Low Compression on Rebuilt Engine | Dodge WC-63

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Huntdog2003
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Low Compression on Rebuilt Engine | Dodge WC-63

Post by Huntdog2003 » Fri Jul 31, 2020 7:44 pm

Hello everyone,
I am hoping that someone can help me out with some issues that I am having with my Dodge WC-63 engine.

I recently purchased the Dodge from an older gentleman who had been in the process of restoring it with a friend before his friend passed away. The vehicle was probably 3/4 of the way through a full frame-off restoration, and was almost through the process of being completely reassembled when I purchased it. As a part of the restoration process, the engine had been completely rebuilt by an engine shop near where he lived and has been sitting in it's rebuilt condition for a few years without being run while the rest of the restoration was being completed.

After purchasing the vehicle, I started it up for the very first time since it has been rebuilt, and it was only running on 5 cylinders and would sometimes drop to only 4. After ensuring that my timing was correct, carb was adjusted correctly, and was getting spark to each cylinder, and did a dry compression test on each of the cylinders with the following results.

cyl 1: 100
cyl 2: 95
cyl 3: 95
cyl 4: 100
cyl 5: 60
cyl 6: 0 (the needle did not even twitch)

Now, I am 16 and have never worked on anything mechanical before this project, but from my basic understanding these are the potential issues that come to mind for a freshly rebuilt engine with no compression. 1. There could be a leak in the head gasket between cylinders 5 and 6 (but why would cyl 5 be at 60 and cyl 6 be at 0?). or 2. There is an issue with the valves not sealing (explains 0 on number 6) and some other problem with cylinder 5? My best next step to me seems to be pulling the head off of the engine to further asses what is going on. Does anyone have any suggestions as to what my issue could be and possible solutions? Should I go ahead and take the head off?

Thanks in Advance
-Hunter
-Hunter R.
1942 Ford GPW
1943 Dodge WC-63

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Bill H.
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Re: Low Compression on Rebuilt Engine | Dodge WC-63

Post by Bill H. » Fri Jul 31, 2020 8:20 pm

Welcome Hunter!

I think I would check the valve lash to make sure it doesn't have an issue there. It is possible, although not likely, it has broken rings on 5 and 6.

Because of valve positioning between 5 and 6 if it had a blown gasket it may not equal out. I doubt it's a gasket because you would still get compression on each cylinder, albeit it much less than the other 4.
Bill H.

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1962 AMC M422A1
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Re: Low Compression on Rebuilt Engine | Dodge WC-63

Post by Huntdog2003 » Fri Jul 31, 2020 8:59 pm

Thanks Bill,
Valve lash will definitely be first on my list of things to work on when I make it to the shop tomorrow! I can definitely see how a valve issue would cause 0 compression on cylinder 6, but I am still wondering about cylinder 5. Is it possible to have incorrect valve lash and still get 60 psi for that cylinder, or will it always cause the compression to be 0?
I appreciate your patience as this is all a new experience for me! I may understand many of the mechanical concepts in these vehicles, but I definitely have a lot to learn when it comes to working on them!
-Hunter R.
1942 Ford GPW
1943 Dodge WC-63

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Re: Low Compression on Rebuilt Engine | Dodge WC-63

Post by Bill H. » Fri Jul 31, 2020 9:32 pm

That would all depend on how far out of adjustment they are if any. Also, a valve stuck open will cause no compression. Do you hear any popping, hissing or sucking?

Try this little trick:

While the engine is running at idle hold a piece of paper up close to the exhaust pipe tip. If it's a valve the paper will noticeably try to suck back to the exhaust tip periodically. If the valves are good it will constantly blow away from the exhaust tip.
Bill H.

Welfare, a modern day career choice.

1962 AMC M422A1
1965 Stevens M416B1

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Re: Low Compression on Rebuilt Engine | Dodge WC-63

Post by parker007 » Fri Jul 31, 2020 10:21 pm

stuck valve from sitting. if 0 compression it full open always.

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Re: Low Compression on Rebuilt Engine | Dodge WC-63

Post by mdainsd » Sat Aug 01, 2020 8:31 am

ditto! i had a government rebuilt M37 motor, never run, but been in a can for 20 years. two valves really stuck. head off, lots of soaking with MMO. tip: do Not hammer on the valves to free them. take the head of and watch the valves while hitting the starter. report back.
52 M38 2X, '52 M37, '44 WC51, '42 WC 56/57, '50 CJ-V35(U), '42 GPW, '44 M3A1 Scout Car, 2010 M-Gator

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Re: Low Compression on Rebuilt Engine | Dodge WC-63

Post by Huntdog2003 » Mon Aug 03, 2020 7:51 am

Thanks for the tips everyone! I was able to get out to the shop the other night to take off the valve cover and watch the valves in operation. It seems that all of the valves are moving freely and without issues, however I did not have feeler gauge on hand to see if they are adjusted correctly. I will say that it does appear that both of the valves on cylinder 6 seem to rest all the way in their lowest position on the compression stroke, however until I make it back out with a gauge I can't say whether they are adjusted right or not.
-Hunter R.
1942 Ford GPW
1943 Dodge WC-63

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Re: Low Compression on Rebuilt Engine | Dodge WC-63

Post by motto » Tue Aug 04, 2020 5:40 am

It is possible though not very likely that you have a broken valve spring on No 6. That may also be the reason for the lower compression on No 5. Cylinder. Blowback into the manifold past a faulty valve will tend to upset the breathing of adjacent cylinders.

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Re: Low Compression on Rebuilt Engine | Dodge WC-63

Post by IvorGPW » Tue Aug 04, 2020 8:14 am

I had this same issue on my MB. It turned out the previous owner had installed new valve guides which had been installed but not properly reamed so when the engine heated up the first exhaust valve galled and seized in the up position. As was mentioned above it could be from sitting for awhile and hopefully that is the case. Incidentally I was around your age when this issue occurred on my MB and I didn’t have much mechanical knowledge but these are great vehicles to learn on.
Tate Christensen
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Re: Low Compression on Rebuilt Engine | Dodge WC-63

Post by Huntdog2003 » Wed Aug 05, 2020 7:44 am

Update:
I went out to work on the Dodge yesterday with a friend who has a little experience working on old tractor engines. One of the things that we noticed was that the head stud on the driver’s side rear had a nut on it, but the nut was sitting on the stud about 1/2 an inch off of the head. After feeling around that rear corner where the head meets the block, I noticed that the engine was slightly damp with what I think smelled like coolant. I also found another head nut that was not tightened down and could be removed by finger pressure. Apparently whatever shop rebuilt the engine did not do a very good job, so it looks like I will be draining the coolant, removing the head, replacing the head gasket and studs, and trying to figure out what exactly is wrong from there.
-Hunter R.
1942 Ford GPW
1943 Dodge WC-63

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Re: Low Compression on Rebuilt Engine | Dodge WC-63

Post by gerrykan » Wed Aug 05, 2020 2:19 pm

Check the motor oil too, in case some coolant got in the cylinder and got past the rings into the oil pan.
Roy

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Re: Low Compression on Rebuilt Engine | Dodge WC-63

Post by Bill H. » Wed Aug 05, 2020 6:36 pm

gerrykan wrote:
Wed Aug 05, 2020 2:19 pm
Check the motor oil too, in case some coolant got in the cylinder and got past the rings into the oil pan.
Good thought.

Hunter, let it sit overnight and just crack the drain plug. Coolant will settle in the bottom and come out if it has any in the crank case.
Bill H.

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1962 AMC M422A1
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