1939 Plymouth 230 cid engine?

[Pete]

Hi all,

 

There appears to be an unusual situation with my flathead six. My '39 Plymouth was manufactured in Detroit and has a 23" head. The build card indicates that this engine was installed at the factory. The engine serial number is P8 (star) 347550 (star). It should be a 201 cid (3 1/8 inch bore). It has been bored to 218 cid (3 1/4 inch bore). This may have been done at the factory. The engine is currently at the rebuilder who found some interesting things after disassembling and measuring the block and components. Here is what I think may nave happened:

 

I've read that the second star in the engine serial number indicates factory modifications. I've also read that Plymouth would pull blocks off the assembly line that had imperfections in the bore, and would typically bore them a bit oversize. They put a mark on these blocks for the engine assemblers down the line, but I don't recall what or where that mark was.

 

There is a sleeve in the #6 bore. If it was installed at the factory (hence the second star), that might account for the overbore to 218 cid. All cylinders were bored to 3 1/4 inch. All cylinders were bored again by just .005 inch, probably after the sleeve was installed. A .005 inch bore is so small you hardly hear of it. Best guess is that was done to clean up the sleeve.

 

There was some engine work done about 1950, but the rebuilder says that the sleeve and related boring were done prior to that, and the 1950 work was only on the crank (turned).

 

So, if my speculation is correct, I seem to have an original Plymouth 1939 engine that came from the factory with 218 cid. No problem with the overbore -- after all, that's what Dodge was delivering with the same block that year.

 

I'm interested to hear what others think may account for this situation.

 

It's interesting how good the condition of this engine is. There is surprisingly little internal wear. The crank, main bearings, lifters, cam, and all but one valve will be reused. The brass water distribution tube looks almost new. The crank will be balanced. Of course all new pistons, rings, etc. as the block will be rebored a bit to clean it up. Before disassembly the compression, vacuum, idle, etc. were pretty good. The original intent of this rebuild was to clean out the galleries and water jackets, address leaking gaskets, seals, freeze plugs, etc., as well as a general freshening up. The head is going to get shaved a bit to increase compression. I'm getting the transmission rebuilt too.

 

I'm looking forward to driving the car next spring.

 

Pete

 

 

[Andydodge]

Pete, sounds like you have the gold standard in Plymouth engines, I've not heard of a brass factory water tube but its something that they all should have had........andyd.... 

[desoto1939]

I have a brass water dist tube as a spare for my 39 Desoto and this is the 25 inch long one. most were the galvanized style.

 

Rich Hartung

[tom'sB2B]

Of the 5 flatheads that I own, I have only found one with a brass distribution tube. The brass one came out clean as a whistle, while the galvanized ones were a bear to pull and we're heavily pitted.

[Plymouthy Adams]

the second star at the end only signifies the end of the number sequence....all Mopar of this era share your second star..only in the year 1954 where Plymouth had a optional engine size was there a stamp to denote this larger engine and that was a Diamond on the prefix stating it a 230 CI engine...in 55 the 230 was then the only available flathead 6 and thus no more special stamping other than the model prefix...Chrysler stamped all other engine codes relating to under/over on the components themselves...