PCV valve and leaking valve cover hole - JeepForum.com
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post #1 of 3 Old 02-07-2010, 02:37 PM Thread Starter
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1986 CJ7 
Join Date: Jan 2008
Location: Madison
Posts: 78
PCV valve and leaking valve cover hole

1st of all I have an aftermarket holley carb so I don't have all that normal emission stuff. Does it make a difference whether the PCV valve is in the front hole or rear hole? There are 3 holes on my valve cover, the 1 furthest to the front has a vent in it, the next hole back is plugged and the 1 in very back has the PCV valve in it. The middle hole (plugged) is leaking a little oil. Should I place the pcv valve in the rear or should I put a tee in it and try to get vapors out of both front and rear hole? Ideally, I would get a OEM type housing and I would be able to run one to the air filter and one to the carb. What are your suggestions. I am kinda at a loss of what i need to do to keep from having oil come out of the valve cover. Oh and I know it doesn't try to come out at idle, must be when i drive it.


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post #2 of 3 Old 02-07-2010, 04:29 PM
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1984 CJ7 
Join Date: Nov 2008
Location: Hazel, KY
Posts: 1,255
when i hooked up the weber carb on my 84 model with 4 banger

the little 4 banger has two holes in top of valve cover, rear hole is the inlet of filtered air from breather (inlet air should be filtered so dirt is not sucked into engine valve train)

front hole is hosed to carb vac and split off to power brake manifold.

system works good.

little 4 banger pulls a lot of vac through pvc valve, so I have never had any oil leaks in this area.
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post #3 of 3 Old 02-08-2010, 06:44 AM
Mike Romain
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1986 CJ7 
Join Date: Nov 2007
Location: Off the Grid in Chester Grant
Posts: 18,083
Some valve covers have splash guards inside them for the intake air hole and PCV so you should have the PCV in the correct place. On a 258, that is the front hole.

The back or other hole has to have filtered fresh air going in.

Your middle hole is just plain leaking and needs to be fixed by the sounds of it. The 'help' line of parts have grommets of differing sizes and you may even need some gasket maker to seal it up or your PCV flow is off so it is blowing oil....

The stock 86 CJ7 PCV valve relies on the input from the charcoal canister (gas tank vent) to have the correct suction for your engine. there should be a T fitting in the PCV line to pick up the canister purge line. The PCV controls engine sludge so it is kinda important it works right. The gas tank also needs a vent and the canister is the best way to do it. It doesn't rob power, it just makes the PCV work correctly.

86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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