i was thinking about putting a 406 in my 1990 but dont know if it will fit or not. i know with alot of cash i could do it easly, but guess what i dont have alot so i was wondering if its possible and if there are any big problems that i will run into if i tackle this job?
thanx

 

The 400 is a small block like the rest and will fit with no problems. You will need to get the right motor mounts. The flywheel and starter will have to be for a 400 i believe. But clearance wont be a problem.

 

Starter will be the same...all SBC engine mounts are the same...exhaust is the same...just need a 400 flywheel.

 

400s do not have parallel bolt holes to mount mini starters. When you have the block machined get it drilled for a mini starter (some minis have offset bolt holes now).

You also need a harmonic balancer that is externally balanced. And there are the issues of connecting rods.

The motors are externally the same.. but some special circumstances exist that must be considered

 

If the 406 is a BB it is going to be tight. One of my buddies put a 396 in his '87 no emmissions,heater or A/C and it was still pretty tight.

 

ok the block im might be buying has everything on it and came out of a stock car, has nyone done this swap, cause i thought that a 400 block was just a little bigger than a 350?
anyways thanx for the replys

 

no, a 400 block is externally the same size as any other small blcok chevy. As was already said, the only issues are the flywheel which will probably need to be "unbalanced"; the fact that all 400 blocks have only the driver's side oil dipstick in the deck surface of the block which will not work with late model exhaust manifolds; they pre-date the invention of the 12-3/4" flywheel, and so are missing a starter bolt hole required for that; and the balancers that are available have the 1:30 timing mark instead of the 12:00 one that these cars' accessory setup requires. none of these are insurmountable. I drove my 83 around for about 11 or 12 years with a 400 in it, and it will be going back in soon.