Engine ID

Herrmann_Sherman · Post by **Herrmann_Sherman** » Sat Dec 10, 2011 12:30 pm

The ID on the engine of my M38 is polished off.
But on the passenger side on the block are some numbers.
Is anybody there who can tell me, is this the ID of the engine?

641087-LW-11a

Is it a M38 or a CJ3A Block?

Many thanks
HS

evanso1975 · Post by **evanso1975** » Sat Dec 10, 2011 1:23 pm

That is a casting number. 641087 was used on the CJ2A, CJ3A and M38. Are there any numbers cast on the driver's side?

And can you post some photos of your engine block? This would help the folks on this website to try and ID your engine....

Wbr,
Owen.

Post by **wesk** » Sat Dec 10, 2011 2:32 pm

Without the serial number on the flat above the water pump you will never be able to determine what model jeep it left Willys in.

The fact that is is one of the two casting numbers used on the M38 only qualifies it to fit in an M38. The very early versions of the 641087 casting with 4 freeze plugs, date clock and the oval serial pad on the top right side behind the oil filter would not have come in an M38. The numbers on the driver side will offer a clue as to date of manufacture but the block casting was used in several jeep models as well as the M38 simultaneously from Sept 1950 thru July 1952. So again without the serial number from the top of the block you can never ascertain what model it came in.

evanso1975 · Post by **evanso1975** » Sun Dec 11, 2011 9:39 am

The ID on the engine of my M38 is polished off.

It's possible the serial number might still be there. Try rubbing the serial number area with french chalk, and wiping it off with a dry cloth. Worth a try anyway.

Herrmann_Sherman · Post by **Herrmann_Sherman** » Sun Dec 11, 2011 10:24 am

I will do so. And let you know!

regards HS

vrod02 · Post by **vrod02** » Sun Dec 11, 2011 4:58 pm

Without the serial number on the flat above the water pump you will never be able to determine what model jeep it left Willys in.

If its bolted COMPLETELY around the bellhousing its not civvy correct?
I've been searching right or wrong for yrs just peeking underneath.

Post by **wesk** » Sun Dec 11, 2011 7:51 pm

No, Vrod, No serial number means no way to tell which model it left Willys in. The basic block can have any accessories installed on it you want but since over 50 years have elapsed there's absolutely no other way to tell for sure except by the serial number. The bell housings will fit either block.

vrod02 · Post by **vrod02** » Sun Dec 11, 2011 8:16 pm

I looked at my post and will ask again,sorry.
Regardless of cast numbers

Did all M38 blocks come with complete surround bolt up to the bell housing?

Did any m38s come with the cj2-3a block to bellhousing bolt up setup?

Did any other willys models, not generators, with L134's come from the factory with "standard" M38 block to bellhousing set up?

I'm asking for the simple reason of someone milling the horn/block down on a civvy engine and punching their own MC numbers to match frame.

Post by **wesk** » Sun Dec 11, 2011 10:20 pm

There is no M38 block to bell housing special arrangement. The M38 engine bolted to the bell housing in 1950 the same way the CJ3A and CJ2A engine bolted to the bell housing. And the casting number on both was 641087.

The later (Dec51/MAR52) style rear block flange on the M38 641087 casting was exactly the same as the later (Dec51/MAR52) CJ3A 641087 casting.

The new block casting 804380 in 1952 was the same for both the M38 and the CJ3A.

As I have said there is only ONE way to determine without any doubt which model jeep a Willys engine casting came in> Yhe serial number

I can take any late CJ2A, CJ3A 641087 block casting and grind the pad above the water pump and duplicate the size, shape, depth and spacing of the MCXXXXX serial number and you cannot prove it is not an M38 block.

I think you are confusing the why and when and how of the 641087 block casting update in Dec/March 1952 from the four 3/8" rear flange bolts to the four 3/8" rear flange bolts plus 3 more per side 5/16" bolts. This was an across the Willys production line change that affected all models using that block at that time.

This 1950 thru Dec 51 641987 block was used in both the CJ3A and the M38 as well as other Willys products.

This Jan 1952 thru Jun 1952 641087 block was used in both CJ3A's and M38's and other Willys products.

This 804380 casting introduced in JUNE 1952 was used on both CJ3A and M38 and other Willys products.