Quote:
Originally Posted by tanksteve
The casting number says it is an early 1971 455 HO block as the seller claims. The YC code makes one suspect it is a dealer stamped service replacement block even though we cant see the sr on the EUN number. Or somehow the factory ran out of 2 bolt main 455 blocks on that day. Rocky Rotella is probably the best expert on early 455 blocks..
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Wrong. Not an early '71 HO block. Same casting number was used on all '71 Pontiac 455 blocks cast between early Gxx0 & 1100. Have mentioned before, I've owned an early Gxx0 dated YG 455 that was mistakenly factory machined/assembled with 4 bolt caps. Some '70 model 455 YH code blocks were also misbuilt with factory 4 bolt caps. Having the outer bolt holes in the block drilled & tapped then assembled with 2 bolt main caps does not make the block a factory 4 bolt block.
71 455 casting numbers.... Pete's book 33 years ago listing the 485428 casting number as "late" '71 455 HO is the source of that.