1973 351C-4V Block Casting Letters

[Steve73QMach1]

Back in 2004 when I had my engine apart on my Mach 1, I saw these weird casting letters near the lifter bores. Is this normal? Any idea what this signifies?

 

[mjlan]

Those marks are usually mold repairs in the foundry. When the block molds age and get weak, they get those marks to increase the strength of the mold in those areas.

 

[Steve73QMach1]

That's interesting - I hadn't thought about it from that perspective. These marks are on all four corners. This photo shows another side:

The block has these numbers:

 

[Jeff73Mach1]

I've seen them on multiple blocks. I was under the impression they were to assist with directing oil back to the returns