Dating my block

davem201m38 · Post by **davem201m38** » Sun Nov 01, 2020 8:41 am

Hello all,
I’m trying to date my M38 block. It is the later rear flange type modified for better fording i believe.
Behind where the drag link would be I have the following cast into the block.
2 6 D. Is the June 2nd 1952 ?

The long casting number is, 641087 L W 13A. N1 CR N2
Thanks, Dave.

RonD2 · Post by **RonD2** » Mon Nov 02, 2020 9:19 pm

Hi Dave,
Is there a serial number on the block (on the boss above the water pump) --- a MCXXXXX or RMCXXXXX number? That might be your best indication to zero in on a date of manufacture bounced against the known data base.

If the oil pan is off, I believe Willys also stamped a machining date into blocks on that mating surface on one of the corners near the rear main --- if I recall correctly. I believe that blocks were cast a long time before they were machined... (seasoning time).

I think casting numbers will only give you an early or late rough idea of the date of manufacture.

I'm sure Wes can add a lot more answers to your question. He must be busy.....

Good luck!

RonD2 · Post by **RonD2** » Tue Nov 03, 2020 11:59 am

And these posts might be helpful:

http://willysmjeeps.com/v2/modules.php? ... hlight=rmc

http://willysmjeeps.com/v2/modules.php? ... block+date

Post by **Ryan_Miller** » Fri Nov 06, 2020 11:36 am

Ron is spot on.
I have the blue print for the block castings but it is extremely long and large so cannot post it.

Also do you have the water jacket hole at the back of the block, probably not since you have the later style mounting flanges.

davem201m38 · Post by **davem201m38** » Sat Apr 03, 2021 4:40 pm

Hum, the water pump boss has no number,Which I thought odd. Where am I looking for the water hole in the back of the block?
Ta, Dave.

45auto · Post by **45auto** » Sat Apr 03, 2021 5:37 pm

Your casting stamping of 2 6 D is February 6th 1952. Which tells you when the Block was cast, not when it was assembled.
What is the Date of Delivery on your M38?

Post by **wesk** » Sat Apr 03, 2021 8:16 pm

Dave,

The usual cause of the missing number on the water pump boss is a previous decking of the block during an overhaul. In many cases the missing numbers are actually still visible with a little bit of sleuthing about like a detective. Some dye penetrants and magnetic powder methods can make the number somewhat visible. Unfortunately without that number it is impossible to determine for sure that the engine you are looking at is original to your jeep.