WARNING!!! Rebuilding GPW/MB Engines

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
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17thAirborne
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WARNING!!! Rebuilding GPW/MB Engines

Post by 17thAirborne » Sat Feb 10, 2018 12:44 pm

Although I have nearly 3000 posts as of this posting date, I am a novice when it comes to rebuilding and restoration. Do not place any credence to my comments based on my join date or my number of posts, but on what follows in the comments by those who ARE seasoned engine builders. I will relate a story, probably not unlike the many other Jeep engine rebuilding stories that have been repeated before over the last 75 years. Some are documented on the "G", but many hidden in past pages, and invisible to the novices like myself. You only know what you learn, experience or observe, and I have recently learned about the mis-print in TM 9-1803A.

Thankfully it was not my engine, it was a friend in the middle of two GPW engine rebuilds. He is a trained and seasoned heavy diesel and gas engine mechanic, with recent experience in the 134. He is driving down the road in his newly machined and rebuilt GPW engine, all F marked and he hears a loud cyclical metallic knock that gets worse with speed and rmp. He drives home, drops the engine and finds the No 4 bearing melted to the crankshaft.

He calls me a few days later 'cause we're MV buddies and I'm learning about rebuilding a Flat-head T-214 for my WC12. He had ordered a new No. 4 F marked rod from Brent Mullins to replace the ruined one and called to tell me that Brent sent him the wrong rod. He ordered a 2/4 and received a 1/3. Together we dig into the TM (excerpt published with corrections below). Now we are both confused, because he said he installed all his rods with the offset away from the nearest main bearing. Over the course of the next hour, I find the hidden post about the misprint in the TM and now everything makes sense. The offset is supposed to be installed toward the nearest main bearing. It turns out Brent DID send the CORRECT rod. After my friend laid everything out facing the correct way, he had one No. 2/4 rod and three No 1/3 rods. I don't know if that is what caused his problem before, but I do know it ain't good to have the wrong rods in the wrong cylinders.

PLEASE, those of you who know what is correct, please comment here and affirm that what I have posted regarding the TM is correct. If it is not, I will change it and update the image so that no one else makes this mistake as my friend did. My next rebuild is going to be a GPW, and I want to get it correct. If this were a sticky, my friend might have read this.
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Last edited by 17thAirborne on Sat Feb 10, 2018 12:53 pm, edited 1 time in total.
Oz

Feb 43 GPW 98532 USA 20206257
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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by Joe Gopan » Sat Feb 10, 2018 12:52 pm

It is also a good Idea for those who work on their own 4 Cyl Jeep engines to purchase a copy of the Jeep factory Service manual for the CJ-2A thru CJ-5. It is a good companion to the TM and will enhance your overall Jeep engine knowledge.
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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by 17thAirborne » Sat Feb 10, 2018 12:54 pm

Ben Dover wrote:
Sat Feb 10, 2018 12:52 pm
It is also a good Idea for those who work on their own 4 Cyl Jeep engines to purchase a copy of the Jeep factory Service manual for the CJ-2A thru CJ-5. It is a good companion to the TM and will enhance your overall Jeep engine knowledge.
Great recommendation...so the change I posted above is correctly annotated?
Oz

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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by Mike Wright » Sat Feb 10, 2018 1:28 pm

Hi OZ,
Indeed you posted correct info. With that being said here on the "G" I have read accounts of 134 engines that have gone thousands of miles with the rods incorrectly assembled and only discovered upon a recent rebuild. Point being there may have been an other issue that caused your friends bearing meltdown. blocked oil passage, bearing pin came loose, etc. Check very carefully!
HTH and GREAT review!
Mike
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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by dpcd67 » Sat Feb 10, 2018 1:31 pm

Yep, fortunately, I had the CJ Universal book first, before I did any WW2 engines. But for those just starting to build L134s, well, we just have to get the word to them that the TM is wrong. It's easier now with this internet thing. I hope his block is fixable.
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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by 17thAirborne » Sat Feb 10, 2018 1:47 pm

Mike Wright wrote:
Sat Feb 10, 2018 1:28 pm
Hi OZ,
Indeed you posted correct info. With that being said here on the "G" I have read accounts of 134 engines that have gone thousands of miles with the rods incorrectly assembled and only discovered upon a recent rebuild. Point being there may have been an other issue that caused your friends bearing meltdown. blocked oil passage, bearing pin came loose, etc. Check very carefully!
HTH and GREAT review!
Mike
Thank you for posting. I am not sure he will ever know why it malfunctioned. He's having everything checked to make sure and starting over. I would urge him before he started to put a micrometer to everything and write the numbers down as my 42WLA mentor taught me.At least you know the starting point, and do it again after the machinist is done to verify before the first start. I now am an official lover of plasti-gauge! :lol: BTW, that's not a sexual thing. :shock:
Last edited by 17thAirborne on Sat Feb 10, 2018 2:59 pm, edited 1 time in total.
Oz

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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by 17thAirborne » Sat Feb 10, 2018 1:48 pm

dpcd67 wrote:
Sat Feb 10, 2018 1:31 pm
Yep, fortunately, I had the CJ Universal book first, before I did any WW2 engines. But for those just starting to build L134s, well, we just have to get the word to them that the TM is wrong. It's easier now with this internet thing. I hope his block is fixable.
Sounds like more of ya know about the CJ data which makes sense being full of all of the lessons learned over the years. I think he was smart in pulling over and was not too far from home when it happened. He should be GTG.
Oz

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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by artificer » Sat Feb 10, 2018 7:08 pm

A number of things can be added.

As a good mechanic should (on any engine rebuild)...look up from the crank to piston & the piston pin should have equal distance/space showing on each side between the connecting rod & piston pin bosses.

Fitted incorrectly as the TM misprint indicates & this space will not be similar but well off to one side.

It is also likely the incorrectly offset con rod little end will cause the piston pin to be wearing a groove in the cylinder wall.
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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by 17thAirborne » Sat Feb 10, 2018 10:07 pm

Thank you John.
Oz

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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by Wolfman » Sun Feb 11, 2018 5:57 am

The original TM was misprinted and what is said here is true.
Want to bring up what Mike Wright said in his post one more time. He sliped it into a sentence and this is important.
The main bearing locating pins. Well built engines have failed because these were left out and it is easy to do. Especially for those that are acustomed to building more modern engines.
Modern engines keep the main bearing shells located with tabs that fit into notches in the block and main caps.
L-134s have locating pins that fit in holes in the center of the block and caps. Steps, on these pins, fit into holes in the main bearing shells to keep the shells located properly. If the pins are left out, the shells can slowly creep out of position, blocking the oil passages in the block and the end result is similar to your friends situation. The engine runs OK initially but soon self destructs from oil starvation to the bearings.
Don't forget to install the locating pins.
Will agrre, installing the rods according to the misprint will not cause immediate self destruction. Just shorten over all engine life.
Mike Wolford
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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by 17thAirborne » Sun Feb 11, 2018 6:07 am

Great post. Thanks Mike
Oz

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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by artificer » Sun Feb 11, 2018 6:14 am

To add to Mike's post....the main bearing 1/2's only have an oil drilling in 1 half. Fitting incorrectly is possible & can block off the oil supply drilling from the engine block to main bearing. This drilling supplies oil through the crank to big end/s.
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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by Joe Gopan » Sun Feb 11, 2018 7:03 am

The factory manuals note these precautions.
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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by 17thAirborne » Sun Feb 11, 2018 7:04 am

It seems the heart of the life on these engines is the PROPERLY fitted and installed bearings (Mains and rods). There is much to add regarding turning and polishing the journals, and just as much about installing and sizing the bearings. I would also add that even after the turning, polishing and installing is done, there is a measure of comfort in properly checking the fit with plasti-gauge before final assembly.

Of course, supplying a proper quantity and type of oil under pressure is equally important.
Oz

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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by harve » Sun Feb 11, 2018 7:48 am

Same exact thing happened to me on my last 3A engine i had rebuilt , carbon copy of events


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