Blowby Fix?

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Jan 15, 2004 | 10:20 PM

SSnakekiller

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From: Fort Lauderdale

Blowby Fix?

After turbo install i got the common blowby-popout-your-dipstick-oil-splatter-all-over-under-hood thing and I am just wondering if any of you are familiar with this procedure and if it will help or not?

http://www.hovis.cc/Firebird_HTML/pcv_mod.htm

Engine runs fine, just had blowby. Compression test is on the way just to make sure rings/ringlands are ok.

Thanks

Jan 15, 2004 | 11:46 PM

QuickSilver2002

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Joined: Apr 2002

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From: Austin, TX

Quote:

Originally Posted by SSnakekiller

One of two things is happening.

1. You have excessive blowby past the rings and the pressure has nowhere to go under boost (except out the dipstick).
2. You are actually pressurizing the crankcase with boost via the weak PCV valve (or you forgot to cap the PCV fresh air nipple in front of the throttle blade).

# 2 can be fixed with a simple check valve.

#1 can be prevented by capping the PCV and venting to atmosphere with a breather or two. You could probably also eliminate it by routing all lines to a sealed catch can + adding a line that goes to the turbo compressor inlet (This will allow blowby to evacuate under boost, but it can kill your octane).

My experience tells me there is really no decent choice on a stock motor besides venting to atmosphere. The oily blowby gasses going back into the compressor caused my motor to knock badly.

I did a leakdown and compression test on mine and one piston was a little off at 10% leakdown (the others were all 5-7% and compression was perfect). My car also still runs great, but I have way too much blowby and will be doing a forged shortblock shortly.

Bottom line, the stock rings suck for boost. Oh yea, the pistons are not so great either.

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