engine serial number help

[ShawnH]

Hi all.I have a 52 M38 that I have just started getting into/tearing apart.Was looking at the engine serial number and was hoping you could help decode it for me.MC78441...but looks like it was stamped over with other numbers...does this mean it was rebuilt at some point?I hope these forums don't go away.I cant tell you how much I have learned from them already! Thanks,Shawn

[wesk]

The serials started with MC10001. Subtract that and you have the sequence of production of your engine. So that engine was the 68,440th M38 engine out the door. Trouble with the arithmatic here is the MCXXXXX and the RMCXXXXX were produced with sequential serial numbers. For example let's imagine it's about Oct 1950. They already assembled 2000 MC engines. Well the contracts also called for spare engines and required the spares to be built intermittently during production of the regular factory install MC engines. So we build 2000 MC engines that start with MC10001 and end with MC30001. Then they turn out 800 spare RMC engines starting with RMC30002 thru RMC30801. Then they start back up with MC30802. This went on for the entire production run and all five contracts. So without any factory production records showing engine serial batches and their datas of production we can hardly even make a wild guess which engine number is correct for your jeep. Even if we had some factory paper on engine serial list of production dates we still have the issue with first in the warehouse from the foundry was not always first out.
Also both MC and RMC engines often found their way out the door to another venfdor who was building power units like the PE95 and compressors.