Stamped letter on bottom of block

[xring]

I've been cleaning up my '72 340 block while waiting for my pistons to come in before sending it to the machine shop. I noticed 8 stamped letters; some A's and B's and one C; on the bottom of the block - where the oil pan would be bolted. The letters roughly correspond to each cylinder. Any ideas what the letters mean?

Thanks.

 

[mopar head]

I`m not sure about 72 but if it`s a #`s matching block to the car some of your vin. #`s should be the same. Same goes with a 4 spd.8)

 

[MVRCorp]

Damn, I hate getting old. I heard about this years ago and just can't seem to access that lobe right now. This is going to bug me all night.


Damn!

 

[Mrmopartech]

There are 4-5 stamping letters they use for installing pistons.Each of the letters is a code for a piston that will have the final piston to wall clearance in ten thousands of a inch.For every bore after checking the bore a number is given and a letter is stamped to the oil pan rail to show the installers the proper piston assembly to install.If we use a 440 bore of 4.320,and the bore is measured at 4.3202,you would get a C,for two tenths over sized,and the matching piston is just a slight bit bigger at the piston skirt,getting the correct piston to wall clearance.This system allows for under and over bore cylinders,as the rod assemblies are in a large 5 foot square bin and thousands are in there,and there is a bin for each letter.mrmopartech

 

[xring]

Awesome info! Thanks!