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M38 Factory replacement engines

 
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evanso1975
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Joined: May 10, 2010
Posts: 615
Location: North Yorkshire, UK

PostPosted: Mon Mar 12, 2012 2:12 pm    Post subject: M38 Factory replacement engines Reply with quote

The engine that came with my M38 is a factory replacement (RMC-######). Now, I found 4 holes in the flat area just between the distributor and the drain cock, spaced as if a rectangular plate would be riveted there (3-1/2" horizontally, 1-5/8" vertically).

Seems a little small, but I'm thinking that it may have been a motor pool rebuild plate. Do any members have any photos of such plates fitted to M38 engines that they would be willing to share?

Thanks in advance,
Owen.
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Owen

1951 US Air Force M38
1944 F-1 1/2-ton Airdrome Trailer
1940 C15 Chevrolet CMP 11-cab
1939 DKW KS200 Motorcycle
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RICKG
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Joined: Aug 31, 2010
Posts: 1739
Location: SO IDAHO

PostPosted: Mon Mar 12, 2012 2:51 pm    Post subject: Reply with quote

Mine isnt an RMC number, but in the photo below you can
see an ordinance depot plate with dates and bore info..
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RICKG MC 51986 DOD 01-52, '50 CJ3a
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wilfreeman
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Joined: Mar 13, 2006
Posts: 1079
Location: Richburg, SC

PostPosted: Mon Mar 12, 2012 5:43 pm    Post subject: Reply with quote

I know these 2 are mc engines, but you say replacement engine. Does it mean replacement or remanufactured (RMC*****)? Mine is RMD*****. I always thought it meant remanufactured. It's probably both - remanufactured replacement.
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Matt
1953 M38a1
1964 USMC M38a1
'51 USMC M100 trailer, '54 M100 trailer, '90 M101a1 trailer
Http://wilfreeman.wordpress.com (M38a1 build blog)
http://m38a1usmc.wordpress.com (USMC M38a1 rebuild blog)
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oilleaker1
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Joined: May 14, 2009
Posts: 971
Location: South Dakota

PostPosted: Mon Mar 12, 2012 6:57 pm    Post subject: Reply with quote

MC is flathead M38, MD is overhead valve M38A1 engine. R is replacement. John
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Oldsalt
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Joined: Jan 28, 2010
Posts: 179
Location: Texas

PostPosted: Mon Mar 12, 2012 7:40 pm    Post subject: Reply with quote

My M-38 doesn't have the plate, but the engine is an RMC. My M-38A1 does have a rebuild plate, but appears to be the original engine.

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AeroE
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Joined: Aug 31, 2008
Posts: 49
Location: SE MN

PostPosted: Mon Mar 12, 2012 8:41 pm    Post subject: Reply with quote

This tag is from one of my barn finds. It is a reconditioned engine with an MC prefix number. the tag is on the lower left rear side of the block.

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AeroE
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Joined: Aug 31, 2008
Posts: 49
Location: SE MN

PostPosted: Tue Mar 13, 2012 10:35 am    Post subject: Reply with quote

I want to take off my engine's tag before having the block cleaned. Anyone have ideas on how to remove the rivets without damaging the tag? There not really riveted, probably a friction fit. I’m thinking of locally heating the cast iron around the tag’s perimeter & maybe they can be gently pried out.

I’d appreciate any shared experience on this.
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evanso1975
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Joined: May 10, 2010
Posts: 615
Location: North Yorkshire, UK

PostPosted: Tue Mar 13, 2012 12:22 pm    Post subject: Reply with quote

Wow, a really fast response there folks. Thanks!

As far as I can tell, those plates all seem the be fitted at the base of the block. Now if you look at RickG's engine, there's a flat area directly below where the distributor mounts. On that flat area are 4 indentations that look like rivet holes for a data plate. This is the area I'm talking about in my original post.

So, do all M38 (MC) blocks have those 4 indentations there? Mine does, and so apparently does RickG's (which isn't a replacement motor). And what are they for? I originally thought the rebuild plate might go here, but it doesn't look that way from the photos. Confused

Owen.
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1951 US Air Force M38
1944 F-1 1/2-ton Airdrome Trailer
1940 C15 Chevrolet CMP 11-cab
1939 DKW KS200 Motorcycle
MVT # 19406
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wesk
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Joined: Apr 04, 2005
Posts: 16225
Location: Wisconsin

PostPosted: Wed Mar 14, 2012 1:22 am    Post subject: Reply with quote

The depot rebuild plates went where the plate mounting troop felt like putting them. I have seen many on both sides of the block.

Peruse my L134 block variations section of my photo album.
http://www.willysmjeeps.com/v2/modules.php?set_albumName=album70&op=modload&name=gallery&file=index&include=view_album.php
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php
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RICKG
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Joined: Aug 31, 2010
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Location: SO IDAHO

PostPosted: Wed Mar 14, 2012 9:48 am    Post subject: Reply with quote

Owen, My engine is MC74754. Curiosity got me looking closer..

heres the bare boss under the dist w/4 mounting holes.

the recond tag is located under the starter with 2 pins (note the tag
has a hole in each corner) it has a date of 2 58 and reconditioned
at P O D.. Pamona Ordinance Depot?? Perdition?? Paradise?? Hmmmm.
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RICKG MC 51986 DOD 01-52, '50 CJ3a
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jimm
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Joined: Nov 01, 2011
Posts: 199
Location: Escondido, CA

PostPosted: Wed Mar 14, 2012 3:33 pm    Post subject: Reply with quote

AeroE wrote:
I want to take off my engine's tag before having the block cleaned. Anyone have ideas on how to remove the rivets without damaging the tag? There not really riveted, probably a friction fit. I’m thinking of locally heating the cast iron around the tag’s perimeter & maybe they can be gently pried out.

I’d appreciate any shared experience on this.


The "rivets" are probably drive pins like those used to attach label plates on electric motors. Most of those have a helical (twisted) knurled surface so that the hole diameter doesn't have to be precise and the pin won't come out easily.

I wouldn't try your heating idea. Localized heating of cast iron isn't a good idea from a thermal stress standpoint, and it won't make the pin loose because it will heat up and expand right along with the cast iron. Center punching and carefully drilling them out would be a safer option. But then you would have to find replacements. I did a quick search for replacements and came up dry. Might all be in using just the right words in the search. If you have an electric motor rewind shop nearby, you might check with them to see if they have some pins.
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1952 M38 son-father project
Slowly turning rusty parts into OD parts
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evanso1975
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Joined: May 10, 2010
Posts: 615
Location: North Yorkshire, UK

PostPosted: Wed Mar 14, 2012 4:15 pm    Post subject: Reply with quote

Some of the photos in Wes's album there have the 4 holes drilled in that flat area, and some don't. I guess if the motor pool guys got the engine rebuilt and forgot about fitting the plate, they wouldn't take the distributor off; they'd go for the easiest option. Wink

Totally agree with drilling those rivets out, rather than heating the block. In the UK, those rivets are called "hammer drive screws", cos you hit them with a hammer and it, er, drives them in. Shocked Just personal preference, but I'd go for stainless ones.....

Owen.
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1951 US Air Force M38
1944 F-1 1/2-ton Airdrome Trailer
1940 C15 Chevrolet CMP 11-cab
1939 DKW KS200 Motorcycle
MVT # 19406
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wesk
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Joined: Apr 04, 2005
Posts: 16225
Location: Wisconsin

PostPosted: Thu Mar 15, 2012 5:03 pm    Post subject: Reply with quote

1- I believe the pads cast under the distributor were originally without holes and those that had plates added in the field would have drilled the holes you now see.

2- Here in the US where I have worked in these trades the name for those plate fasteners is "Drive Screws".
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php
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jimm
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Joined: Nov 01, 2011
Posts: 199
Location: Escondido, CA

PostPosted: Fri Mar 16, 2012 5:24 pm    Post subject: Reply with quote

And, as usual, once you know the right name for something, it is easy to find it on McMaster-Carr's website: http://www.mcmaster.com/#drive-screws/=goyzla
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Jim McKim
1952 M38 son-father project
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