I’m probably not describing it correctly, it’s the hole that lines up with the pressure hole out of the timing cover. The cover discharge is typically 1/2 inch as far as I’ve seen, wondering the corresponding hole in the block. My block is at the machinists. Thanks
I’m sure JW addresses that in the oil mods thread. https://www.v8buick.com/index.php?threads/400-430-455-block-id-prep-and-oiling-mods.214613/ Post #4 71 and up blocks should already be 5/8”, but you can radius the hole.
Yes, the suction hole is 5/8. Best I can find the oil under pressure from the pump, through the timing cover to the block is 1/2 inch
Suction hole on the mid 71 and later blocks is 5/8. This started with casting number 1248861, and was introduced into production in mid 1971.. I have seen documentation that suggests this was around mid January.. All 1231738 455 blocks produced for the 70 and early 71 models, had the 1/2" suction hole, including all 70 and the early 71 Stage 1 Engines. The Stage 1 engines were supplied with a 5/8 pickup tube, bolted to the block with a 1/2 suction gallery. The pressure inlet on the front of the block from the pump on all BBB's is 1/2" JW
