[GOPAPA]

[QUOTE=70cst;3845663][COLOR="Blue"]The official difference between the 396 and 402 BB according to the Feb, 1970 Chevrolet Dealers Memo


My thoughts on this is about the same as others . Some very good reading here ,,thx for this posting beings I have a 402 out of a Chevellle ..

The 402 is a big block chevy, Chevrolet bored the 396 .030" larger to make an honest 402 cubic inches.

I read somewhere that the Core Shift during the casting of the blocks lead to an overbore correction. I also read that all Big Blocks were made in Tonawanda NY for fours years straight. All 402 began life as 396's made at Tonawanda.

Emmissions had a big part in why bigger discplacement engines were required to follow slightly less requiremnts than smaller engins. 400cid was a cutoff for the tougher requiremnts.

It was not good for sales for GM to change the badging from 396 to 402 because of the popularity of the 396.
GM wanted to make more power for more sales and found that a 402 gave a little more umph using off the shelf parts but the "402" was not the "396" so they opted to leave the name the same considering they are identical (almost).

With the exception of the 402 having a 030" larger bore, there is very little difference in power . I read that you can only tell the difference by a dyno test.

gp my