75' CJ5 w/ 304 Exhaust Tapping Noise and Low Compression Diagnosis Help - Page 2 - JeepForum.com
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post #16 of 20 Old 05-21-2020, 08:38 AM Thread Starter
PottsyCJ5
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Thanks for the info. I am starting to research what I need to do to pull the manifold and re-install it, as well as the heads. I will definitely keep an eye out for this.

As for the choke heat tube, I was not aware where the choke heat tube enters the manifold is actually exposed to anything. I thought there was just a closed pocket there based on what some other folks have said. My choke heat tube is pretty fragile at this point and I am afraid to touch it. When I rebuilt my carb and removed it, it got a small crack in it and I don't want to damage it further because I can't seem to find a replacement and I like the automatic choke. I am tempted to pop that open and take a look though.

As for the leak down test, I provided the results a few posts up. The results 100% pointed to something related to the exhaust valve. At TDC there was pretty much 100% loss of compression through the passenger side exhaust. To be sure, I cycled the engine and could hear the intake valve open and air come through the carb and then close. But no matter what position the cylinder stroke was in, air was coming out of the exhaust valve. So unless by some miraculous event this frees itself up, it looks like I need some head work done.

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post #17 of 20 Old 05-21-2020, 12:27 PM Thread Starter
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Okay I could use some advice here...

I just spoke to my CJ parts guy and he said he has two rebuilt heads for a 304 with all new valves and seals and wants $700 for the pair. He said they should be drop in and I would be able to use stock length push rods.

First is that a decent price in comparison to what it would cost to have a valve job done to my current heads?

Second, is there anything I am not thinking of that should make me shy away from replacing the heads as opposed to having a valve job done?

Finally, should I just pull the heads and try and clean it best I can, replace the valves and seals and call it good? I have no idea how well a shade tree mechanic could get a head without a machine shop.

Since this is the second valve issue I have had on this head I suspect they are all probably coming due for a valve job. If I purchase these, my plan would be to keep my existing heads and rebuild those in my spare time for potential use down the road. Again, my compression seems good and Iím not getting any smoke.

If I do replace the heads, my plan would be to inspect the cam and probably replace the lifters while Iím there but unless there is an obvious issue with the cam, leaving that alone. Iím not interested in anything more powerful than stock for now. I just want to get back to a reliable motor I can trust for decent length road trips in the oleí CJ5.


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post #18 of 20 Old 05-21-2020, 03:02 PM
pedal2themetai
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HI cam and lifters are usually replaced as a set.. if its all stock and the looks of that valley and heads it is most likely due for a new set and since your in there and have to remove them anyway to replace the cam maybe timing chain and gear set as well.
good luck
tim
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post #19 of 20 Old 05-22-2020, 11:29 AM Thread Starter
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Thanks Tim. Itís looking like my first step should be pull the intake manifold and see what I can from there and then if Iím doing heads potentially cam and lifters too. I wish this motor pulled this a few weeks before I decided to drop $800 on a new winch.


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post #20 of 20 Old 05-22-2020, 06:22 PM
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Since you are this far into it with 40 plus years under the engines belt, it's probably a good idea to rebuild the heads - period.

If you pull the heads, replace the cam & lifters, you will also want to replace the original nylon timing gear. You can check the slack in the chain to see if it is ok, but for $40, why risk it.

Sometimes there is a lot to the timing gear replacement if an aftermarket cam is used as the oil passage hole can be off set.

You can search for answers as you need them.

1972 CJ5 304 V8, 3 speed manual trans
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