Let's decode my block

[Rustychucks]

Hey there, Ive been lurking in the shadows for some time now. Probably introduced myself about a year ago. Since then Ive used the site for a lot of great reference. I was hoping someone could decode my block for me. The engine stamp is  (Diamond)P25(Star)4075 i5(Star). I also just busted a lower front shock stud so some advice in that arena would be great as well. Hope you chaps are getting on in a delightful fashion. Thanks in advance. Mike

[Plymouthy Adams]

diamond denotes1954 only stamp to identify the mid year change to 230 cubes from 218...55 and forward was 230

[Plymouthy Adams]

PS..the capital letter "I" denotes a numeral one by the way...as in Roman numeral

[greg g]

Based on the pic in the avatar, your engine is a swap in from a 54 Plymouth, making it a 230 instead of a 218. giving you 13 additional HP over the 97 for your cars original engine. in addition tot he extra cubes, you also have a higher compression ratio. up from 7 to 1 to 7.25 to 1.

[Rustychucks]

I really have no way of knowing if it is a 218 or a 230? What does the roman numeral 1 mean? Its all so mysterious.

[TodFitch]

I really have no way of knowing if it is a 218 or a 230? What does the roman numeral 1 mean? Its all so mysterious.

 

Lets see if I can answer that. Oh, yes here it is:

 

PS..the capital letter "I" denotes a numeral one by the way...as in Roman numeral

 So your engine number should be read as (diamond)P25*407515*

 

Regarding if it is a 218 or a 230, here it is:

diamond denotes1954 only stamp to identify the mid year change to 230 cubes from 218...55 and forward was 230

 

So you have a 230. As answered in the first two replies to your original question.

 

(Sorry for the somewhat over the top answer, but Plymouthy Adams answered you directly at the beginning of the thread.)

[JohnTeee]

Here's a very nice reference site that may answer the question: Flat Head Six Engine Numbers That Start With "P"

 

P25 218ci   Plymouth Car Plymouth 6 1954

 

Except that site does not address the 'Diamond' stamp . . .

 

Cheers!

 

John

Edited April 3, 2014 by JohnTeee

[greg g]

If you want hard visible proof you can measure the stroke. Over cylinder #6 is a square pipe plug in the top of the head. Removing this gives you access to be able to insert a length of stiff wire. Turning the engine over by hand will allow the wire to travel with the piston from TDC to BDC allowing the stroke to be measured. 4 3/8 =218, 4 5/8 = 230. Obvilusly the wire needs to be more that 4 5/8inches long to do this. Don;t forget to replace the plug when finished.