Engine Block Stamp Marks? Flathead 134.

What is the significance of these letters stamped into the block next to each cylinder bore? (1952 L-134 M38, never rebuilt.)

From front to rear, "C - D - D - B" .

Piston ring fit? I feel as if maybe I used to know, but I don't remember.

Interesting marks on piston #2, also. (Ignore the raindrops...)

Thanks.

 

You

No first hand experience, but...used back in the day in matching mass produced pistons to mass produced bores.
Others, in the know, will need to agree or disagree regarding the 1952 L-134.

 

Dave is correct. After the block was honed it was measured, and marked with letters A - G so the person assembling the engine would know which pistons to use in each bore.

 

Thanks both. I was guessing something like that.

 

For what it's worth my 52 M38 is BCDC Sir #rmc113898 ? on the 8
Mine was rebuilt and needing another its now 40 over or just double the tag.
I told my machine shop don't hot tank it and don't take my tag. A 70 year old engine should look it to a point.

 

cool.

 

From the 3B Page:

• A: 0.010" undersized main and connecting rod bearings
• B: 0.010" oversized cylinder bore
• AB: both of the above
• C: 0.002" undersized piston pin
• D: 0.010" undersized main bearing journals
• E: 0.010" undersized connecting rod bearing journals

 

Where would that stamping be found? By the engine number, above the water?

 

On the deck of the block as shown in your picture

"From front to rear, "C - D - D - B" ."

Your engine has:

C - #1 meaning it is 0.002" undersized piston pin
D - #2 meaning it has 0.010" undersized main journal
D - #3 meaning it has 0.010" undersized main journal
B - #4 meaning it has 0.010" oversized cylinder bore

These stampings told the assembler/engine builder from which bin to retrieve the piston / rod assemblies and bearings.

 

I find that quite surprising for a "new" engine, being this engine has not been rebuilt.

 

It was what they did on the assembly line for building new engines, so it makes perfect sense to me to see those marks on an engine that has not been "rebuilt".

 

Understood. But surprising to me that a new engine would be allowed such variations.

 

Things were different in the 40s. There were no computers, and a lot of the machining, such as honing the bores, was not as precise, and some of it done by hand. What was precise was the finished product, which is why so many of these engines still run after 3/4 of a century.

 

Well, as Jaques Cousteau said "We must go see." Just measured, and all four cylinder bores same the same, possibly about .010" over.

Perhaps I misunderstood. In the comments above, I thought it was weird if just one cylinder or bearing was different. ( "...each bore..." )

Do these codes apply to all four cylinders equally, not just the one where the stamp is located? That would make much more sense to me, regarding "variations." But then, the main journals supposedly have two stamps... I'm confused.

 

3B would be an F head not the L head of the MC. I was told the numbers were for ring fitting.

 

You are correct, but it doesn't matter, the bottom end of both engines is the same, and also correct that the numbers were for fitting rings, and also piston pins, and bearing as already said.