rings and they look fine too.

The only question i have is with the hastings rings i know the dot goes up on the second ring but on the top ring is that beveled edge suppose to go up or down? B/c it was up and on the second ring even though the dot is up the edge is down. Any ideas?

Im kinda at a loss as to what i can do to find out why #4 had low compression. The only option i can see at this point is to buy new rings and rering the whole engine again since nothing is wrong with the piston.

Oh and the pistons i am using is the Ross racing Forged pistons. .020 oversized.

I need help in a bad way as i wanted to have the car ready for Cliffs Mopar Day at Cecil and the Mopar Atlantic Nats.

All help is appreciated! Oh yeah this is an 89 CSX with a common block engine.

[iniviate]

when my turbo went out i had a whole lot of blow by. made me pretty mad, because it's a fairly new motor. i changed the turbo, and the blow by went away. all i can figure is that it was leaking boost into the crankcase via the oil drainback tube.....

i would re-ring #4 and let it ride...

[fortknox82]

Yeah im probably gonna rering it and let it ride since i dont know what else i can do. I know i tried to ask people on the board if the turbo could leak boost back into the engine and they said no. And i dont know what else could make the cylinder low on compression unless its the rings or a valve isnt seating.

I just hate having to take it back apart if this doesnt cure the problem b/c i dont have anywhere to work and finding the time to work on it is very rare.

[turbovanman]

Blowby is ring seal, plain and simple. If you have blowby, you have a ring problem or cracked piston. I would hone and rering and you will be fine!

[iniviate]

i'm very sure my turbo was pressurizing the crankcase....

[turbovanman]

Quote:

Originally posted by iniviate i'm very sure my turbo was pressurizing the crankcase....

Hmmmmmm, interesting!!!!!!!!!!

In his case though, sounds like ring seal!

[igotaneed4speed]

i had the same problem with mine the first time i got it togther four yrs ago.... ended up being the turbo was a brand new one froma local import speed shop had a bent shaft that whiped out seals and pressurized crank case massive blow by....!!!

[cletis234]

In every re-ringing issue the dots go up and so do the edge also goes up, unless you had custom rings made, and I would still bet they go up also. The edge has always gone up, if you don't they never seat properly and you get blowby.