Strange 318 Block

George Jets said
I am betting it is a High Nickel content in the block cast mix. The chevy 350 guys want the 010 block that has the high nickel content for their performance builds. I honed one of these and the Cylinder Walls are really really hard.

A good simple test might be to see if it has very little ridge in the cylinders at the top compared to a regular 318 cast block that usually gets a pretty good ridge at the top of the cylinder after a lot of miles.

Will be interested to hear what you find out more on it. Pretty Unique !

All Chrysler blocks are made from the same iron. The race blocks use the same iron as passenger car blocks.

Second, I don’t know what that R means but by the looks of it the pan rail is not filled.

If it’s not filled it’s a run of the mill 318. Post some pictures of the main bearing bulkheads. That’s the quickest way to figure it out.