Mu$tang

428 block date code 5j14 has 428 cast in rear water jacket floor but has a perfect X scrached in back of block ? any ideas

Attached Images

428 001.jpg (140.0 KB, 14 views)

CatSkinner

Near as I can figure is the "X" in the casting made it a service block. Basically, it didn't originate in a car, but sold or used as replacement. Don't take it as gospel, that's just the most common explanation I can find.

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Mu$tang

Thank's, I believe your right.

FFR428

I don't think that's a service block and here's why....... 66 was the first year for the 428. The date code on your block is 5J14 which is 65-Sept-14th. As 66 production started in July-Aug 65 I'd say it's a pretty early 428 block.