Back pressure?

[rls120]

I'll try to make a very long story shorter. . .
My 81 CJ7 AMC 258 i6 / 4.2l slings oil everywhere. . .1-2 quarts on a 20 mile trip!
This is my second engine (all brand new parts) with this problem. If I hook up the PCV system, it sucks oil out of the valve cover and into the intake, making massive amounts of smoke on decel and idle. If I disconnect the PCV system, it just flings oil all over the place through and around the breather filters. When I look through the PCV grommet into the (aftermarket aluminum) valve cover baffle, I can see oil running accross the top of the baffle like a river. . . .at idle. Engine runs great, good compression, no visible blow-by at idle.

The only common denominator here is the exhaust system. Could this be a back pressure issue? I've replaced the Cat, so at this point there's nothing left to change but the muffler.

Do any of you have any ideas? I'm really at a loss on this.

 

[Lumpy Grits]

Where's your breather?
You sure the PCV is installed correctly?
http://home.sprynet.com/~dale02/vac-pcv.htm
LG

 

[Torxhead]

I would question that valve cover baffle and what brand of valve cover do you have?

 

[Hedgehog]

You've had 2 engines do this ....... What is common between the two?

 

[Flex BT]

That is crazy! Interested to see what this turns out to be...

What kind of carb is on your engine? Have you made any changes to the vacuum / intake system? Does your valve cover have the PVC on one side and the return to the carb on the other both hooked up? Some pics from the center of the engine to the right side showing all the lines might be helpful. Also, what's the oil pressure like?

 

[Hedgehog]

I don't believe it could be on the intake side OR the exhaust side. Either one and the engine simply won't run. It's got to be something inside the crank case. Blow by from bad rings is the usual culprit. Also the crank case needs to breath, if it can't breath the pressure has to go somewhere. The OP says that he has had two engines do the same thing. But, this isn't a common problem, at least not as severe as it is described. So, what might the OP be doing that creates the same problem with two separate engines? Is he getting a short block and swapping parts from one engine to the other, if so I would look at those parts.

 

[Bent]

Crazy! The only way oil gets to the top end is through the pushrods (unless you have one of the OLD motors with the shaft mounted rockers). Maybe the weep hole in one of your rocker arms is plugged and causing oil to spray. Maybe run it without the valve cover on for about 30 seconds to see what's going on.

 

[Peanut Butter]

Rings would be my guess. Improper ring gap, misalignment (did you stagger the gaps?), wrong size rings, maybe in wrong order. Just guesses. Rod

 

[Tinman22]

Given the amount of lust we all have for our aluminium valve covers and our ability too transfer them from engine too engine and never give them up once we have one I would assume you had this cover on the other engine as well. Oil running across the baffle as you describe is excessive. It sounds like this is where your problem might be. Who made the cover?

 

[2jeeps]

Hi everybody, I'm the OP on this thread. I've been having technical difficulty on this forum: this is the third profile I've set up, and I can't ever log back in: keep getting a message saying I'm using the wrong username/password.

When I fill out the form for a password reset, I get no response, and the email function here on the forum has been disabled. I'm hoping a moderator will contact me to help me out with this issue, because I'm reasonably sure that once I log out here, I'll be blocked out again, and I'm out of email addresses to use for new profiles.

Enough about that: I've felt really guilty about not responding to all of the helpful advice in this thread, and that is my main purpose tonight.

The good news: the engine is running great, no more smoke, leaks, or other issues. I think this thing has more torque than my wife's 4.0 fuel injected YJ, and its getting about the same mileage. I'm having a ball with it!

The bad news: I'm not really sure what fixed it!
To answer a few questions: I did change valve covers- the one that was on there was one I bought from Ebay, and the baffle design was slightly different than the one that came with the new engine. So, I went ahead and put the OTHER one on the engine, and hooked the PCV system back up. No issues, BUT my gut tells me the oil flinging was moderating itself prior to my having done that. (I know, that wasn't a very scientific way of going about it, but at that point, I just wanted my Jeep running!)

I think that perhaps there was some blow by from unseated rings which finally took care of itself once I had around a hundred miles on it, but I don't know for sure. I'd welcome opinions on that, but due to these technical difficulties, I can't guarantee I'll be able to respond. So I'll close by saying that I'll keep lurking on this forum even if I can't get back on, because its very helpful as well as fun, and by thanking all of you who responded to this thread.

rls120,bertha51,2jeeps (maybe the third time will be a charm!)