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

[70cst]

Interesting thread ...

[C20-67_N_MO]

Originally Posted by 70cst

Interesting thread ...

That's putting it midly.

It is indeed interesting to see everyone's point of view on this subject. As it seems we are not closer to answering the question at hand.

As the answers sound more like theories than reavent facts.

[leddzepp]

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[70cst]

Originally Posted by leddzepp

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I knew the horse would show up

[1972RedNeck]

I would just tell a person my truck came with a 396. I bored it .020 over and got the fender badges. Then I bored it another .010.

[70cst]

Lets say the 402 is the Covette version of the 396 which makes it a Corvette Optioned truck Just a thought

[VA72C10]

Originally Posted by 70cst

Lets say the 402 is the Covette version of the 396 which makes it a Corvette Optioned truck Just a thought

[67_C-30]

Originally Posted by 70cst

Lets say the 402 is the Covette version of the 396 which makes it a Corvette Optioned truck Just a thought

Well, technically the 402 was only part of the ultra-rare Super Corvette Option (RPO#OU812) with the HI PERF Ambulance Engine as well. If they were equipped with 4.10 gears, they came with the hood mounted antenna. GM had to do this because the HI PERF Ambulance Engines that came with the Super Corvette Option had so much torque that the antenna mounted in the stock location would break the windshield on hard launches. The standard Corvette Option came a HI PERF 350. There were some Ambulance Engines special ordered through COPO in standard plain jane C-10's, but these are like finding a Hen's toothbrush.

[gcottingham]

It was actually just marketing. There is no difference in the bore or otherwise. Think about the motorcycle market. They always fudge the cc to something that makes sense or keeps up with the competition. The Ford engineers were winning, so GM played a few tricks from year to year while they were in development of better engines. It was easy to fudge from 396 to 402 at a time when they were introducing the 400 small block. Workers on the factory floor were given liberty to liquidate emblems in batches. As long as they were in line with the models produced. There were no ISO standards back then. Just well kept factories.
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[leftybass209]

Originally Posted by gcottingham

It was actually just marketing. There is no difference in the bore or otherwise. Think about the motorcycle market. They always fudge the cc to something that makes sense or keeps up with the competition. The Ford engineers were winning, so GM played a few tricks from year to year while they were in development of better engines. It was easy to fudge from 396 to 402 at a time when they were introducing the 400 small block. Workers on the factory floor were given liberty to liquidate emblems in batches. As long as they were in line with the models produced. There were no ISO standards back then. Just well kept factories.
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This was the way i always understood it. There is a lot of "mystery" surrounding the 396/400/402 engine. I would love to hear if someone actually cracked open a "402" and compared it to a "396" from the year prior. It's easy to input the numbers in a calculator and say the bore should be 4.124 inches compared to the 396 with a bore of 3.094 inches. Consumer consumption was the determining factor in how these engines were badged. I honestly couldn't see Chevrolet boring out all their 396 motors for any reason. They would not have bored out engines, being untested and unchecked just because of flooding. R&D did indeed go into their products before the idea of quick fixing some castings, even during factual problems they had. The flooding stories and casting problems all seem to be myths as everyone knows someone who worked at Chevrolet during the times when records and facts were at their least, and none of the stories coincide. The engines may indeed be different bores, but we will never know the real reasons for sure.... until someones grandfather who was Zora Duntovs best friend personally oversaw the entire operation.

[leftybass209]

To further ad, it was commonplace for people to say the 302 was built with off the shelf parts to fit into the scca rules of 305 cubic inches. The crank was NOT just a 283 crank off the shelf. Maybe for R&D purposes it was stuffed in, but the crank in an actual 302dz engine is different than that of your 64 Nova, or C10, or anything else that had a 283. I did a lot of research on that motor as I wanted to replicate one and put it in my 69, until I found it was just not a safe reliable motor to use in a DD or even a weekend driver. Also, it's hard to believe there were any actual changes to the 396 castings when Chevrolet was so honest about the horsepower and torque numbers these motors produced!!!! All these stories sure are informative and entertaining though! Love hearing it all as I wasn't alive during the muscle car era.

[GuyO]

Originally Posted by LONGHAIR

I have heard the flood thing before too, but I'm not so sure that I buy either of the "damaged" block theories.
If the bores were rusty, the rest of the block would have been too, lifter bores, main saddles, etc...
If the bores were "crooked" they would have gone back to the supplier....

They couldn't possibly have been "sitting on" that many blocks. If that really had been the case, they would have either used them and just said nothing, sent them back to be "recycled", held them as warranty replacements, etc. They would not have spent the time/money to re-bore them and create new pistons to make it happen. Plus, they would have gone back the "standard" 396 configuration when the "supply" of these "bad blocks" was exhausted.

I think the 400 in small block form was the issue. The smallest "big block" needed to be bigger. The 400 came out in the same year, coincidence?

Now why they used the 400 name badge for trucks? and 402 in cars? Who knows?

I read that the 400 badge was due to Federal emissions regulations prohibiting engines larger than 400 ci.

[CC69Rat]

What's a 60 over 396 ? 408 .. right ? Just thought one of you guys might know.

I think that's right. Kind-of a hijack, kinda not

[Longhorn 70]

I am so glad my 70 came with a 350 and the matching badges. Of course it needed the Olds 425 in it then bored .030" over making it 431 but I can't find 429 badges except on F***.

WAIT

Originally Posted by leftybass209

.... Also, it's hard to believe there were any actual changes to the 396 castings when Chevrolet was so honest about the horsepower and torque numbers these motors produced!!!! ......

Maybe I misread that.

[Ol Blue K20]

OK, my two cents. This is what I was told by a local chevy dealer who had had his dealership since the early 50's. It started with a bunch of flawed castings, GM decided to use this to their advantage in marketing a larger engine. They made 402 emblems for the vehicles but then California threw a monkey wrench in things with a new Smog Law. Any motor over 400cid had a more stingent smog requirement so GM decided it was easier to call it a 396 in the cars(use old emblems) and 400 in the truck. Cheaper to make a 400 emblem for the truck than put smog on it.

[LT4XTREME]

Originally Posted by dwcsr

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

I know I'm doing a fair comparision since I don't know the gear ratios but, dad has a 84 International S1700 with a 392 with only 38,000 miles and has had 2 70 C60 with 366 tall deck BBC and a 73 C60 with a 427 tall deck and a handfull of small block and straight 6 dump trucks. While the Int 392 is a good motor it's as slow as some of the straight 6's and has had lots of problems with the heads/valve train and always/always has exhaust manifold leaks and valve cover oil leaks. the tall deck BBC are work horses the have the slow torque to get the job done but when you need more they always seem to find the extra power your foot asks for. My favorite one was the 73 C60 427 TD BBC with 5 speed trans and 2-speed axle with a huge 14' aluminum Benson dump bed. Jason

[SKELLY4x4]

So my 72 K20 came with a 350. I pulled a BBC 396 out of a 69 C30 years ago, had it rebuilt to be a 402 and it's now in my K20. I went with the 8 396 repro badges. Will post pics when I get them installed. Could have bought the 8 400 badges but I figured folks would think it had a small block 400 which it doesn't have.