Engine Size Question
 

I'm a little confused as to what the correct size engine is in my truck. It's the original big block and the fenders say 400, but the SPID says 396? I've also heard 402. Which is correct? Thanks

Re: Engine Size Question
 

What year and model is your truck?

Re: Engine Size Question
 

In 1970 they went to the 402. So if its a 68-69 its a 396 or 70-72 is a 402. Sometimes the guys making spids just typed whatever the RPO code was for. If it has 400 badges I'm assuming its a 70-72

Re: Engine Size Question
 

You need to Google to find the history of this, it's too complicated for a quick answer.

Basically the BB Chevy as we know it was introduced as a 396. Used in a truck application, they rounded off to 400. Also the 402 was a 396 with an .030 overbore. That is what was used in 70-72. There are a lot of rumors as to why:
-bunch of pistons made wrong and could not be rejected
-bunch of bad blocks that required an overbore to use
-couldn't have a 400SB that was bigger than a BB
-etc.

Re: Engine Size Question
 

My 2cents worth. I was under the impression '70 and later 400cid was of small block configuration509/511 blocks 2bolt and 4 bolt,hence most are in dirt stock cars. the 396 was 396 (unless you do the math bore x stroke=402).The 396 was for insurance/road racing certification.Then GM went to the 454. cars and c40,50,60 got the 427(truck tall block 366/427,cars 427/454). Please someone that actually has facts step in.

Re: Engine Size Question
 

The 402 replaced the 396 in all gm vehicles in 1970. Some reason cause gm to bore all of the 396 out. Even a Ss396 in 71-72 chevelles, etc have a 402, but the SS396 stuck because of its reputation as a potent package. There have been other threads on this board discussing this.

Re: Engine Size Question
 

And for some unknown reason, on the pickups they used a fender badge that said 8-400 when it was in fact a 402. Why? I do not know.

Re: Engine Size Question
 

It's a 71 C20. The fenders say 400 and so does the build sheet, but the SPID says 396. The option code on both the build sheet and SPID are the same, L47 I think, but I don't have it in front of me at the moment.