5.0L (1979-1995) Mustang Technical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.

Blow-by?

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Old 01-05-2006, 10:16 PM
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darkstang
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Default Blow-by?

To fill you guys in, I have a '95 with AFR 165's, cobra upper and lower, x cam, 1.6 rr, longtubes, off road H, flows, diablo chip,65 mm t.b., K&N, and 3.73 outback. When I really put my foot in the gas it blows oil out the breather on the valvecovers, and burns the oil off on the header. Note I only have 1 breather thats on the passenger side. I have heard this called blow-by before. My question is what causes this , and how can it be corrected?
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Old 01-05-2006, 10:21 PM
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vfast
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Default RE: Blow-by?

that's not blowby........the good thing I hope your PCV valve screen is clogged or the bad thing you have a compression(s) going bad...
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Old 01-05-2006, 10:26 PM
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darkstang
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Default RE: Blow-by?

then what is blowby?
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Old 01-05-2006, 10:27 PM
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silver91gt
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Default RE: Blow-by?

sounds like your pcv valve popped out of the lower intake.
feel around the back of the intake for it
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Old 01-05-2006, 10:31 PM
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5.0_PR
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Default RE: Blow-by?

Blow-by is when the oil is being pushed up from under the valve covers-if you have a breather, it'll leak oil. If you take of the oil cap when it's running and oil sprays out, that too is blow-by. Definitly check the pcv lines.
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Old 01-05-2006, 10:31 PM
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vfast
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Default RE: Blow-by?

is when oil getting by the rings into the exhaust..
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Old 01-05-2006, 10:31 PM
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darkstang
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Default RE: Blow-by?

can the pvc valve screen be removed or replaced? iv also heard you could bypass this , is this true? ............ and yes my pvc valve pops out all the time and am forced to but it back. I have replased it but it didnt work.
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Old 01-05-2006, 10:32 PM
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vfast
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Default RE: Blow-by?

I just make mine also replace the rubber gourmet
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Old 01-05-2006, 10:36 PM
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kartracer55
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Default RE: Blow-by?

Blowby is when youve got the fuel mixture escaping past the rings on compression and the combustion escaping on the power stroke... it all goes into the crank case. Alot of times the oil will appear a greyish color too. The PCV valve VFast is refering too stands for Positive Crancase Vent Or Ventilation or something. The PCV valve sucks all the gases that escaped out of the crankcase (using intake vacuum I presume) and sends it back through the engine... If the PCV valve isnt working, a bit of oil and blow by will blow through the breather... sometimes its in the valve cover, sometimes its routed right to the air filter.

If ive got something wrong, correct me. IF you can explain it better, do it. Dont wanna confuse anybody

Jim
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Old 01-05-2006, 10:37 PM
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darkstang
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Default RE: Blow-by?

great ill check this out thanx guys
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