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Old 07-13-2016, 12:17 PM
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Is it normal to see some smoke come out of the breathers on a SBC with out a PCV valve?

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Old 07-13-2016, 12:33 PM
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if you have access to a Tachometer.. a digital tachometer.. like on a digital dwell meter...

if you block the PCV flow at idle... you should loose between 50 and 70 RPMs.

this lets you know that the PCV valve you have is close to the proper calibration..

you will also want to unplug the PCV valve from the end of the hose and verify the engine will stall... or there will be a MASSIVE HISSING noise from the end of the open hose.. the PCV hose should have no restriction with the valve unplugged.

you should also have 13/32, 15/32 19/32 emission/PCV hose..

if you don't have enough PCV flow.. you could have issues like scuffed pistons.. broken or worn piston rings. a compression test is the next step.. followed probably by a cylinder leak down test..

during high speed or acceleration when the manifold vacuum drops.. there is not enough suction to handle all the blowby.. so it comes out the vents..

if you cover the breather opening.. if you have just one.. in 10 seconds covered when you pull your hand away.. you should hear a pop as the air rushes back in...

EDIT... yes.. without a PCV you will have oil vapors and residue coming out the breathers..
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Last edited by 69612; 07-13-2016 at 12:38 PM.
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Old 07-13-2016, 02:29 PM
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That was my problem on my 29 Ford. Without a PCV valve it was leaking oil out onto the exhaust headers and blowing back onto the winshield. Installed new rocker covers with the breather holes lined up with the valleys in between the rockers and installed PCV.

That was this thread...

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Old 07-13-2016, 05:55 PM
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Originally Posted by Firsttimechevyowner View Post
Is it normal to see some smoke come out of the breathers on a SBC with out a PCV valve?

If it doesn't have a road draft tube and an open breather on the oil filler tube next to the thermostat housing it needs a pcv system. You're building a lot of crankcase pressure and eventually it will cause major damage.
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