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JeepSaffer View Drop Down
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    Posted: 25 Sep. 2016 at 5:05pm
So before I start with my questions, a little history.

When I bought this jeep it was not in running condition and the engine could not be started for various reasons like no fuel pump etc.

I tested all cylinders and got good compression on each (lowest was 94 psi).
I worked to get it running and I eventually did so (after realising that the timing was off due to the oil pump not being indexed correctly). So I got it running and probably ran it for about a minute. It wouldn't idle, but it would rev. And there were no horrible noises, visible leaks or explosions.

Fast forward to where I am today. I have decided that there is no point in fixing something that isn't broken, so it has not been my intention to rebuild this engine although it is currently out of the jeep and on an engine stand. I have simply wanted to clean it and repaint it so that it will match the rest of the jeep when it is finished. I started stripping parts off it today, particularly wanting to get the timing cover off because the gasket was all mashed up and I wanted to replace that. This is what I found:




Yup, the gasket wasn't the only thing that was mashed up! The camshaft timing gear teeth are all mashed up too! 

So, my first questions: What would cause this? Is it common? Is it indicative of a bigger problem?

Having seen the problem above, I decided to go ahead and take the head off to take a look inside. This is how it looks:



Lots of carbon and scale, but no cracks or other obvious problems.





Again, lots of carbon, but no cracks. No obvious ridges in the cylinder bore that I can feel. 

So I realise I might be opening a whole can of worms here, but these are my questions:
Does all of this look normal for a head and block that has just been opened?
Given that I have good compression and this engine runs, should I just clean up the head, replace the timing gear and seal it all up again?
Is there anything that can be seen or checked now that it is open that I should be looking at?

As I said I don't believe that the engine should be rebuilt just because it is open, especially given the cost of doing so. But I would appreciate any advice on things I should be looking at or checking while it is open like this.

Thanks in advance,

Mike

P.S - Sorry for the sideways photos. I don't know why the forum upload rotates some of them. They look correct on my computer!
1948 CJ2A #204853 in South Africa
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Points: 3400 		Post Options Post Options   Thanks (0) Thanks(0)   Quote TERRY Quote  Post ReplyReply Direct Link To This Post Posted: 25 Sep. 2016 at 5:14pm
That gear is "fiber" and is fragile.
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Thanks Terry, i get that, but i didn't beat on it with a hammer. I opened the timing cover and found it like that.

My question is if there is something wrong with the engine that could have caused damage like that, that if i don't fix will do the same kind of damage to a replacement gear? Is there something i should be looking at other than simply replacing the gear?
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What does the steel gear look like? If it's all good, then i would just replace the fiber gear. 

I have to wonder if that damage was from sitting - where the teeth meshed and "became one" until the motor started moving again. Just a theory. 
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Yes, steel gear looks good.

I've also wondered about the fibre gear.... does it not go soft over time? I'm kinda thinking along the lines of super compressed cardboard here. If it sits in liquid long enough does it somehow lose its strength?

Come to think of it, anyone know why the gear is made from fibre in the first place? Seems a funny thing to make a gear from.....
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Replace the fibre gear and carry on. It looks like hone marks in the bore to me, so at some stage in the recent past the engine has been rebuilt.

I did put an alloy/steel gear set on my GMC 6x6, but its really not an option for a rough running four cylinder L-134, stay with a new fibre gear and it will run sweet.

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As long as it's open I'd be documenting at the least... measure the bores (or at least check the top of the pistons for oversize stampings), measure the head thickness to see if it's been planed, etc. drop a machinists straight edge across the head and deck in every direction

Check the valve seats (especially the exhaust), check the valve tappet clearances/perform a proper valve adjustment... your in there, you might as well.  If it were me I'd be pulling the valves to check guide clearance and spring length.  It's cheap piece of mind for me just to know.

FWIW, plastigage is cheap... you can get a decent sense of things on the bottom end in the span of a beer or two by dropping the rod and main caps (one at a time) and checking for scoring and clearance...  If nothing else having as much info as you can when you close it up will help you gage where you're at-

You say your lowest cylinder compression was 94... were the other three in that ball park, or did you have three at 110, and one at 94?




Edited by mbullism - 25 Sep. 2016 at 8:05pm
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Thanks all, especially Mbullism, for the pointers.

Seems the current feeling is to replace the fibre gear, check a few things, measure a few things, and close up again.

My compression readings were as follows:
No 1: 104 psi
No 2: 116 psi
No 3: 101 psi
No 4: 94 psi

Does this tell us anything new?

Mike
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Sometimes a backfire will wreck a fiber gear. Yours looks simply deteriorated. The black indicates too rich a mixture from the carb. The rest looks normal to me. A new fiber gear, clean her up and tune/kit the carb. You should be good to go. John
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Thanks John, and good to hear from you again.

Regarding the carbon buildup, i have three options:
1. Leave as is, because all engines look like this inside
2. Clean using some kind of solvent (what?)
3. Clean mechanically somehow

Any suggestions?
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Don't get crazy with a tool and drill or die grinder. You can damage the valves. I'd just clean the surface the head gasket seals on with a hand scotchbrite pad and solvent. Mechanics use the die grinder scotchbrite pads, but judicious use is needed because they will actually move metal too! A old trick to clean carbon out is to bring the engine up to a nice smooth fast idle at operating temperatures.  Take a soup can and poke a small "drip hole " and slowly drip water in with the gas. It will clean all the carbon out of the cylinders. I'd also recommend getting one of the copper head gaskets. I like the way they "feel" when you go back and re-torque the head. Otherwise a double sided fiber gasket works well too, but not the steel sided one. Make sure you allign the timing marks between the steel crank/cam gears. one tooth off they will run,  But not well. John
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The so called fiber gears are made from a material called Micarta its so tough billiard balls and bowling balls are made from it. Its a Phenolic Resin with a cloth sub straight. They make bearings for the prop shafts on ships out of it.
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Originally posted by JeepSaffer JeepSaffer wrote:


My compression readings were as follows:
No 1: 104 psi
No 2: 116 psi
No 3: 101 psi
No 4: 94 psi

Ideally you'd like to see all 4 within maybe 10% of each other...15% on the outside.  All things being equal everything should wear in together relatively equally.  The high and the low stand out a little.  Under load the higher cylinders will be carrying the 94 to a degree... (I'd almost rather they were all in the 94-95 range, but it'll go as is.)

At the time, a few squirts of oil and a retest could have helped sort out rings vs. valves or head gasket... obviously the head gasket is a non issue so long as the mating surfaces are decent at re-assembly.  If the gasket was at issue, reassembling should yield different results.  A cracked head, burnt or bent valve or seat or a weak valve spring left unchecked will likely result in similar results.

If reassembly is in the works, I'd give everything associated with the low cylinder a little extra scrutiny.  You may find nothing without going a bit further.  Give that bore a really decent look over for even subtle vertical scoring in case you're carrying a broken ring.

If you find nothing obvious, retest the compression afterwards and if that cylinder comes up with a squirt of oil you may have a ring issue there.  It would be odd for one bore to wear so differently.

In the end, over 50-70 years there's no telling what shadetree mechanics have or haven't done... People DO replace single valves, or re-ring single pistons.  These things WERE sold as tractors, and they aren't exactly high rpm indy car engines-

.02




Edited by mbullism - 27 Sep. 2016 at 2:08pm
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Thank you, I really appreciate your advice and learning as I go along.

I'll complete the picture for you more fully: 

When I originally tested the compression, I found NO compression on cylinder #4. I pulled the manifolds and the valve cover and found the #4 exhaust valve was stuck open. Hence no compression... 

I oiled it with ATF over a few days and eventually got it moving and then it came free and started moving on it's own. That's when I re-did the test and got the results mentioned above.

So, I kinda think that the lower compression is a remnant of the valve being stuck or still not seating as well as it should. In which case is it a good idea to pull this valve and guide, clean them both up, and reinstall them? I could test the spring at the same time... Or is it a case of "if you mess with one you have to do them all"? The objective would be to get this #4 E valve to seat a little better to hopefully get up into the 108-110 psi compression range and more closely match the others.

Thoughts?
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