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09-17-2007, 05:26 PM
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#1 |
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On a budget like Fred Sanford
Join Date: Oct 2005
Location: Topeka, KS
Posts: 2,031
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PCV valve problems
Ever since putting the 383 in my truck I've had a head-scratching problem with my idle. What happens is it idles fine until you drive it, lol. Push in the clutch after being on the road for awhile and the idle hangs and won't come down.......as much as 200rpm faster than what I have the idle set at. Sometimes it'll even diesel when shutting it down because it's idling so high. Vacuum leak right? I searched religiously and couldn't find one. Well after 3 months I finally figured out the problem, but am not real sure of the fix---hoping someone can help.
Turns out my PCV valve must be hanging fully open after being exposed to higher vacuum levels seen at cruise. When I come to a stop the ball in the valve stays fully open creating a huge vacuum leak which shoots the idle up way high. I removed the PCV valve for a day and the problem completely disappears---idles perfectly. I want to run a PCV on this motor though, so removing it is not a valid solution. So I replaced the valve with a brand new stock one for an '85 c10 w/350. It's a little better, but is still doing the same thing. Now the problem I'm facing is I know very little about PCV valves and cannot find much info about them on the web, the monkeys at the parts stores are all clueless, and there's nothing but a part # on all these identical looking valves at the store. I assume I need a valve that has a heavier ball or stiffer spring or something to hold it closer to closed at idle. Can anyone point me in the right direction? 
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'85 Silverado swb: 383 stroker, 10.5:1, vortec heads, 232/238 roller cam, RPM air gap, performer 750 carb, stainless longtubes, 3" duals/super 44's, T56/4.11 383ci build / exterior refresh thread '98 Camaro z28: 370ci twin turbo 370ci build '01 Tahoe LT 4x4: 5.3, longtubes/ory, magnaflow duals, custom tune....wife's DD |
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09-17-2007, 05:30 PM
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#2 |
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Registered User
Join Date: Feb 2007
Location: Austin, TX
Posts: 3,930
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Re: PCV valve problems
What do you have on the other valve cover ? Breather, Oil Cap ?
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09-17-2007, 05:33 PM
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#3 |
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On a budget like Fred Sanford
Join Date: Oct 2005
Location: Topeka, KS
Posts: 2,031
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Re: PCV valve problems
Breather
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'85 Silverado swb: 383 stroker, 10.5:1, vortec heads, 232/238 roller cam, RPM air gap, performer 750 carb, stainless longtubes, 3" duals/super 44's, T56/4.11 383ci build / exterior refresh thread '98 Camaro z28: 370ci twin turbo 370ci build '01 Tahoe LT 4x4: 5.3, longtubes/ory, magnaflow duals, custom tune....wife's DD |
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09-17-2007, 05:38 PM
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#4 |
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glamoros piece o' lowlife
Join Date: Mar 2007
Location: Redford, MI
Posts: 1,164
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Re: PCV valve problems
Breather on one side and PCV on the other sounds right, that's what I ran too and it was fine, dunno why yers acts up like that. I had to convert to all breathers tho cause my high-volume pump was shooting oil strait at the PCV and teh carb sucked it and it fouled plugs, but even that didn't mess up my idle... and I don't even know what PCV was there, I have like 3 laying around so I just used the first one I found.
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The more I drink, the more I drink, the more I drink... diesel, reg cab, long bed, 4 across the rear, single stack, wooden stakes, and lotsa lights - the Hay Express |
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