[IRELAND EXHAUST]

I just got a 396 to put in my 68 swb chevy. It has 30 over cylinders except one is 40 over. The cylinders are good and clean and don't need rebored, but should I punch the rest of them out to 40 over or leave it. Also I am looking for suggestions on how to build the motor. I am looking for lots of low end up to about 5000 rpm, but also wanting to keep it very streetable. I am also thinking of aluminum heads, so any suggestions or ideas is appreciated. The block is a 1967 and the steel heads I have are off a 1974 big block.

[68NovaSS]

Geezus, have the other cylinders bored. I can't guess your level of experience, but you know you don't simply take it to the shop and tell them to bore it .040, right? No reputable shop would accept that. Take the pistons with, the machinist will hone to the clearance you specify or piston requirements.

[F&J]

I would bring it to a shop, too. "IF" the rest are really good, it may be possible to sleeve that one and bore it to 30 like the rest?

[Chevrolet4x4s]

I would punch the other 7 .010'' over. Is it possible that you have a 402 block with one excessively worn cylinder? The 402s were a 30 over 396 , and were marketed as 396s,400s,and 402s.
Shane

[68NovaSS]

When did GM ever market a 400 BB??

[F&J]

Yes he's right. I don't recall what year,but GM DID call it a 400 engine for a very short time. I am positive about that.

I don't remember if it was in sales info or whatever. I do remember that I thought is was very confusing with 2 400's a bbc and sbc.

[rreruption]

at some point in the mid 60's a little after they came out with the 396 I think in 1970 they changed it to a 402 so they could claim a 400 plus cube engine for advertising rights.
try doing oval port heads L29 vortecs
http://www.sdparts.com/product/10141...nderHeads.aspx
some roller rockers,a small cam something in the 218/224 to 224/230 duration range
a performer or cylclone intake
and a decent rebuilt q jet

[IRELAND EXHAUST]

Seems as if I bothered some people and the first reply is exactly why I hate to post. The pistons I pulled are marked and one piston is 40 over and the other 7 are 30 over. Why this was done is beyond me, but it was!! I am not a pro as some of you evidently are on here and I asked what I thought to be a reasonable question. But I can guarantee one thing this will be my last, looks like you guys need moderators with a little more finess!!!!!!!!!!!

[heyjude076]

Originally Posted by 68NovaSS

When did GM ever market a 400 BB??

This partial list of block casting # was taken from http://www.mortec.com/bbc.htm

Note the 402 block in 70 - 72. Would the build date signify a factory 402 vs a bored 396?


3946052....427.......69......4-bolt, Alum. ZL-1, Mark IV
3946053....427.......97-up...4-bolt, Alum. ZL-1, 2nd version, Mark IV
3955270....427.......69......2 or 4 bolt
3955272....396.......69......2 or 4 bolt
3955274....366T......68-85...4-bolt
3955276....427T......68-73...4-bolt
3963512....427.......69......2 or 4 bolt
3963512....454.......70-76...2 or 4 bolt
3969852....366T......68-84...4-bolt
3969854....396.......69......2 or 4 bolt
3969854....402.......70-72...2 or 4 bolt
3969858....427T......68-84...4-bolt
3999289....454.......71-79...2 or 4 bolt, some "CE" replacement blocks had four bolt main caps
3999290....396.......68-69...2 or 4 bolt, Truck
3999290....402.......70-72...2 or 4 bolt, Truck
3999290....402.......72......2 or 4 bolt, Passenger
3999293....366T......68-90...4-bolt
3999294....427T......68-84...4-bolt
100511

[F&J]

The bad thing about printed words is that you can't hear the tone of voice or sarcasm, if it was there. Don't loose sleep over it.

You claimed not to want to rebore the other 7. That's why I suggested a sleeve. Some machinists like to keep the overbores to a minimum, so if they have one deeply pitted or damaged bore, they sleeve it. Some owners would prefer to have no sleeves and bore them all and get new pistons.

I would not run a motor with one mismatched weight piston, especially in a performance motor. (such as one 40, or a replacement 30 that's not a match) So, If you don't bore the other 7, you still need to find a correct match for the one that gets sleeved.

[F&J]

Small blocks from 1970 and newer use a 3 letter suffix on the front stamped pad. 69 and older are 2 letters. Big blocks may be the same? I'd look to see what is stamped on yours. I am thinking it is a 70-up 402? The codes will tell what you have.

[68NovaSS]

It's true you can't hear the tone or way a post was meant. Nothing I see shows any contempt or disrespect. Relax, we're all good guys and here to help.

[Deuce]

Just go ahead and buy a set of 60 over pistons and be done with it. With 7 30 overs and one weird 40 over ... the balance will not be right. The cost of 7 individual 40 over pistons will most likely exceed the cost of a set of 60 overs.

The 40 over cylinder bore is most likely worn and NOT a good round hole. I would have the block squared ( deck wise ) and then with a set of torque head plates installed ... bore it 60 over to have eight good round cylinder bores. Have the assembly balanced ...

[Chevrolet4x4s]

I think it was 69' that they refered to them as 400s then in 70' iirc the 400 small block came out.
Shane

[Double_v23]

http://up.craigslist.org/pts/558136898.html

According to this guy "yes they made them" he is obviously a chevrolet afficienado.

I contacted him about wanting to buy the 396 he is advertising as a 400 with 402 pistons. I never got a reply....weird.