400 Small Block swap

[rpounds]

I am considering a swap in my '75 from a 350 to a 400 small block. I have an opportunity to pick up a 400 on the cheap (free), that I can take my time building up and stabbing at a later date.

Question . . . are the motor mounts in the same location for a 350 and a 400? Everything else should line up fine, but I have been told the mounts are different.

Any help would be appreciated.

Ron

 

[Jack]

Chevy 400 small block mount bosses on block are in same position as Chevy 350 bosses ... simply use the same configuration motor mounts as in vette now. If it's a Pontiac 400 I wouldn't expect the same. Get the sbc 400, take your time, then enjoy! BTW, a 2-bolt main 400 (once fitted with aftermarket 4-bolt main caps) is stronger than a factory 4-bolt main 400. G'luck!
JACK:gap

 

[rpounds]

Thank you. You have confirmed my thoughts.

I have heard that the 400 2 bolt main with studs and converted to 4 bolt with splayed caps are the way to go.

Thanks for the info.

Ron

 

[Dave L.]

You will also need a 400 harmonic balancer and flywheel as the small block 400's are externally balanced.

 

[rpounds]

Burglar,

Thanks. That much I was aware of. Also, the 400 has the center two cylinders on each bank 'siamesed' which means that I have to use heads that have been drilled for steam holes.

Here's a question about the Harmonic Balancer . . . '75 Vettes use a small diameter damper in order to clear the front frame cross member. Do you know what the stock diameter damper is on a 400 small block and will it clear the cross member?

Thanks again,

Ron

 

[Dave L.]

GM part# 6272225. 8 inch. don't know the answer to your clearance question.

Dave

 

[JohnZ]

You shouldn't have a clearance problem - Vettes back to '63 used the 8" balancer on SHP small-block engines, and all frames from '65 up have clearance at the front crossmember for the big-block balancer, which is located further forward than the small-block balancer.

 

[rpounds]

Thanks guys. This is all very good information. I live in Southern California and the engine is in Oregon. It belongs to the father of a friend of mine. I can have it for nothing more than the shipping costs. I have a few mixed feelings I guess about the swap, but the engine that's in the car is not original anyway. So I figure I can pick up some low end by rebuilding the 400 and sticking it in there in place of the current 350.

Thanks again for this information . . . now I have to go make that phone call . . .

Ron