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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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by 17thAirborne » Mon Mar 05, 2018 8:00 am

Johnr wrote:
Sun Mar 04, 2018 10:22 pm
I believe this is the updated universal jeep page referenced.

Cheers
John

Jeep crank 2.jpg
Great post...thanks
Oz

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

Post by Chuck Lutz » Mon Mar 05, 2018 10:17 am

Personally, I know of no jeep owner who has determined that his poor compression would be solved with oversized rings and that this would be as far as they would go to "rebuild" their engine. Likewise, if one somehow determined that the rod bearings were worn out (low oil pressure) and needed replacing that this is as far as they would go and not pull the crank to replace the mains?

This is backyard/Bubba stuff. If your engine has poor/uneven compression and you have poor/low oil pressure....then you should do what is called a REBUILD...and that means pulling the engine and doing everything to insure you get another 50-70 years of use from it!

Arguing over removing the ring ridge should not be an issue....your compression issue may be an out-of-round cylinder wear problem and as such, oversized rings ain't the solution. Trying to improve oil pressure by replacing rod bearings with the crankshaft in situ is doing only HALF the job. If they are worn then the main bearings probably suffer the same wear.

When one buys a jeep with a poorly running (if at all) engine, it is probably time for a REBUILD....and that means doing everything....starting with dismantling it, checking for wear/cracks/etc. and then pressure testing, magnafluxing and actually machining things back to spec.

How many times you want to have to "rebuild" your engine because you cheaped-out and didn't do it all the first time is something only YOU will have to find out.

Unless you have a machine shop at your disposal and the knowledge to do it yourself....it will cost you big bucks to keep "rebuilding" that engine because you really didn't "rebuild" it the first time around. You can either "rebuild" that engine or keep on "fixing" it....that's up to you, "in for a
Penny, in for a Pound".

Just my two centavos...
Chuck Lutz

GPW 17963 4/24/42 Chester, PA. USA 20113473 (USA est./Tom W.)
Bantam T3-C 1947

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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by Marty, SoCal » Mon Mar 05, 2018 12:49 pm

Some people don't have the money to repair their jeep to perfect condition.

One common scenario where you would be able to just replace the rings is if the engine overheated and the rings lost their tension but the bore is still within spec.

Another is when replacing a damaged piston.

A ridge reamer is or at least was 15 years ago a required tool at any shop wishing to be recommended by the AAA auto club for repairs. I remember we had to buy one at the dealership because of that. (None of the techs had one!) You had to employ ASE techs and have a minimum set of tools to get their recommendation.

A buddy of mine had a Willys L134 in his GPW it was pumping oil bad one cylinder. Pulled the head and dropped the pan removed the piston, and found the expander was broken on the oil ring (Modern 3 piece type). Luckily I had a good used expander in my stash from another job and installed it and it stopped the oil pumping. Didn't need to ream the ridge, as the bore had little wear.
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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by artificer » Mon Mar 05, 2018 1:07 pm

There are some really good practiced mechanics, experienced in the real world of automotive repair offering solutions on the G.
Then there are a few wannabes without training, knowledge or practical hands on experience preaching their unfounded opinion to the masses.
Re-ringing was & still is a practical option when wear is within limits, no matter what anyone thinks.
There are many different brands of rings that will suit a 3.125" & oversize bore but those who are not tradesmen would never think of using them [to their cost & detriment].
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by Joe Gopan » Mon Mar 05, 2018 1:26 pm

My experience over the years with 4 Cyl Jeep engines is that if the cylinder taper exceeds 0.005" or 0.006", installing replacement rings that compensate for the taper is a waste of money, especially if the jeep is a daily driver as the job is only good for a few thousand miles before excess oil consumption returns. Reboring with matching oversize pistons and rings will return the bore to original specification and the jeep if serviced and driven with care will give another 30-40,000 happy miles.
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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by Marty, SoCal » Mon Mar 05, 2018 1:37 pm

.005"-.006" taper, I agree, time for a re-bore.
43 Ford GPW 92098
53 Dunbar Kapple M100
Sold: 61 CJ-5, 41 T207 WC-1 Dodge closed cab pickup
MVPA #8266
USMC Tanker (1811, 1812), 85-93
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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by Joe Gopan » Mon Mar 05, 2018 2:17 pm

I had a 1st time tear down GPW engine that had a 0.019 taper, never saw an all original Jeep engine with that much taper before.
I bored it out to 0.030".
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by artificer » Mon Mar 05, 2018 2:25 pm

Joel wrote: I had a 1st time tear down GPW engine that had a 0.019 taper, never saw an all original Jeep engine with that much taper before.
I bored it out to 0.030".
Probably dusted?
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by Joe Gopan » Mon Mar 05, 2018 2:31 pm

Gasoline washed is my guess,it does not take long.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by Marty, SoCal » Mon Mar 05, 2018 3:59 pm

Another handy tool to have while re-ringing is a ring groove cleaner:

Image

About $19 from Summit Racing:
https://www.summitracing.com/parts/lil- ... e2-_-lisle

Video:

https://www.youtube.com/watch?v=JbnzMrqE_88

I'm speculating that this tool would be used on a piston to cut the depth needed for the expanding rings mentioned above using the patented depth gauge to get it to the right depth.

I'm a cheap bastard I simply break off one of the old rings and use it to scrape the grooves clean.
43 Ford GPW 92098
53 Dunbar Kapple M100
Sold: 61 CJ-5, 41 T207 WC-1 Dodge closed cab pickup
MVPA #8266
USMC Tanker (1811, 1812), 85-93
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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by artificer » Mon Mar 05, 2018 4:41 pm

Marty wrote:I'm a cheap bastard I simply break off one of the old rings and use it to scrape the grooves clean.
That really does a number on your fingers/hands though?
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by Marty, SoCal » Mon Mar 05, 2018 4:56 pm

Yep! but I've cut my hands so many times I don't feel cuts anymore. Usually I'm bleeding somewhere at least once a day! :roll:
43 Ford GPW 92098
53 Dunbar Kapple M100
Sold: 61 CJ-5, 41 T207 WC-1 Dodge closed cab pickup
MVPA #8266
USMC Tanker (1811, 1812), 85-93
ASE Automotive Master tech, former Chrysler-Jeep Level 4 Mastertech, CA state EA smog license

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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by artificer » Mon Mar 05, 2018 10:47 pm

0.002" doesn't need a rebore & will not be burning oil either.
We are talking WW2 Jeeps here, are we not?
Modern segmented oil rings need to be understood....
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by 17thAirborne » Tue Mar 06, 2018 5:07 am

I tell you what. We've had enough spirited discussion about re-ringing with and without machining. I think everyone who has read this thread can decide if they want to re-ring or not. The next guy who posts a point-counter-point about re-ringing with or without machining is a Fekkin Eedjit. (Go read your Irish dialect if you can't translate) :lol:

Please let's allow good discussion. Thanks to all who keep posting more advice and experience to keep us novice engine builders on track. That is why I started this thread.
Last edited by 17thAirborne on Tue Mar 06, 2018 9:49 am, edited 1 time in total.
Oz

Feb 43 GPW 98532 USA 20206257
Oct 70 Land Rover Series 2a 25334079G NZ16GF36
http://gpw.castraponere.com/ (My Restoration Page)

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Re: WARNING!!! Rebuilding GPW/MB Engines

Post by KiwiMB » Tue Mar 06, 2018 8:49 am

Begorah, the man is right, lets put this one to bed!

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