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    Posted: 12 Jan. 2010 at 9:51am
Why would some M38 motors be stamped MCXX.... and some be stamped RMCXX....?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpet Quote  Post ReplyReply Direct Link To This Post Posted: 12 Jan. 2010 at 10:11am
I found this thread where Gale says that the "R" probably stands for rebuild.
 
Can anyone confirm this?
 
The MB that I have has an MC motor.  "RMC15268"  I am trying to determine if it would be possible that the motor was put in by military personnel while the vehicle was still in service or was it definitely replaced by a civilian after service.


Edited by jpet - 12 Jan. 2010 at 10:12am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bkreutz Quote  Post ReplyReply Direct Link To This Post Posted: 12 Jan. 2010 at 10:14am
MC would be the prefix for an original engine, the "R" would indicate a replacement. MC being the designation for a M38 (following the military model designation sequence, MB being the WWII version, and MA the model before that)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpet Quote  Post ReplyReply Direct Link To This Post Posted: 12 Jan. 2010 at 10:24am
Originally posted by bkreutz bkreutz wrote:

.....the "R" would indicate a replacement. .......
Originally posted by bkreutz (from Engine Serial numbers) bkreutz (from Engine Serial numbers) wrote:

the MC would be a correct engine for the M38, the R stamping probably denotes that the engine was rebuilt.
http://www.thecj2apage.com/forums/m38-motors_topic13777_post115160.html#115160
What I mean is, what was the method?  Did they yank a motor from a jeep, rebuild it, stamp an "R" in front of the serial number and then put it on a shelf till someone needed it? Or .... Did they rebuild the motor, stamp an "R" in front and put it back in the same vehicle it came out of? Or ...both? Or ... is an "RMC" motor a new motor and not a rebuild? Or ... something else?  or don't know?
Know what I mean?

Edited by jpet - 12 Jan. 2010 at 11:34am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bkreutz Quote  Post ReplyReply Direct Link To This Post Posted: 12 Jan. 2010 at 12:35pm
I've always thought the "R" prefix was a replacement not a rebuild, so to answer your question (at least as far as I knowLOL) The "R" would be a new motor. I'm remembering motor pool rebuilds had a separate rebuild tag attached somewhere else.


Edited by bkreutz - 12 Jan. 2010 at 12:36pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jeepfreek Quote  Post ReplyReply Direct Link To This Post Posted: 12 Jan. 2010 at 12:56pm
hi.i believe gale is right.r is for replacement.when new jeeps were ordered a supply of parts was also ordered along with replacement engines.regards jim.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpet Quote  Post ReplyReply Direct Link To This Post Posted: 12 Jan. 2010 at 1:16pm
What can you tell me about the 15268 number after RMC?
 
I guess what I am trying to do is decide whether or not to keep the motor.  If I could determine that there is a reasonable chance that the motor was put in by a military mechanic while the vehicle was in service, I would want to keep it.  If the motor was most likely put in after service by a civilian, I would certainly replace it with one that was more "numbers matching".
 
Maybe it is impossible to do.  I can't seem to find M38 motor data like what we have here on 2A motors.


Edited by jpet - 12 Jan. 2010 at 1:17pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Viking Quote  Post ReplyReply Direct Link To This Post Posted: 14 Jan. 2010 at 4:00am
Hi Jpet.
As earlier said in this tread:
Willys MA = Military modell A. Engine block casting number: 638632
Willys MB = Military modell B. Engine block casting number: 638632
Willys MC = Military modell C. Engine block casting number: 641087 up to s/n 74419 then 804380.
 
What is the casting number on your block? 
I have no info/proof about RMC, but it would be interesting to see if the stamping was done at the "same" time.
  • "R" stamped in front of MC, but not by the same stamp...
  • "RMC" stamped at the same time....
If the R was stamped in later than the MC I would say Rebuild, but if the RMC was stamped at the same time I would guess "R" was placed there to indicate a replacement engine.
again....NO PROOF, just my thoughts.
 
You will find a couple of photos here: http://ww2jeeps.com/htm/willysmc.htm
The serial number on your block (15268) puts it in the "early" period. There is supposed to be a change in the aft part of the block to improve sealing when fording on the late blocks.
 
 


Edited by Viking - 14 Jan. 2010 at 4:10am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jeepfreek Quote  Post ReplyReply Direct Link To This Post Posted: 14 Jan. 2010 at 10:05pm
hi jpet.i talked to the guru on m38 jeeps around here in ontario today.he says the r stands for replacement.the serial no is just a seq. no that he says did not have a lot of meaning.regards jim.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote leomartin6 Quote  Post ReplyReply Direct Link To This Post Posted: 28 Apr. 2010 at 5:36am
I have found a lot of useful stuff from here. I mean it is helpful from the technical point of view to use practically.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BillF Quote  Post ReplyReply Direct Link To This Post Posted: 28 Apr. 2010 at 12:43pm
Yes the R stands for replacement.  I have an RMC engine in my m38.  The numbers after the RMC are the engines serial numbers.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mazeem1234 Quote  Post ReplyReply Direct Link To This Post Posted: 04 July 2011 at 7:20am
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Edited by sean - 10 Nov. 2011 at 8:35am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote m38mike Quote  Post ReplyReply Direct Link To This Post Posted: 04 July 2011 at 10:37am
 Jpet, the info you're getting here is spot on, R is replacement, and was put in after the vehicle entered service.  The problem with your quest to know if it was put in during service or after service is that many replacement blocks were sold as surplus when the military phased out the M38 in the 60's.  There is no definitive way of telling when the block was installed, but it very well could be military replacement.  One thought for investigating it is to look at all the connections to see if they are all done "text-book" or if they've been "modified".  If all the plumbing is text book, then it's either a meticulous mechanic, or a military one following the maintenance guide.  If not, it could be a "fix" by a shade-tree mechanic, or an install by a less exacting weekend mechanic.
 
BTW if you decide to sell, there is a demand for MC blocks in the M38 crowd.  There simply were not many made. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpet Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr. 2012 at 7:22pm
Well here is the engine stamp:



I can't tell if the "R" was stamped in later or not. Interesting enough, today I found that the motor also has a rebuild tag:



Now what have we learned if anything?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 52 M38 Quote  Post ReplyReply Direct Link To This Post Posted: 10 May 2015 at 6:59pm
Originally posted by jpet jpet wrote:

Interesting enough, today I found that the motor also has a rebuild tag:

 

JPET,  this is only other tag like mine i have ever seen.  Mine said Aberdeen on it instead, and it was hemi orange, just like the rest of the engine.  I have no idea why it would be orange. 
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