I'm rebuilding one of my three aluminum block engines and I'm puzzled by
the big grease pencil letters on the right-hand side of the engine. They are different on each engine B..C..C..E..ect. My machinist thinks that the factory must have sized each piston to its bore...I haven't found reference to these markings in any of the excellent articles posted here. Is this what
they represent? Did I miss it somewhere? Just curious..

Thanks,
Steve

Yes, the grease markings on the sides of each cylinder is to match the piston to the actual bore size.

The way it worked was that the block machining line would hone and measure the bores, then write the letter code on the side of the block.

The block would then go to the engine assembly line where the pistons would be pulled from corresponding "lettered" bins. (the pistons were measured and sorted into the bins by size)

This process allowed for a wider tolerance range on the parts with-out the risk of getting a too loose or too tight combo installed, due to tolerance "stack-up".
DD

Nice!

Ive got a Yale forklift at work with an IND-30 flathead six that has these letters stamped on a boss at the front left side of the block, I was wondering what they meant. Right on!

_________________
I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

Thanks for the info, its interesting to learn about the way these engines (and apparently some others!) were produced. One of my aluminums is
original (I think the head gasket was replaced) and it doesn't burn any oil
whatsoever! Best guess is 130k+ on it. Careful assembly is the secret to longevity.