[voodoosurfer]

Ok I accidentally posted in the welcome forum, sorry. I was asking about my fathers pontiac 400 engine. if it was a small or big block? someone posted that all pontiac engines are medium blocks. is this true clear thru the 350-428's? I am only familiar with ford engines so this is new to me. thanks to the previous reply and all future replies.
Shane

[Lonestar]

Pontiac did not make small or big blocks in the sense of what Chevy did. They are all dimensionally the same with minor exceptions...hence what some people refer to as a medium block.

[GSXMEN]

Biggest difference between the 400" and the 428/455 is the main bearing diameter. The aftermarket has cranks available in the 400" main size, to give you many more cubes!! I believe you can go out to a 455" with the 400" block, going that route.

[voodoosurfer]

HHMM! well thanks I have been into cars for the last 17 years and never knew that pontiac motors and chevy motors were different. I feel dumb even having to ask this but isnt pontiac a gm product same as chevy?

[68c10owner]

yes they are both gm as are buick olds and caddy. all of them have/had their own motor design. i can`t remember when but somewhere in the mid 80`s i think, the ponitacs started using small block chevys and i think the other gm cars did to. i`m a chevy guy and never paid much attention to the others so i`m not a big help to you but i do know that the pontiac motors from the 287 to the 455 are the same on the outside.

[Claymore12]

I believe '79 was the last year of the Pontiac blocks in production as far as GM is concerned- there are after market blocks available now that can provide for taller decks and more cubes. After 79 though pontiacs switched over to the GM corporate motor.
And yes there are a fair number of places that will sell a stroker kit to turn that 400 into a 455.