1962 - 1965 327 870 block differences?

[Peter M.]

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I understand that the Chevrolet block casting number for 1962 to 1965 327's generating 250 to 375 horsepower is 3782870. Taking away fuel management, rotating assemblies, and heads - are all 820 blocks structurally the same? In others words, without stamp pad coding as an indicator - there is no difference?

[Mike M.]

Re: 1962 - 1965 327 870 block differences?

all 870 blocks not the same. sometime around jan of 1965, the SIZE of the casing # was reduced by about 25%. i refer to the pre jan 65 870's as the "Tall" 870 and then the smaller came into production in or about jan 1965. i'm not saying a large 870 couldn't have been utilized after jan 1965 but i've not seen any genuine "Small" 870's prior to jan 1965. anybody else can chip in? mike mccagh

[Peter M.]

Re: 1962 - 1965 327 870 block differences?

Thanks Mike - when you refer to "size of casing #" you are just referring to the casting part number fonts I assume? I was most interested to know if the actual internal / external physical structure of the 870 varied ie webbing supports, main bearing supports etc. I have a 1965 870 block that was decked in a past rebuild and wondered if one could determine what its original configuration was without engine pad code stamp present.