the story that has been heard around the machine shops for years is that the
cores for the 396 castings
had wore-out and the .03 over size got the yield back to acceptable levels.
the other story that I have heard over and over is there was a misprint on
a blueprint for the new casting cores
with the same result .
Geoff
Right Foot Engine Shop
----- Original Message -----
From: "Chuck Hanson" <[EMAIL PROTECTED]>
To: "The Chevelle Mailing List" <[email protected]>
Sent: Thursday, June 16, 2005 6:33 PM
Subject: Re: [Chevelle-list] 70 ss only
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
