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Unread 03-17-2002, 11:06 PM   #1
jrejle
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1974 258 PVC Valve and breather

I recently purchased a 1974 CJ5 with a 258 and I am having a lot of problems with oil in my air cleaner housing. I was looking at the valve cover and there is two hoses coming from the valve cover. The one forward by the oil servicing cap is connected to the PCV filter in the aircleaner housing. The other one is located in the aft portion of the engine and it has the PCV valve in it and is connected to the manifold. Looking at the Haynes manual the PCV valve should be in the forward hose and the aft hose should connect to the pcv filter in the air cleraner housing. My questions are does it really matter? Can I completely iliminate the breather? How does this set up work with an aftermarket chrome aircleaner housing. I am tired of oil dripping on the exhaust manifold!
Thanks Jim

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Unread 03-18-2002, 11:39 AM   #2
4wheeler4CJ
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When I got my last '77 CJ-7, 258 bone stock motor, the front hose went directly to the hole in the front of the air cleaner, the aft hose went to the manifold with a pcv valve.

Do a compression check on your cylinders. Follow the "dry" or regular procedure first to check your actual compression. Then, after you document each cylinder, repeat the test for each one, but first put a few squirts of 20W50 or 30W oil in the cylinder directly before cranking it to get the pressure. Document the pressures again. If you notice a jump in the compression when you add oil, you have weak rings. You can have compression within the allowables when you first do your dry check, but the compression should be the same when you add oil, if it isn't and is greater, you have weak oil rings.

If you are getting that much oil in your air cleaner, chances are that you have weak rings and are getting a some "blow by", causing more positive crankcase pressure than you should have. When that happens, the pressure will start to release through your valve cover vents, and you get excess oil buildup.

If it gets bad enough, you will start to notice your seals start to leak oil, as it actually builds up enough pressure to start blowing seals.

By removing the vent hoses and putting a breather cap in, you will stop getting so much oil in your air cleaner, but it will blow all over your engine and compartment instead, eventually coating everything with oil, then dirt, as the dirt will stick everywhere.

Don't mean to alarm you, but I've been there before, and what you are describing is exactly the problem I had. After a few years of driving it (6 months even with zero compression in #1!), I finally built a 258 motor (modified with Clifford Performance goodies) in my garage and dropped it in when it was ready, all the problems disappeared.

If you find that that is your problem, you can still drive it while you put another motor together, it will just be more of a nuisance than anything, just check your oil often, LOL.

Let me know how you make out, I'm curious now.
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Unread 03-19-2002, 10:06 AM   #3
jrejle
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Thanks a lot for the information. I went to do a compression check and my gauge wont fit so I will need to go get an adapter. I have noticed that when I drive around town the oil isnt near as bad, almost non existent, but when I drive at highway speeds for an extended period, say 40 miles or so, I have a mess on the intake and exhaust manifolds. Ill let you know what I find.

Jim
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Unread 03-22-2002, 03:41 PM   #4
johny1i
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Make sure to check out the YJ Forum post titled "Oil in Air Filter" started by Galvoknight. About 8 responses so far to this 258 question with some good troubleshooting ideas. Last post was March 22 (maybe later by the time you read this).
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Unread 03-24-2002, 07:55 PM   #5
jrejle
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I completed a compression check today and all cylinders were between 105-115 however when I put the oil in the number one cylinder the compression went to 170. All others didnt change a bit. I gues I found my culprit. I went with a larger filter and its kind of crammed up against the top of the aircleaner and so far its working. I guess I need to start preparing for a rebuild later this year! Thanks for the information. BTW, the manual said that the compression should be 150 and I am getting 105-110 out of all of them. Does this mean that they are all starting to get weak?
Jim
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Unread 03-25-2002, 10:20 AM   #6
4wheeler4CJ
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Yes, when my motor got weak, I was getting between 90 - 120 psi, with the number 1 being 0, LOL.

You have your problem, pegged, tho, you're getting blowby. At least now you know

You have plenty of time, tho, now you can plan a rebuild while you drive that one. I drove mine with the problem I had for at least 6 months before I got enough money up to do a motor. (I needed a decent amount, because I built it with all Clifford Performance Parts). A stock rebuild will be considerably cheaper, if you choose that route.
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