402 Question
 

Was The 402 Bored Out From The Factory? If Not Then How Does It Get The Extra 6 C.i.'s From The 396?

The 402 is a factory .030 over bored 396...


Chuck

Yea, the reason for this was due to some bad cores they had. They bored them .030 over to clean up the bores and still use the blocks.

no theres a lot of myths about why the bored the most logical and most realistic is because of the 400 small block gm didnt want a small block that was bigger than a big block it doesnt look good so they bored em out. theres other stories about a flood from a fire sprinkler all kinds of neat stuff

I read somewhere that Chevy did it to pick some of the lost HP from new emission controls-but they still called it a 396 in the Chevelles, but my 72 Burb had 400 emblems on it.

Reason they used the 400 emblems was to appease the insurance companies. They were also under-rating many of the musclecar engines at that time.

And they called it a 396 in the performance cars becouse the 396 had already earned respect.
I agree with cableguy, I think it was inner corperate politics. If you were to look into it, (IIRC) the 400 small block is also a 402...which if this is true, it would just back up the numbers game they may have been playing on the big block verses small block.

FYI They didnt start to make a 400SB till 75 I think

my sb400 came out of a 73 caprice. i know when they are bored .030 over the actual c.i.d. is 407 but i have never heard anyone call it that so 406 it is

Small Blocks
265..........3.750 bore X 3.000 stroke...265.0
283..........3.875 bore X 3.000 stroke...283.0
302..........4.000 bore X 3.000 stroke...301.7
305..........3.740 bore X 3.480 stroke...305.8
307..........3.875 bore X 3.250 stroke...306.6
327..........4.000 bore X 3.250 stroke...326.7
350..........4.000 bore X 3.480 stroke...349.8
400..........4.125 bore X 3.750 stroke...400.9



Big Blocks
396..........4.095 bore X 3.760 stroke...396.1
402..........4.125 bore X 3.760 stroke...401.9........the big block is bigger .010
427..........4.250 bore X 3.760 stroke...426.7
454..........4.250 bore X 4.000 stroke...454.1

I know that there are others.......mostly insignificant though.

I am currently looking into building a "backward of GM's way" 427 by using a 454 crank 4.000 and a 402 block 4.215 ...427.6. Thus being a stroker 427 rather than a big bore 427. I have yet to mock the crank up to see if I have rod clearence though. The 402 block is different near the bottom of the bores, so I'm not 100% that this will work.
BTW, has anyone done this? does it in fact work?

The 400 small block was made from 70 untill either 79 or 80.

Looking thru a GM Tune Up manual;specs are listed for the 400 engine for the following years.-- Chev auto- thru 1976; Chev/GMC trucks- thru 1977; Olds- thru 1975 and Pontiac thru 1978.

Through a year doesn't help... because we need to know what year it started in!

And I guarantee that it wasn't around in 1940. ;)

Had A stock originial 1970 Monte carlo with a small block.. 1970 was the first year

Hmmm, acording to the red book, the chevy trucks could be had with a 400 untill '80.