302 blowby
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Senior User
Joined: May 2001
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302 blowby
I have a 302 in a '78 f100.Right off idle it
almost impossible not to have the 4bbl kick
in.It has a 4010 holley 600 with vac secondaries
and i have the stiffest spring in it.What is really
puzzling is that the motor seems to have alot
of blowby at hiway speeds.Goes thru about 1
quart a week.I have tried a different holley,
made sure i had a good pcv system and nothing
seems to make a difference.It never smokes
and the plugs are clean.Any ideas?
almost impossible not to have the 4bbl kick
in.It has a 4010 holley 600 with vac secondaries
and i have the stiffest spring in it.What is really
puzzling is that the motor seems to have alot
of blowby at hiway speeds.Goes thru about 1
quart a week.I have tried a different holley,
made sure i had a good pcv system and nothing
seems to make a difference.It never smokes
and the plugs are clean.Any ideas?
Post Fiend
Joined: Feb 2001
Posts: 6,328
Likes: 124
From: Iowa
302 blowby
Are you talking about the engine pushing oil/oil vapors into the aircleaner, dipstick tube etc? Or just oil consumption in general. A quart a week doesn't tell us too much. Is that a hundred miles? A thousand? 302s were notorious for blowing oil into the air cleaner through the crankcase ventilation hose when they start to get tired. The rings let more combustion pressure by then the PCV system can ventilate. It is usually cause by poor ring seal and can sometimes be pinpointed to a particular cylinder if you do a cylinder leakdown test. About the only cure is to rebuild the engine. The good news is you could drive for years like it is if the oil consumption doesn't get so severe the plugs foul. One other remote possibilty is the drain back holes in the heads are clogged and trapping oil up top. That is usually accompanied by smoking though. Hope this helped. Don't waste your money on "engine rebuild in a can"
Dewayne
Dewayne
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Senior User
Joined: May 2001
Posts: 166
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302 blowby
Thanks for the reply,i drive about 200 miles a week when
it uses the quart.Every once in a great while the motor will
smoke when i first start it up,figured i had a bad valve seal.
But this is very far in between times.
it uses the quart.Every once in a great while the motor will
smoke when i first start it up,figured i had a bad valve seal.
But this is very far in between times.
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ford_pickup
1973 - 1979 F-100 & Larger F-Series Trucks
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Aug 3, 2011 11:05 PM
