how much blowby is acceptable?

[AC sports]

New engine assembled and clearenced by me personally. European in line 4 cast iron block 85mm bore.
New JE forged race pistons 10.5:1 comp ratio. 0.08mm piston to wall clearence. JE proseal rings. Top ring gapped by hand to 0.38 mm. Oil rings fell within spec. Block was bored and honed by machine shop. I gave it a dozen strokes with a 320 grit flexhone before assembly.
On initial start up engine fan failed to kick in and temp went into the red zone but I immediately shut it down. Integrity of the Mls head gasket seems ok. Ran it in on the road at 50% throttle varying load and rpm for 50mls. Dropped oil and continued the process for another 600 mls progressively increasing load. Mixtures are spot on at 12.8-13 :1 under wot.
Problem is the crank case breather pipe is pushing out white smoke at idle. Top of pistons look a little wet in places.
I haven't done a dry/ wet compression check yet but beginning to worry.

[In-Tech]

Block was bored and honed by machine shop. I gave it a dozen strokes with a 320 grit flexhone before assembly.

Why the flex hone?

[AC sports]

I figured with the thin ring pack 1mm, 1.2mm, 3mm they wouldn't need the coarse finish and better at 320.

[mag2555]

White smoke is steam from water so you must be seing water in the oil and or steam out the Exh also!

[AC sports]

It's oil smoke. Sorry if I was unclear. Most people call it blue smoke. ... I've never seen it as blue.

[Charliesauto]

New engine assembled and clearenced by me personally. European in line 4 cast iron block 85mm bore.
New JE forged race pistons 10.5:1 comp ratio. 0.08mm piston to wall clearence. JE proseal rings. Top ring gapped by hand to 0.38 mm. Oil rings fell within spec. Block was bored and honed by machine shop. I gave it a dozen strokes with a 320 grit flexhone before assembly.
On initial start up engine fan failed to kick in and temp went into the red zone but I immediately shut it down. Integrity of the Mls head gasket seems ok. Ran it in on the road at 50% throttle varying load and rpm for 50mls. Dropped oil and continued the process for another 600 mls progressively increasing load. Mixtures are spot on at 12.8-13 :1 under wot.
Problem is the crank case breather pipe is pushing out white smoke at idle. Top of pistons look a little wet in places.
I haven't done a dry/ wet compression check yet but beginning to worry.

Typical Small block V-8's are usually around 3 cfm on our dyno. That's full load and throttle from 4500-7500 rpm.

I would think a 4 cylinder should be roughly 1/2 that.

[pamotorman]

that could be condensation moisture in the oil boiling out.

[mag2555]

Are these rings used Moly face ?

[AC sports]

Rings were new. Pretty sure top ring had a chrome plating on it or at least similar.
Interesting you give me a figure in cfm. How are you measuring it given its low pressure?
Condensation in the oil after a hard 30 min run ? I don't see how. Sorry if I was unclear on that.
Would a dry followed by wet compression test be conclusive it's a ring seal issue? I'm thinking either my bore finish of 320 flexhone ( much finer than a 320 stone finish) was too fine for the top rings to break in or I've somehow glazed the bores. I may try an arthroscopic camera down the plug holes tomorrow. Maybe that will show bore condition.

[MadBill]

...Interesting you give me a figure in cfm. How are you measuring it given its low pressure?..

Google "engine blow by meters" or look at Dwyer variable area meters http://www.dwyer-inst.com/Products/TOC. ... i4EALw_wcB

[mag2555]

There's no getting around it that top ring has a chrome face and your 320 grit flexhone session is keeping that ring from breaking in!

[houser45]

There's no getting around it that top ring has a chrome face and your 320 grit flexhone session is keeping that ring from breaking in!

No doubt, i would have finished with 600 grit stones for this. Leave the flex hone on the wall

[groberts101]

There's no getting around it that top ring has a chrome face and your 320 grit flexhone session is keeping that ring from breaking in!

Yep. 220-240 stoning with a VERY quick 320-400 plateau hone would have helped those hard chrome rings seat.

I have seated rings up by running a PCV valve on a completely SEALED crankcase(don't forget to o-ring the dipstick too). Then put some miles on it with idle and moderate throttle only. Compression brake the hell out of it down hills too. If you also use a header evac in conjunction with the sealed crankcase PCV setup then you can also run full throttle as well. It works much of the time and sure beats a full teardown.

[AC sports]

So the question now is, how do I get them to seat? It's just ticked over 1000mls now. I've got the crank case breather venting to atmosphere ATM.
I do live in a very hilly area too!

[ptuomov]

The blowby is proportional to average cylinder pressure and thus torque. We’ve got about 2.5 CFM from a 5L / 303 cid twin turbo V8 at 500 lbf-ft.