Replacing Plastic Valve Cover on 81 CJ 258 -
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post #1 of 7 Old 06-18-2003, 04:54 PM Thread Starter
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Replacing Plastic Valve Cover on 81 CJ 258

I have a 1981 CJ, 6 cyc, 258. My old plastic valve cover is shot, I would love to replace with an aluminum cover. The problem is the aluminum covers need drilling and tapping. I haven't done much work on this jeep and I learning as I go. Should I stick with the plastic replacement or should I attempt to drill and tap?? Is this a really complicated procedure ?? I'm no mechanic, I've done work on the Jeep and other cars but this is getting a little out of my practical experience. Any suggestions or tips would be great.

Thanks for any suggestions or advice,

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post #2 of 7 Old 06-18-2003, 07:50 PM
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I'd like to second this question . 4WD Hardware has a new polished aluminum one for $89, and I'm dying to replace the leaky plastic one on my '85 model. I read on a post that came up in the search that it's just 2 holes that have to be drilled and tapped 1/2" deeper, so can anyone verify this? Also, please tell me one of them isn't the hole at the rear of the head against the firewall .


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post #3 of 7 Old 06-18-2003, 08:09 PM
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I put the Clifford aluminum cover on mine. I had to tap two holes in the head on the carburator side. They were already drilled or cast in the head and only had to be tapped (I think that they were originally locating holes or something like that). You'll need a tap that will cut all the way to the bottom of the hole as they aren't drilled very deep and if you try to drill them deeper you will drill into a water jacket. Don't ask me how I know that.

'86 CJ7, 258 w/Mopar MPI, 4.56 gears, rear Detroit/front Truetrac, full cage, OBA, 8274, 4" lift via Alcans/Rancho, 35's on beadlocks, other stuff. Built for rocks, mud is a four letter word.
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post #4 of 7 Old 06-18-2003, 09:34 PM Thread Starter
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I have an old 258 in my garage and I took off plastic cover and tried to fit aluminum cover. All seems to match except for the two hole on front and back of cover. These two holes did not match exactly but were really close. I tried to bolt down and it seems to work. I didn't try on my '81 yet but everything seems to match???
Would slightly forcing the two on the end cause any problems... it seems almost impossible to drill and tap since existing holes are so close to perfect fit????

Any thoughts????
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post #5 of 7 Old 06-18-2003, 10:06 PM
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It really helps if you know how to tap and have the tools. I did my buddies 83 and tapped the 2 holes on the carb side. I don't remember going deeper, just larger and using shorter bolts all the way around. It turned out real good with no leaks. A trick I use on my plastic one, is use the thick cork gasket and silicone/rtv on both sides and allow 24 hours before you drive it. Degrease the hell out of both the head and cover mating surfaces beforehand with brake cleaner (I have found Pyrol to be the best). If the sides of the plastic cover are really bowing out, it's time for a replacement and/or your engine may be running hotter than it should at times. Zor169, you may have a 4.0 aluminum cover as the bolts holes are different then the 258 type (and the aftermarket 258 covers)

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post #6 of 7 Old 06-18-2003, 10:12 PM Thread Starter
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Its 4.2 L cover.... its carved on the top of new valve cover.... unless someone out there is screwing with my head !!!!
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post #7 of 7 Old 06-18-2003, 10:43 PM
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Old topic. I used the Westside performance aluminium cover and it requires, NO DRILLING, NO TAPPING, NO GASKET. It dosent leak!!! Had mine on now for three years and all is well. Now time to get to that pesky rear main seal.
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