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  #1  
Old 05-20-2021, 01:32 PM
mwood65's Avatar
mwood65 mwood65 is offline
258 I6
 
Join Date: Jul 17, 2017
Location: Payson Arizona
Posts: 428
Valve cover

I don't know if this post is for help, or just to vent my anger/confusion.


I have the 74' Cherokee with the 258, Steel valve cover and it leaked fairly bad so I changed the gasket.


1st time I changed it, it still leaked.
2nd time I changed it, it leaked.
3rd time, it leaked.


Bought a Clifford 6=8 aluminum cover from a member on here
and installed it, It doesn't just leak it POURS out.


It's not like I haven't changed valve cover gaskets before, probably done 2-3 dozen in my life with no problems. Installed correctly and tightened to the correct torque.


Both surfaces clean and scrubbed both head & cover with brake kleen to make sure they had no oil so the rtv would stick good.


I am ready to sell the Jeep over a damn valve cover gasket because I am so frustrated!!!!


There, I vented, If anyone has any idea's feel free to shout at me.


My Uncle said to try 2 gaskets but that sounds silly and I have never heard of that before.
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  #2  
Old 05-20-2021, 04:19 PM
MysticRob MysticRob is offline
327 Rambler
 
Join Date: Nov 26, 2019
Location: Boise, ID
Posts: 589
My Dad the 40+ year mechanic always told me to hammer the entire sealing surface of the valve cover, tranny/oil pans, etc, on an edge of some sort to ensure the entire lip of the cover is flat.
What happens is when covers get torqued repeatedly over the years, the sealing surface around the bolt holes gets smashed and depressed lower into the surface it's sealing against, so everything else not close to the bolt holes will still be raised far above the surface, hence the reason yours likely leaks, even with good gaskets.
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1988 Jeep Grand Wagoneer / Baltic Blue & Tan
2008 BMW 535xi Wagon / Deep Sea Blue & Tan

My build thread:
https://ifsja.org/forums/vb/showthread.php?t=189245
My Howell TBI Install How-To:
https://ifsja.org/forums/vb/showthread.php?t=189877
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  #3  
Old 05-20-2021, 08:47 PM
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mwood65 mwood65 is offline
258 I6
 
Join Date: Jul 17, 2017
Location: Payson Arizona
Posts: 428
Quote:
Originally Posted by MysticRob
My Dad the 40+ year mechanic always told me to hammer the entire sealing surface of the valve cover, tranny/oil pans, etc, on an edge of some sort to ensure the entire lip of the cover is flat.
What happens is when covers get torqued repeatedly over the years, the sealing surface around the bolt holes gets smashed and depressed lower into the surface it's sealing against, so everything else not close to the bolt holes will still be raised far above the surface, hence the reason yours likely leaks, even with good gaskets.






Sorry I forgot to mention I did that and even checked it with a straight edge, it's flat.
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Old 05-20-2021, 09:17 PM
MysticRob MysticRob is offline
327 Rambler
 
Join Date: Nov 26, 2019
Location: Boise, ID
Posts: 589
Well if you're sure both valve covers are nice and straight, it must be the gasket or head.
Is it leaking consistently in the same spot?
If not it could be cursed. Maybe a priest?
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--Rob--
1988 Jeep Grand Wagoneer / Baltic Blue & Tan
2008 BMW 535xi Wagon / Deep Sea Blue & Tan

My build thread:
https://ifsja.org/forums/vb/showthread.php?t=189245
My Howell TBI Install How-To:
https://ifsja.org/forums/vb/showthread.php?t=189877
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  #5  
Old 05-21-2021, 01:20 PM
inkedmonkey inkedmonkey is offline
232 I6
 
Join Date: Feb 12, 2021
Location: Kansas City, Mo
Posts: 156
I fought and fought the Offenhauser valve cover on the 250 straight six in my 52 GMC. Ended up installing studs and then used some Non hardening gasket maker on each side of a cork gasket. All sealed up for a couple thousand miles now.
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  #6  
Old 05-25-2021, 06:02 PM
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Cliff Cliff is offline
350 Buick
 
Join Date: Mar 30, 2002
Location: Upper East Tennessee
Posts: 775
Two gaskets sounds like twice the possible places to leak.

I always use rubber over cork. Not sure if you tried both. But others like cork.

Try studs and a spreader (I think they call them "hold downs") under the nut. Moroso has them on their web site under "valve cover accessories." Mr. Gasket used to have them too. They spread out the torque from the stud 2" in both directions.

Rough up the contact surface of both the head and the valve cover. The head is likely slick from years of sealant. Take a file or rough sandpaper and restore the factory roughness of cast iron. On the valve cover, roughing surface will remove old sealant and give new sealant a better surface to adhere too. Go slow and be careful. Use a vacuum while you do the heads to keep debris out of the motor.

Look at your sealant options as there are new products out there. Can't vouch for any new products but good ole Permatex #2 has always been my favorite.

Call tech support at Edelbrock. I bet they help you even though it's not their product.
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  #7  
Old 05-28-2021, 06:57 AM
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tgreese tgreese is offline
 
Join Date: May 29, 2003
Location: Medford MA USA
Posts: 11,460
I have owned two 258s, each with the steel valve cover.The plastic cover is much worse this way.

The first was a brand-new 1975 CJ-6. From the factory, the valve cover leaked. Not bad - no drip - but enough to the side of the engine was covered with a grease spot and steadily increasing layer of oily dirt.

The second is my J10, which leaked when it came to me. I replaced the gasket with a new Felpro rubber (?) gasket and it does not leak now. Did not do anything heroic. Cleaned both surfaces down to clean and oil-free iron/steel. Straightened the valve cover flange with a flat dolly and little ball-peen hammer, especially around the bolt holes. Glued the gasket into the cover with weatherstrip cement and let dry. Sparingly used black RTV between the gasket and head and assembled with a palm ratchet. No leaks so far.

Comments - I think this is a problem with all OHV inline sixes. The long valve cover is hard to seal. Made worse by how the cover weaves in and out to match the head surface.

Felpro gaskets are good, but it appears that they have discontinued the all-rubber gasket type and replaced it with a cork-rubber composite. The rubber type is what the factory used. IME the all-cork gaskets tend to shrink as they sit on the shelf, so you could get a bad one.

Glueing the gasket into the cover helps to hold it in place as you mount it on the head. I use the 3M weatehrstrip cement, but there are gasket cements you could use.

The cover tends to distort in particular around the bolt holes. This comes from over-tightening to try to stop a leak, typically. The factory spec is really low, like 40 INCH-lbs. I use a palm ratchet, but a nut driver works too. Not an issue as long as you do not overtighten. Suggest you use a similar tool and tighten in an alternating pattern until you see the gasket cement start to ooze out of the joint, and no further.
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Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination ATs, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
ECO Green: '15 FCA Jeep Cherokee KL Trailhawk
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