Posted: Thu Aug 15, 2019 7:32 am Post subject: Gen set with 641087 casting RMC engine?
The 641087 series block introduced under a test run in Jan 52 for 100 engines then finally officially started production in Feb 52. This block was erroneously labeled with casting # 641087 while it's blue print called for a new casting # 804380 but the production correction of the casting # at the engine foundry took place in May/Jun 52.
So if I'm reading this right, that puts my 641087 block with 10 bolt rear cast somewhere in the first six months of 52?
ETA: My apologies in advance for the slight hijack... It goes towards my understanding that my RMC block "may" have been installed new in a PE95-K genset, which is where I found it..as discussed previously here:
The order number on the genset tag ends in "51-11" which I've always taken as November 1951 (with no proof mind you). The SN of the genset is 3358, so that feels like it fits with a new engine which was produced in the first half of 1952...
Put another way, it seems unlikely a genset built in very late 51 or early 52 with a civy industrial engine needed an RMC motor pool replacement engine that was cast in the first six months of 52, unless that engine sat in storage for a considerable length of time
We split your post from the hijacked post and stood it here on it's own since it offered no related discussion to that post subject matter.
If your gen set was indeed delivered to the military Nov 51 it would not have had a 641087 10 bolt casting that was not introduced until Jan 1952. It would be more likely that your RMCXXXXX engine is actually a replacement engine installed in the Gen Set in the field. These factory spare engines for the military were stocked at the various military depots and only ordered for a field replacement when the original engine was unrepairable or downtime was not available to rebuild the original engine. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Order number 13104-PHILA-51-11, not delivery date.. I do understand what you're saying about stocking engines at depots... my assumption is that Onan signed a contract to deliver "X" number of generators and the 13,104th purchase order (issued out of Philadelphia?) in 1951 was in november, and it stands to reason it may have taken a while to build the 3358th genset at which point I believe RMC105103 would have existed... If the genset was delivered with a different engine then RMC105103 conceivably would have been in storage years and possibly decades.
You helped me in that I didn't know that the 641087 10 bolt rear block was a relatively short run that can be "dated" (because obviously an RMC block by definition didn't fall in line with any estimation of matching an ESN to an M38 SN, but only ESN sequence). Much appreciated.
I also did not know about looking for a machining date stamp on the oil pan rail when I had the engine open, so that bit will have to keep for another time.
Your order # does not match the format of an Army contract # so it is a bit obvious the order # is a civilian order to Onan which would have resulted in Onan assembling their civilian ordered Gen Set with a Civilian serialed engine which would have been a J serialed engine. RMC engine are engines built and delivered to the military under a military contract # and would not have been shipped during that short 5-6 month production period to anyone other that the military.
Here are examples of Military contract #'s from that period:
Hmmm... I'm finding order numbers of my format over on the "G", to the extent that I now think the "11" is likely the eleventh week of '51, not the month. Military or civilian number not as important to me as being able to pigeon hole the date...I'm certainly no expert. I still stumble across references to engine production diverted to industrial applications, but can't say they are authoritative sources... my default has to be it's a replacement, I just don't believe in coincidence, lol.
Your information on casting number and 10 bolt flange is more telling than 51-11, and a review of the M38 database shows the highest MC ESN in the mid 90xxx range, early june of 52... my understanding is MC and RMC engine numbers were sequential, so it looks like RMC105103 was numbered after m38 production to fill possibly the last contract (?) (most of the RMC numbers in the database are higher still) Correct me if I'm way off, but that seems to fit june 52 all around
- near the end of the 641087 10 bolt
- early on in a run of RMC blocks post M38
The RMC finding it's way into the PE95-K as a replacement only means it likely has less hours on it than show on the meter..."win"
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