valve cover UNDERPRESSURE!!!!!!!!!!!!

A

allabs5150

New member
1050659

Last night I went to add oil to my 79CJ 258ci. While the Jeep was running I unscrewed the oil filler cap and a sound of air underpresssure came out of the valve cover.......(sorta like shaking a bottle of soda up and unscrewing the cap)....the engine also started to idel down almost to stalling....any ideas??????????????



Just put a brand new Weber on it a week and a half ago which does away with alot of the factory vacuum lines...could this possibly have anything to do with it????also noticed the valve cover started leaking badly after the carb install....could the Weber be putting alot more pressure back into the crank case?????? ....which might cause gasket failure around the valve cover, or any other areas?????



Any ideas???????Help before this thing makes me nuts
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[addsig]
 

1050661

Did you check the PCV valve and filter?[addsig]
 
1050663

or it could be blow by real bad blow by from the way it sounds my be time for a head job to valve seals sound shot.



marc[addsig]
 

1050677

Make sure the PCV system is working correctly, in the correct direction. Crankcase gases should be sucked into the carb for burning in the engine, and the crankcase should draw fresh air through the air intake somewhere. If the engine is burning those crankcase gases, they may be building up in the engine. This pressure is why the valve cover gasket is shot. Sounds like a mess, good luck.[addsig]
 
1050679

Ya I been thinking qabout it and was wondering if the PVC was ok.......I replaced it when I put the Weber on, but I may have it on wrong of it could be faulty..

Thanks for the advive....gonna rip into it tonight UUUUGGGHHHH[addsig]
 

1050681

Oh ya and one other thing, a few of you guys mentioned valve seals and piston rings.....i dont doubt you knowledge but as far as my wallet goes I hope your not right, wouldnt I have experienced this problem sooner, or is it just a coincidence that it all happend after the new carb install???



Just the reason I am thinkin something with the vacuum lines or PVC is not right, none of these problems surfaced till the Weber was installed[addsig]
 
1050686

I just installed a weber a couple of days ago. First make sure you have the PVC valve in the front of your valve cover (toward the radiator). I noticed that the hoses that came with my carb were kinked and one had something in it. It may be block. I also instead of hooking the intake breather (on the rear of the Valve cover) to the air filter on the carb. Ijust went and bought a chrome breather by itself and popped it right in. It give in more air and also eliminates more hoses. I am also in the process of doing the nutter bypass to eliminate the computer. Make sure you have the timing right. [addsig]
 

1050688

Yeah, this is sounding like your PCV tubes arent installed properly to your weber.

Just for reference, the hose at the back is supposed to go to the air filter to draw air into the valve cover area, and at the front is where the PCV valve goes out of the engine.

It doesnt sound like the PCV valve at the front is the issue, as you said you have a negative pressure in your valve cover. I would pay more attention to the hose at the back of the valve cover. If i remember correctly I believe it plugs into the bottom corner of the air filter on the Weber carb. Check the install manual to be sure.[addsig]
 
1050690

<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font class="pn-sub">Quote:</font><HR></TD></TR><TR><TD><FONT class="pn-sub"><BLOCKQUOTE>I also instead of hooking the intake breather (on the rear of the Valve cover) to the air filter on the carb. Ijust went and bought a chrome breather by itself and popped it right in. It give in more air and also eliminates more hoses. </BLOCKQUOTE></FONT></TD></TR><TR><TD><HR></TD></TR></TABLE>



Hmm... you know, thats not a bad idea, i'll have to try that on mine. Did you just pop it into the top where the grommet is, or did you rig up an adaptor?

Also, can you tell me who makes the breather and possibly part number, size, etc?[addsig]
 
1050693

chinard

I picked up the breather at Autozone. It just popped right into the grommet. Mine was 3/4 neck fit. It is made by Spectre - Universal push in breather. They have different sizes and colors. P/N #4300[addsig]
 

1050707

<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font class="pn-sub">Quote:</font><HR></TD></TR><TR><TD><FONT class="pn-sub"><BLOCKQUOTE>I just installed a weber a couple of days ago. First make sure you have the PVC valve in the front of your valve cover (toward the radiator). I noticed that the hoses that came with my carb were kinked and one had something in it. It may be block. I also instead of hooking the intake breather (on the rear of the Valve cover) to the air filter on the carb. Ijust went and bought a chrome breather by itself and popped it right in. It give in more air and also eliminates more hoses. I am also in the process of doing the nutter bypass to eliminate the computer. Make sure you have the timing right. </BLOCKQUOTE></FONT></TD></TR><TR><TD><HR></TD></TR></TABLE>



Jay thanks for the advice.....The universal air breather you plugged into your valve cover sounds like a great idea....but in doing this did you have to plug the connection on the back of the weber where the hose would have went ????????? or is it just left open????????????[addsig]
 
1050714

The breather was supposed to go to the air cleaner not the carb. I just cover the hole in the bottom of the air filter plate. The PVC valve is supposed to go to the port that you screwed into the adapter plates. I have my PVC valve going to that port with a tee connection and the other end goes into the evaporator canister under my washer fluid bottle.[addsig]
 
1050789

My .02 worth. Alot of this advice is correct. You need to make sure that the PCV system is working right. The PCV valve should rattle when shaken and it must be the right one for your application. Also check the hose for kinks or blockage. As a rule if it is valve seals you should notice blue smoke from the tail pipe. If all checks out here do a compression test. If the PCV valve or hose is blocked the hose going to the air cleaner should have oil in it as the oil would have no where else to go except through the valve cover gasket. Hope this helps.[addsig]
 

1050938

Well I went through the hole vacuum system with a very good friend of mine who is a top rate mechanic. Seems as though i did have everything set up correct but in the process of converting over to the Weber, I decided to replace all the 23 year old grommets and such......well for some reason this engine has some major blow by and by sealing up everything with new tight grommets it just couldnt breath. so i took Jay89's advice and pulled the rear vacuum hose that goes to the air filter on the carb and popped in a universal breather...all is now well, for the time being anyway. My only concern is how much if any damage it may have caused the engine, I know putting all that pressure back into the crankcase isnt good on rings, valves, bearings. so Iam concernd.....thinkin about lookin for a 4.0 or possible doing a V-8 conversion. Any ideas on which would be easier on the wallet????? Ido have access to a late 1960's chevy 327 complete just need to be freshend up. i guess a 327 and 350 would bolt up the same[addsig]
 
1050988

Good luck on your motor. It sounds like a tired six cylinder to me. I had an 80 CJ with the 258. The breather on top of valve cover that went into the stock air cleaner assembly filled the air cleaner with oil. I piped my breather tube to the bottom of my Jeep. The oil/gas blowby slowly dripped out. If your crankcase can't breathe you will blow out your gaskets. My fix was cheap and I got more mileage out of my air cleaners. It really needed a rebuild though![addsig]
 
1051014

I would say go with the v8 conversion. Either way its not going to be cheap, but at least chevy v8's are a dime a dozen so to speak. And since you have a carb to begin with it makes it a lot easier as well. Swapping in a v8 carb wouldn't be too hard since you wouldn't have the modern electronics to mess with. But, EFI is nice when the going gets steep since it doesn't starve for fuel like a carb motor sometimes will. But either way, I would agree that it sounds like a tired out motor....



Sorry, this isn't what you had hoped to hear, but having V8 power would be nice.....[addsig]
 
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