willysmjeeps.com

how can you tell if your M38 engine has the new style reinforced rear engine flange? ...anyone got some pic.?.. my M38 has replacement engine # RMC11827.....thanks ...Kent....

The cast flange of the old block rear end only had the four 3/8" bolt holes. The late style block has more meat in both sides of the flange and has the same four 3/8" bolt holes plus an additional three 5/16" bolt holes on each side vertically between the upper and lower 3/8" bolt holes. This late block only has 2 freeze plugs on the passenger side where the early block has 4.

Here they are in their order of appearance:











You can go to my Engine album and view other angles.
http://www.willysmjeeps.com/v2/modules. ... _album.php

The series one 641987 engine may have been around yet in Dec 49 when the Pilot M38's were contracted.

Series 2, 3 & 4 go up to eng serial MC74419 in Feb 52. Series 4 continued thru Jun 52 when the 804380 showed up.

A little history if you don't have Ryan's book. The new style engine was introduced on drawings in Dec 51. By mistake it went to the foundry leaving the old 641087 casting number on it even though the drawing called it out as 804380. A hundred of these were test installed on the line in Dec 51. It wasn't until April/May 52 that the drawing was corrected by amendment and the casting number 804380 finally shows up in Jun 52. We have no record to this date of a MCXXXXX serial on an 804380 block. I only have records of RMCXXXXX engines as 804380 blocks.

Wes; my motor looks to be a series 3 although I don't see but 2 freeze plugs & I have it out on my engine stand....it has just 2 bolt holes at rear...motor # MC44089....head casting # 800376... motor casting # 641087....serial # on dash plates & tub MC 61701...dated 4-52....thanks for your help ....Kent

sorry I entered wrong engine # in the first post....that # is off a spare that I have in the shed

Post a photo of the right side of your blocks

who is & where do you get this Ryan's book you are referring to ??

Ryan Miller and I established this web site in 2005. I had been running the Yahoo M38/M38A1 group since 2002 and Ryan and I decided to move everything to this format. Ryan along with a few guys helping wrote the M38 Parts guide and got it published a little over 2 years ago. Most of the M series jeeps vendors carry the book.

Here's my 2 cents: Great Book! Lots of good detail, pictures, and information. Wes and Ryan are a huge resource to go to for info on these jeeps. Thanks guys!
-JJB

thanks for the info & help & the website...will order the book...take care >>>Kent

Wes; the block in my 52 M38 is cracked & is the series 4 block ...I have a good series 3 block will this fit or will I need to change the bell housing ?...now that I have it out I can see that the plate on the back ,flywheel & starter are different...have a parts M38 that has a good series 3 block that I can rebuild ....thanks for any help ...Kent

You can use either engine with either bell housing but the adapter plate that matches the bell housing must be used. In your case you will want to use the front timing cover and crank pulley from your series 4 engine.

Hello,

Hope these images from my M38 could be useful.


By m38_carioca at 2012-02-05


By m38_carioca at 2012-02-05



By m38_carioca at 2012-02-05


Regards,

Carioca