J series engine number lookup

Harleygaz · Post by **Harleygaz** » Mon Aug 12, 2019 8:24 am

My M38 has a J series engine. Is there a database for these engines where I could find the year etc?

mbullism · Post by **mbullism** » Mon Aug 12, 2019 9:16 am

J series is a CJ2a engine. I'm not aware of a database specific to ESNs, but you may be able to narrow it down seeing where it fits in the 2A database...

http://cj-2a.com/parts_list/CJ2A_data.php

Post by **wesk** » Mon Aug 12, 2019 11:11 am

Post the full serial and casting numbers so we can offer a more precise answer. The J series engines came in several flavors, JXXXXX, CJXXXXX, CJ2AXXXXX, 3JXXXXX to name a few. Since Willys did not match engine serials to chassis serials as the GPW did during WWII Willys jeeps both military & civilian can only estimate approximate engine serials by date.

Harleygaz · Post by **Harleygaz** » Mon Aug 12, 2019 2:16 pm

Engine number is J156681. I don’t have the casting number right now. I’ll get it tomorrow morning.

Harleygaz · Post by **Harleygaz** » Tue Aug 13, 2019 8:54 am

The casting number is under the oil filter bracket which I don’t want to remove. I have pictures of the head and block. I read the faq on posting pictures but I have no idea how to put them in a public access space on the internet. Any suggestions?

mdainsd · Post by **mdainsd** » Tue Aug 13, 2019 1:46 pm

wesk wrote: Since Willys did not match engine serials to chassis serials as they did during WWII with the MA/MB post WWII jeeps both military & civilian can only estimate approximate engine serials by date.

I cannot speak to the MA as I have never researched them. But the MB chassis and engine numbers do not match. The engine number is higher than the chassis number and that numerical difference continued to climb through production.

The Ford GPW however, had matching serial number plate, stamped frame number and stamped engine number throughout production.

mbullism · Post by **mbullism** » Tue Aug 13, 2019 3:05 pm

ESN J156681 seems to fit the 2A database late '47, right around 2A SN 146428 with ESN J156598A...the optional comments provided show that jeep purchased new 12/22/47

I think to get any "closer" you'd have to sift for published ESNs above and below in the service bulletins and interpolate. If you pull the oil pan you may find a machining date on the block back by the rear main, the month will be a letter code if there

Post by **wesk** » Tue Aug 13, 2019 8:45 pm

But the MB chassis and engine numbers do not match.

My BAD I meant to say GPW but I confused the issue while remembering that WWII willys were the only ones that used a frame serial along with a matching dash serial plate.

The casting number on the head under the oil filter bracket is for the HEAD!

The block casting number is easily read:

As was mentioned above, the vehicle serials did not match the engine serials. Not mentioned above, was the serials are consecutive for all L134's and the only thing that changes are the prefixes. Therefore interpolating is not an easy task. For example using the M38 and the 641087 casting serial numbers are all consecutive even though some have the prefix MC, or RMC, or 3J. In this case we could assume 5,000 consecutive serials got the prefix MC then the next 2,000 may have gotten the prefix 3J and then the next 1,000 the prefix MC. To decipher the CJ2A data base or the M38 data base you can only look for several liste jeeps of the same model with engine serials very close then you could assume it is reasonable that those similar serialed engines were produced and installed in that small group of jeeps and the other engine serials that were not close were obviously not used during that period. The other problem is engines were not withdrawn from assembly line stocks in any certain order.

Post by **wesk** » Tue Aug 13, 2019 8:58 pm

ESN J156681 seems to fit the 2A database late '47, right around 2A SN 146428 with ESN J156598A...the optional comments provided show that jeep purchased new 12/22/47

Can you post the link for that data base?

mbullism · Post by **mbullism** » Wed Aug 14, 2019 10:49 am

wesk wrote:Can you post the link for that data base?

In my post above and repeated here:

http://cj-2a.com/parts_list/CJ2A_data.php

If you scroll the page globally there is a horizontal scroll bar at the bottom so you can reveal the ESN column, and I find it easier to scroll the ESN to the left to be adjacent with the years and SNs... If you click on the blue SN for any jeep it brings up a summary page for that individual jeep with all of the table info (sometimes easier than scroll left and right)

It's a bit easier to interpolate 2A's because there weren't so many pulls on the output stream, but I generally feel like interpolating a day is really more than likely identifying a week.

Post by **wesk** » Wed Aug 14, 2019 12:46 pm

My BAD. Sorry about that. Didn't connect your 2nd post with your 1st post. I'll do my best to not miss that again.

Harleygaz · Post by **Harleygaz** » Wed Aug 14, 2019 3:48 pm

Casting number is 641087. To the left of it (towards the rear of the engine) is 6. Engine number definitely only has a J prefix, no other letters. I checked the transmission and transfer box and they have the fording vent lines so I think the swap was just the engine, manifolds, carb and exhaust. Bell housing doesn’t seem to be the watertight version from the M38.

mbullism · Post by **mbullism** » Wed Aug 14, 2019 5:02 pm

wesk wrote:My BAD. Sorry about that. Didn't connect your 2nd post with your 1st post. I'll do my best to not miss that again.

Please, lol... (didn't mean it that way, but I see it now

)

mdainsd · Post by **mdainsd** » Wed Aug 14, 2019 5:27 pm

Early M38s didn't have a waterproof bell housing.

Harleygaz · Post by **Harleygaz** » Wed Aug 14, 2019 5:44 pm

Mine is serial 69581, May 1952. Judging from what I’ve read it must have been within the last 3000 made.