I've tried to dig up some "official" original factory documentation on the 396/402 change, but came up empty. I remember seeing/reading something years ago, and the reason stated in the article discussing the 402 (396ci +.030") was to produce a more favorable bore/stroke ratio in the pursuit of reduced emissions.
Back then, emission controls were in their infancy and the OE's were trying lots of different methods to help them mitigate the expulsion of unburned hydrocarbons into the atmosphere. Playing with bore/stroke ratios was one of them. Some of you may also remember the 307 small-block, which was contrived by combining the 327 stroke and a 283 bore. It, too, was an experiment in emissions reduction. Getting back to the 402, it was first introduced in late-production '69 Chevelles, and the easiest way to ID them is the addition of a "C" prefix to the engine code stamped on the front of the engine block. For instance, a "normal" 396/350hp/4spd Chevelle engine would have a "JC" engine code, while the 402 version of the same engine would feature a "CJC" stamping on the front of the block. The addition of the "C" prefix carried over to the '70 and subsequent engine codes. To the best of my knowledge, the 402 supplanted the 396 in all '70 and later Chevys. As for retaining the '70 SS396 moniker (even though the engine actually displaced 402ci), that was a marketing ploy pure and simple. Since it's inception in '66, the SS396 just kinda rolled off the tongue easy and became synonymous with Chevy high performance. Understandably, Chevy was reluctant to give up the equity they had in such a catchy name and kept it as long as they could. In '71, however, the Super Sport with the 402ci big-block was referred to as merely an SS, and the "396" emblems that hung below the SS badges on the fenders were eliminated as well. Please feel free to add or edit my recollections if your differ from mine... Chuck on 6/16/05 11:14 AM, Clint Hooper at [EMAIL PROTECTED] wrote: > Gene is correct and brings up a very good point; why did GM increase the > displacement to 402ci? > Maybe Chuck Hanson or someone else in the know can shed a little light on > the subject. > Clint Hooper > H&H Custom,owner > 1969 El Camino ProTourer > 2001 H-D FLHR custom bagger > http://dalesplace.com/misc/friends/clint/clint_hooper.htm > ----- Original Message ----- > From: "Gene's General Restoration Parts" <[EMAIL PROTECTED]> > > >> Hi, >> What I remember is up to 69 it was a 396 and after 70 the bore was >> increased .030 which made it a 402 but was still badged and called a 396. >> Some cars like the Monte Carlo and I think full size it was refered to as > a >> 400 Big Block and they also had the 400 Small Block to make it more >> confusing... >> I don't know why they went .030 over, maybe they had a bunch of blocks > they >> were able to rework with the over bore? Anyone know why they went .030 > over? >> Gene >> www.genesgeneralrestorationparts.com > > >
