ryansmig

Holy ****, I was reading this and saw 2023 on most posts so I was surprised to see it say "Yesterday". Anyway.

I'm interested to hear what your compression numbers were during the dry tests before? I am having similar issues with a fresh rebuild (top and bottom). Prior to rebuild, compression was around 185 on all cylinders after 2.5 years of abuse. After, I'm seeing about 183, but with looser tolerances so I'm not surprised. I also knew my oil drain was kinked in places and inadequate for 6258. Fresh build I gapped rings to 0.019" as opposed to the 0.012" that the old motor had (because 12 thou is to way too tight). Now I'm experiencing what I can only consider to be a crazy amount of blowby and still have occasional puffs of smoke after high boost. Plenty of high vacuum following this will tend to clear up the residual oil and stop smoking

Roundlake

iTrader: (1)

My compression numbers on the rebuilt engine dry are 149 psi. I don't know what it was before the rebuilt. I assume around 180-200?

I think your ring gap is fine. Mines 0.018. I think the issue lies with something that the machine shop did wrong on mine.

ryansmig

Ah yeah 149 does seem pretty low. Were they all around ~150 or just some of the cylinders? Any idea how fine/coarse the hone was and if the shop used a profilometer to verify correct roughness?

Roundlake

iTrader: (1)

Every cylinder is 149psi. Ive got no idea what the machine shop did. (Trusted and highly recommended shop)

Im going to give them a visit soon and report back.

Midtenn

iTrader: (15)

If every cylinder is low but equal, it's likely the tester and not the engine. Engines rarely fail evenly.

Many cheap compression testers are built wrong to get good numbers. A good compression tester should have the Schrader valve in the spark plug end of the adapter hose. That way only the air in the cylinder is being compressed. Cheap ones (like from Harbor Freight) have the Schrader valve in the gauge. Then you are compressing the air in the cylinder and the hoses (along with loses in the QD).

ryansmig

Yeah @Midtenn I've heard the same thing. I'd say his is accurate only if he used the same tester when he checked pre-rebuild or if he has tested on a known good motor

Roundlake

iTrader: (1)

I used a brand new snap on compression tester. But I think you guys are missing the point here..... you can't have over 60psi gain when doing a wet compression test. That means the rings are leaking badly...... but for argument sake the cheap compression tester I've got read only 1 psi difference from the snap-on.

ryansmig

I mean yeah they shouldn't go up that much unless you're adding a whole lot of oil. I'm just playing devils advocate