1985 Jeep CJ7 compression

  • 1985 JEEP CJ7
Engine Mechanical problem
1985 Jeep CJ7 6 cyl Four Wheel Drive Manual

What is the normal compression reading for a 1985 jeep 4.2
Do you
have the same problem?
Saturday, May 1st, 2010 AT 8:14 AM

1 Reply

See my profile and other CJ5/7 POSTS! I sent this to you not long after your question arrived, I sent it "PM" in hopes that someone else would have "EXACT" figures you were after.

I went back and copied the "PM" and submitting it to you now, maybe it will help some, even though it is "Late" coming to you.

See my profile, AND CJ 5 and CJ 7 Questions, for my "Abilities". I answer alot of the CJ stuff, I am currently working on the '85 CJ 7 Stalls when hot.

I do not have exact numbers for you (searched my books cannot find) I left your question alone in forum, in case someone did have it.

I chose to rebuild a second engine, while still driving the original. Then I did a "quick" 6 hour "swap out", thus keeping all pieces, together and familiar...no confusion or problems, during the change-out!

I now have a 1976 "AMC HORNET" 258 in mine (same block and head, as all AMC, those years). When I built it, I put on the Jeep oil pan, and changed the cam (from a 1 barrel [YF carb] cam, to a 2 barrel [BBD carb] cam). Replaced the intake and exaust for a 2 barrel BBD CARB.

What I have NOW, with these changes is a "1979 Jeep 258 Engine w/2 barrel Carb......that was 6 years ago, since then I tried a WEBER DGEV on that intake, then Switched to a "Offy" 4 barrel intake, with a "HOLLEY" 390 CFM CARB (I like it alot)

Mine has the Stamped Metal valve cover (earlier 258s) and the head was drilled and tapped for this....later they (AMC) changed to a Plastic cover (anchors for valve cover, not great, leaks alot) They have aftermarket improvements for these later models!

I believe Displacement and that sorta thing, should be the same between both of our engines.

To sorta maybe help on your question, I tested COMPRESSION on my freshly rebuilt engine at 3000 miles after rebuild (6 or so years ago, wanted rings to be somewhat, broke in.)I had 135-140 PSI on each cylinder. I was told if they were ALL within 10-15 PSI of the HIGHEST reading, This was "ACCEPTABLE"......I am no expert on Engine Quality Specs, and cannot find a factory spec to your question. Seems like every guy out there has his own "Standards" on Quality! I was happy, mine were within 5 PSI of the highest PSI!

If you want to ask me a question or Reply, Try to respond to this "PM"

If you want, this next stuff may interest you!

Send me your Email Address, here in Private MessageI let you view my Walmart Albums----My JEEP MODIFICATIONS (not typical stuff)might wind up in spam

SUBJECT--look for wifes name "Denise Nelson"---OR---JEEPJEEPJEEPJEEPJEEP/ I WOULD LIKE TO SHARE PICS................or SIMILAR to this!

Read captions----will send mutiple albums (6 or more)library should get you to albumssee if there is anything you like or can usereply back here or at "PM" beside my '46 WILLYS AVATAR, in my answer. I can POSSIBLY assist you with other problems, you might have with your Jeep.

Love, Turddog


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Sunday, May 9th, 2010 AT 6:46 PM

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