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Valve adjustment on cj2a and cj3a

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samned View Drop Down
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    Posted: 11 Aug. 2007 at 9:38pm
Is the valve adjustment spec the same on the cj2a and the cj3a?
 
The manual I have says .016 gap at room temperature for the Cj2a.
 
Is it the same on the cj3a?
 
Any help would be appreiciated
 
Thanks
Samned
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GalenHorton Quote  Post ReplyReply Direct Link To This Post Posted: 11 Aug. 2007 at 9:55pm
Fellas, tell me if I'm wrong, but I would say that the gap would be the same, as long as you're talking about a L-Head engine.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Militoy Quote  Post ReplyReply Direct Link To This Post Posted: 12 Aug. 2007 at 1:24am
Same basic engine - same valve clearance. I always set them in the morning - dead cold.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote samned Quote  Post ReplyReply Direct Link To This Post Posted: 13 Aug. 2007 at 11:33pm
Well I adjusted the valves. and boy did I screw that up. The compression went from 120 to 80 in cylinders 1,2 and 4. The #3 cylinder had 80 psi to start with and it did not help.
 
I still have a pecking noise, and I friend of mine said it was probably the valves.
 
Could the valves being out of adjustment make this noise ?
I am going to have to go back and try it again.
 
Does anybody have any advice?
 
Any helpp would be greatly appreiciated
 
Thanks
Samned
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CJ3A Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug. 2007 at 8:15am
Valve adjustment is different on chain driven (.014) and gear drive engines (.016). If you have a chain drive engine that you are adjusting to .016, then you might have that drop in PSI.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Militoy Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug. 2007 at 10:35am
Originally posted by CJ3A CJ3A wrote:

Valve adjustment is different on chain driven (.014) and gear drive engines (.016). If you have a chain drive engine that you are adjusting to .016, then you might have that drop in PSI.
 
I've always followed the practice of setting both exhaust and intake valves (cold) at .016, for all my engines from early MB (chain-driven) to fiber gear-driven M38 and CJ3A models. A looser clearance shouldn't cause a drop in compression (since the valve opens only when the clearance drops to zero on the cam lobe) - but it might prevent a burned exhaust valve. The Universal Manual does point out the difference between the flywheel timing marks on pre-175402 CJ2A engines and the later CJ2A and CJ3A engines - but it specifies .016 for both types. I have seen references to the .014 clearance - but the later references in my collection seem to "correct" the number to .016 for all engines.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sean Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug. 2007 at 11:50am
Valve lash is specified at .014" in all MB & CJ2A manuals through at least 1947, and .014" is cast into every head through at least 1948 (I think it's cast into all 640161 CJ2A/3A castings).

Why they chose to increase it to .016" in later manuals is a mystery to me.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote CJ3A Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug. 2007 at 12:15pm
Originally posted by Militoy Militoy wrote:

A looser clearance shouldn't cause a drop in compression (since the valve opens only when the clearance drops to zero on the cam lobe) - but it might prevent a burned exhaust valve.


You are absolutely correct! I stand corrected
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Militoy Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug. 2007 at 12:40pm
Originally posted by sean sean wrote:

Valve lash is specified at .014" in all MB & CJ2A manuals through at least 1947, and .014" is cast into every head through at least 1948 (I think it's cast into all 640161 CJ2A/3A castings).

Why they chose to increase it to .016" in later manuals is a mystery to me.

Sean
 
I believe you're right on the 640161 castings - both the early (non-ribbed) and late models I've seen are marked .014. Sometime in late '49 or early '50, the 3A's started coming with the 800376 head, and the M38's came with the 641087, and later 804380 heads - which are marked .016 for both exhaust and intake.
 
As to why they switched to .016 on both the heads and in the manuals (Carter carb tuneup sheets also switched for all engines around that time) - my guess is that they had some trouble with burned exhaust valves, as a result of mechanics setting at .014 with the engine too warm. Much easier to change specs on both exhaust and intake clearances to avoid confusion - and to put up with a little valve rattle during warmup, rather than risking burned valves.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote samned Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug. 2007 at 8:09pm
The engine in the jeep has the valve claerances cast into the head and they are .14
 
If the block is a cj2a or 3a, would the .14 head make a difference in the valve adjustment?
 
If the manual is calling for .16 and the head is .14 which should I go with?
 
 
Thanks
Samned
 


Edited by samned - 14 Aug. 2007 at 8:10pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sean Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug. 2007 at 8:23pm
Originally posted by Militoy Militoy wrote:

- my guess is that they had some trouble with burned exhaust valves, as a result of mechanics setting at .014 with the engine too warm.
That would give you more clearance when cold, making burned valves less likely.

It doesn't help that Willys manuals are contradictory to the head casting, calling for hot or cold:

    

    

    

Sean
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Militoy Quote  Post ReplyReply Direct Link To This Post Posted: 15 Aug. 2007 at 4:18pm
Originally posted by sean sean wrote:

...That would give you more clearance when cold, making burned valves less likely.

It doesn't help that Willys manuals are contradictory to the head casting, calling for hot or cold:

    

    

    

Sean
 
That makes sense - I can see my logic was "inverted" (must have been tired). So adjusting at .016 HOT might give you a little more rattle than you might want when the engine cooled - but adjusting to .014 COLD might have cut the clearance too tight when the engine heated up. Maybe the valves "grew" a little more with temperature than Willys figured on paper - or maybe a lot of mechanics adjusted valves when it was Really cold.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote samned Quote  Post ReplyReply Direct Link To This Post Posted: 19 Aug. 2007 at 11:26pm
I amready to scream !!!
 
I have adjusted the valves on my jeep engine to .016 cold for the 3rd time. After start up I shut the engine down and the clearances are not consistent. I had one go to .022 and another to .014. Am I missing soemthing. I am placing one wrench on the tappet and one on the adjusting nut. I then turn to the proper clearance. Is there a locking nut I am missing, or what could be the cause of this problem.
 
Any help would be appreciated.
 
Thanks
Samned
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GaryArf Quote  Post ReplyReply Direct Link To This Post Posted: 20 Aug. 2007 at 6:42am
Samned,
I know your frustration. I've adjusted valves all weekend and finnally got it right. I did it using two feeler guages ( the professional type that have a 45 degree bend)  one at .015 and one at .017. adjust first with the .015 then try the .017 adjust till it barely goes in then back off so very little till it won't. then go back  and check it with a .016.
 Don't use a multipule stacking guage as your accuracy will be compromised. when you think you got it, go back and do it again... you will find you will need to readjust again. test yet again and it should be good.
  Oh, and without the manifold off it will be even harder.
Good Luck.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sean Quote  Post ReplyReply Direct Link To This Post Posted: 20 Aug. 2007 at 12:41pm
Quote ... I had one go to .022 and another to .014. Am I missing something.
Perhaps.  Is this a new rebuild, or an engine w/many miles on it?  Is this change in gap measured while the engine is still hot, or after it has cooled down?

If it has much mileage on it, there are points of normal wear that will cause the changes you're seeing.

Valve stem end to tappet adjuster:  when new, these are both flat and mate evenly.  After many miles, the valve stem end beats a concavity in the tappet adjuster, and you can no longer get a correct & consistent gap.  Can be fixed by having a shop dress the valve stems & tappet adjusters back to flat.

Cam lobe to tappet face:  due to wear, the cam lobes may no longer be perfectly circular and/or the tappet faces may not be flat.  Would require dressing the tappets and/or regrinding the cam.

On your valve that's coming out .022", try turning the crank by just  few degrees at a time.  If the gap changes at different points, find the largest gap, and adjust it there (assuming that the total difference is only a few thousandths).  If you find a difference on the order of .010 or more, you've got major wear somewhere.

Sean
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Post Options Post Options   Thanks (0) Thanks(0)   Quote samned Quote  Post ReplyReply Direct Link To This Post Posted: 20 Aug. 2007 at 9:57pm
The motor is from a Willys Mb. It runs good and does not smoke. I guess I will try to pull the engine and look at it out of the Jeep.
 
It is really frustrating.
Thanks for the help
 
Samned
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brachus12 Quote  Post ReplyReply Direct Link To This Post Posted: 25 Aug. 2007 at 2:41pm
Is there anything that walks you thru this procedure? I'm an auto newbie and am not sure how to tell when the camshaft lobe is on its heel on an assembled engine.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote GaryArf Quote  Post ReplyReply Direct Link To This Post Posted: 26 Aug. 2007 at 7:27am
On a L head you can tell for sure which one to adjust if the other valve in that cylinder is up (exhaust or intake) than the one that is down can be adjusted.
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