402 BB or 402 SB?

[chevy1969]

I have a friend that has a 402 BB motor just setting around that was given to him, he told me it was out of a 1970 chevy....I was a little confused when he said it was a BB, I thought that the 402's came as a SB......

Can anybody shed some light on this subject for me?

One more question, Did'nt chevy have the emblem on the fender that read 400, but it is actually a 402?

Any help with what is what on these motors would be great!!

[70c10]

I always thought it was a 396 BB that they called a 402. The cars had 400SB I thought. Somebody will correct me if I'm wrong.

[Smooth68]

402 is a BB, actually a factory bored 396. There is also a 400 SB

[CPNE]

The 402 is a BB, the 400 is a small block. The 402 is a factory bored over 396, first appearing in 1970 (in 68 and 69, BB trucks had 396's). The 400 badges on a truck indicate the 402 BB was installed, not a 400 small block.

[CPNE]

Heres a pic of a mostly stock looking 72 402BB. A 400 SB looks like a 350 for the most part.

[chevy1969]

So if I'm reading this correct, the 402 is a BB period even if it had a 400 badge on the fender, if it is a SB then it actually is a 400 and not a 402?

One last thing, which one is harder to come by and which one would you guys prefer?

Thanks again for all the info. !!

[CPNE]

You are correct.

Me, I prefer the BB. The 400 SB has a thin casting from what I've been told and is prone to overheating. You can build the SB cheaper than a BB. I guess it really boils down to what you application is and funds availability.

A lot of people must love the 400SB. I've had 2 and had no trouble selling them for good money

[Smooth68]

I think one of the main things that the 400sb is good for is stroking - ie 383.

[XXL]

Originally posted by CPNE
The 400 SB has a thin casting from what I've been told and is prone to overheating.

I believe the center bores are siamesed... and thus no room for water jackets through there.

Kenneth

[CPNE]

Yup, that's what I was referring too. Here is more info:

The next major milestone in terms of performance was the introduction in 1970 of the 400cia block. This deviated from the standard format in many respects. First, it used a nominal 4.125in bore, as opposed to the 4.000in bore that had become the norm. To achieve the 4.125in bore, some internal casting core changes were necessary. The most obvious external change was the use of three freeze plugs in the side of the block. To accommodate this larger bore size, the bores were siamesed; there was no water between the cylinder bores because the barrels joined in the water jacket. In contrast, all other blocks have water completely surrounding each cylinder bore. Along with this change in the bore size, the 400 motor was equipped with a 3.750in stroke cast crankshaft. To get this bore & stroke combination within the confines of the standard 9.025in crankshaft center to block deck height it was necessary to shorten rod length if the stock piston ring package was to be retained. The standard 5.70in rod was then shortened to 5.56in.

[stllookn]

The 400 small block can be built out to 468 ci using the Rocket block. They are desireable because the heating problems are vastly overrated and you can get great power without changing everything under the sun...brackets, motor mounts, header size etc. I think those extra cubes come in handy when your are trying to spank your buddies wheezebag 350...LOL!

[chevy1969]

You guys are the best!!!!!!!

Thanks a million for all the info.

[STP67-72]

I have always been asked if the 67-72 trucks had 400 smallblocks. I have never heard of it before.

[hobby67stepside]

I think the SB 400 was introduced about '75 or so.

[lukecp]

The 400 SB wasn't an option until sometime after '73.