Official Difference btween the 396 and 402 BB Because you asked.

[str82666]

1970 c10

[too much stuff]

Of course, 1970 was the "gray" year. I think it would be a 402. 68 and 69 are 396, and 71 72 are 402. You could get the casting numbers and front pad numbers and we could try to identify it for sure.

[str82666]

Oh it's not my truck, but I am curious because I have seen a few with the 400 emblem and didn't know which engine they had.

[str82666]

What about with the above discussion where the spec order sheet for the 1970 reads "L47 396 CU. IN. V-8 ENG". Could that still be a 402 eventhough it reads 396.

[70cst]

Originally Posted by str82666

What about with the above discussion where the spec order sheet for the 1970 reads "L47 396 CU. IN. V-8 ENG". Could that still be a 402 eventhough it reads 396.

Yes...it is my understanding that all BB trucks in 1970 came with 402 engines. My SPID tag reads that I have a 396 but it is a 402.

[67/72junkie]

starting in 1970 all 396 where changed to 030 from factory to make 402.030 396 piston is same as standard bore 402.This was done due to the fact that small block 400 was introduced in 1970 and gm did not want a sb with more cubic inches than bb.I have friend who collects chevelles. he has 1969 and 1970 SS396. Both have SS396 badges both are 325 hp 1970 is 402 but has same casting # on the block and both have 290 casting closed chamber heads monte carlo man 400 sb introduced in 1970 was hi torque motor and not considered hp at the time 515 casting 4 bolt block with 265 hp. With lt1 186 casting heads and cam it will make more hp and outperform lt1 but not from the factory. lt1 was 360hp in camaro and 370 in corvette

[70cst]

Originally Posted by 67/72junkie

starting in 1970 all 396 where changed to 030 from factory to make 402.030 396 piston is same as standard bore 402.This was done due to the fact that small block 400 was introduced in 1970 and gm did not want a sb with more cubic inches than bb.I have friend who collects chevelles. he has 1969 and 1970 SS396. Both have SS396 badges both are 325 hp 1970 is 402 but has same casting # on the block and both have 290 casting closed chamber heads monte carlo man 400 sb introduced in 1970 was hi torque motor and not considered hp at the time 515 casting 4 bolt block with 265 hp. With lt1 186 casting heads and cam it will make more hp and outperform lt1 but not from the factory. lt1 was 360hp in camaro and 370 in corvette

Good info.
From a marketing perspection that does sound logical and makes sense.
Thanks

[rbagley]

I've heard that they kept badging the 402's as 396's because the 396 was so popular and people don't like change as much as 6 c.i.

[70cst]

Originally Posted by rbagley

I've heard that they kept badging the 402's as 396's because the 396 was so popular and people don't like change as much as 6 c.i.

Its my understanding that for trucks...from 1970 and on they were badged 400's.

[rbagley]

Originally Posted by 70cst

Its my understanding that for trucks...from 1970 and on they were badged 400's.

Good point

[70cst]

WOW...I am watching "Whats My Car Worth" ... and they said that up until 1969 GM put out an edict which said no intermediate car could be bigger than a 400. Then in 1970 this edict as lifted. Interesting.

['72customdeluxe]

The "imperfections" in the blocks story sounds weird, I thought the water jackets were different.

[Pickupmanx2]

Originally Posted by 70cst

Its my understanding that for trucks...from 1970 and on they were badged 400's.

Mine is badged 400,,,, glove box says 396,,,, NAPA books for 70 are 402,,, I don't even want to think about going to kragens,,,,, "but our computer says...."

[basemodel67]

Originally Posted by 70cst

WOW...I am watching "Whats My Car Worth" ... and they said that up until 1969 GM put out an edict which said no intermediate car could be bigger than a 400. Then in 1970 this edict as lifted. Interesting.

That is correct, well, mostly. From the factory, all A-bodies were limited to 400ci, but outside sources weren't limited to how big of engines they installed. Hurst installed 455s in Cutlasses in '68 and '69, Yenko put 427s in Chevelles (or COPO'd them that way), and Royal was dropping 428s in GTOs. Then in 1970, the edict was lifted, and the rest is history... SS 454, GS 455, 442, and GTO all used the new CI freedom to create some of the greatest cars of the musclecar era!

[Rat Bastid]

i have a 71 cheyenne super the SPID says l47 400 ci v8 and its a bigblock 402 so i am totally confused

[67/72junkie]

you could get intermediate with bigger than 400 cubic inches before 1970 COPO Central Office Production Order I know they had copo 427 camaro

[lovnthe70]

I personally think there was a conspiracy between two guys sitting in an office having a little whiskey in their coffee one morning when one of them said to the other " you know what would be funny John" "whats that Bob?" "lets turn this 396 into a 402 and then badge it as a 400……. then when the internet comes out we can sit back and laugh at all the enthusiasts who try to figure it out!!!!! ” “sounds good Bob…. Lets get to work”

[70cst]

Originally Posted by lovnthe70

I personally think there was a conspiracy between two guys sitting in an office having a little whiskey in their coffee one morning when one of them said to the other " you know what would be funny John" "whats that Bob?" "lets turn this 396 into a 402 and then badge it as a 400……. then when the internet comes out we can sit back and laugh at all the enthusiasts who try to figure it out!!!!! ” “sounds good Bob…. Lets get to work”

[dwcsr]

Originally Posted by D-Rat

The old IHC 392 might only show as 236hp, but I bet it has the lowest torque curve of all the engines there.

I worked for IH for some years and the 392 was a far better truck engine than a 400.

[Pickupmanx2]

Originally Posted by lovnthe70

I personally think there was a conspiracy between two guys sitting in an office having a little whiskey in their coffee one morning when one of them said to the other " you know what would be funny John" "whats that Bob?" "lets turn this 396 into a 402 and then badge it as a 400……. then when the internet comes out we can sit back and laugh at all the enthusiasts who try to figure it out!!!!! ” “sounds good Bob…. Lets get to work”

See,,,that's EXACTLY what I'm talkin bout!! Good one!!

[70cst]

Originally Posted by dwcsr

I worked for IH for some years and the 392 was a far better truck engine than a 400.

I am not disagreeing but...why was the 392 considered a far better engine than a 396/402? It seems the 396/402 in todays hobby is the engine if choice.

[68caliRat]

I'm kind curious about all this info being correct. I have a a "396" in mine, and it's been the same engine since my family bought it from my dad's friend in like 76. Mine has the spin on oil filter, so now this makes me think it could be a 402?Hellz bellz, I know it was rebuilt at some point before my father got it. Napa seems to be the only auto parts place to give me the correct filter for it. The others try to give me a canister type filter. This makes me think the engines were swapped during the rebuild...

[orange_classicbowtie]

This is what I got from my grandfarther years back .The 402 was a bored out 396 replacement engine CE block.It was a defect in alot of block castings as to what I believe monte0185 and leddzepp explained very well.The motor division was running short of replacement warranty engines to the dealerships.So the returned stockpile of returned engines were rebuilt 30 over and sent out as replacements..and to factories for new installationThe motor C.I. allowed by automotive safety at the time was 400 C.I. thus being the fender designation not the true C.I. of said motor.Later that year blocks were being casted as a 402 standard bore not a bored out 396, which now give the engine rebuilder to inlarge block 60 over.....I hope this made any light on to this uncertain confusion...

[70cst]

Good info all...but I am guessing there will be questions to the whys until the end of time.

[Walts_restoration]

Originally Posted by Rat Bastid

i have a 71 cheyenne super the SPID says l47 400 ci v8 and its a bigblock 402 so i am totally confused

In 1970 they had two 400s as i have heard the tale, the bored out 396s .030 over, and the 400 small blocks. People at parts counters were going nuts trying to figure out if they needed big or small block parts, and confusion ran amock. So to counter, gm changed them to 402s in 1971 in order to keep people from getting confused and what not. As to the 400 emblem, that would explain the 400 on the fenders but a bbc under the hood, they were just to lazy to make a 402 emblem i assume.