rookie engine question

[homer41]

Are there identifying marks on plymouth or dodge flatheads to easily tell them apart?  Dave

[knuckleharley]

Yes. The first 3 images in the engine serial number stamped on a boss up near the head and the front of the engine. For example the letter P means Plymouth,D means Dodge,C means Chysler,DE means DeSoto. There will be two numbers behind the letter to let you know what years/series the engine was originally installed into.

[homer41]

So to the untrained eye there really is nothing jumping out to tell engine cid. Or make. I understand the 23. 25 " thing.   Dave

[B-Watson]

DeSoto was "S".  The letter follwed by a number was used from 1936 through 1957.

If the number ends in a "C" it is a Canadian engine built starting in mid-1938 and is a 25" block.

P and D engines, with no "C", were 23" blocks.   S and C were 25" blocks.  

Bill

[knuckleharley]

55 minutes ago, B-Watson said:

DeSoto was "S".  The letter follwed by a number was used from 1936 through 1957.

 

I stand corrected. Thank you.

[knuckleharley]

1 hour ago, homer41 said:

So to the untrained eye there really is nothing jumping out to tell engine cid. Or make. I understand the 23. 25 " thing.   Dave

Yes. The number after the "P". It tells you what series the car is.

[homer41]

My question is, unless you read the engine serial # you have no idea of cid or manufacturer.  Is that correct?  Dave

[ptwothree]

Also, the date the block was cast is located between the distributor boss and the pan rail....at least on the two blocks I have.

[B-Watson]

6 hours ago, homer41 said:

My question is, unless you read the engine serial # you have no idea of cid or manufacturer.  Is that correct?  Dave

That is correct.  The engine number is easiest way of determining what you have.  The date the block is cast can tell you nothing more about the engine..  The engine number can tell you the make and model using that engine as well as the model year and the engine size.  In the 1960's Mopar engines also had markings such as "HP" (high performance - 4bbl carb) and "MP" (maximum performance - multi carbs set ups, ram induction, etc.).  Other markings include variations in internal parts (main bearings, cam bearings, etc.) that can help in restoring the engine. 

BIll

 

[dpollo]

Here are some less obvious signs of a block's vintage.   By the late 40s, the oil pressure regulator used an 11/16 square headed plug rather than the earlier hex.

Blocks after 1953 had an extra  gusset cast in to support the Powerflite This has an extra bolt hole  facing out from the pan rail about 8 inches from the back of the engine.  These engines  also had casting bosses which may be drilled for Hydrive and Powerflite engine  fed torque converters 53-4. From 51 onwards except for some Spitfire (Chrysler 251) blocks there is an extra water passage at the front of the head. This is an internal bypass to eliminate plumbing between the water pump and thermostat housing.  On Canadian enginess, heads after  '51 have the DPCD logo in a circle  near the firing order.  Canadian blocks did not have the date below the distributor.

Often, when blocks went through  a factory rebuilder like those supplied by "Chrysler Method" shops,  the year the block was cast was not important as long as it had the features required for its intended use. 

 

[Skrambler]

But, maybe to answer his question:

No, if you lifted the hood at a car show, 8 out of 10 people would not argue that the motor they see sitting in there was not the one that it was born with.

[Dan Hiebert]

...and 9 out of 10 enthusiasts, even, can't tell just by looking.  Not without leaning over the fender to look at the engine number or to nit-pick. 

[Eneto-55]

I don't know when these changes took place, and these are attached parts, not the block itself, but by 1955 the temp sending unit was electric, and the head has a smaller tapped hole.  Narrow belts. The exhaust exits at a different point on the manifold.  Probably other small details as well.

[homer41]

Just exactly what I wanted to know, thanks.  Dave