are 400 blocks pretty cheap and common? can you fit 350 parts on the 400 block? is the 400 a small block or big block.

 

Usable 400 small blocks aren't all that common, but they're out there. Because of their desirability, be prepared to pay more than you would for a garden variety 350. Parts are as interchangeable as with any other small block, but the heads will need steam holes drilled if they don't already have them.

 

yep things will bolt up as they will any 350. Like Apeiron said, the heads will need steam holes. That isn't too hard. And, of course, if you didn't already know, you will need new pistons and a crank (unles you run bearing spacers or something).

I could get a fully prepped 400 for i beleive $400 from my local shop.

 

400's are small blocks but the 402 badges you see on some muscle cars indicate that it is a big block...basically a 396.

Most parts interchange.... if your talking a two piece main 350 and a 400. A 400 crankshaft will not interchange with a 350. The mains are larger than a 350's. They can be turned down to fit in a 350 block...now you have a 383. A 350 crank will fit a 400 block with main bearing spacers or special main bearings...now you have a 377. 400 rods (5.65" long measured from center to center) will not change with a 350's (5.7" length) without custom pistons. 350 rods in a 400 is a very popular swap and there are several manufacturers that make pistons. Camshafts will interchange between the two but will "act" differently because of the larger displacement of the 400. A radical cam in a 350 will be tamer in a 400.

Because of the larger displacement of the 400, compression will be raised on a 400 as compared with a 350 in regards to cylinder heads...and of course...the steam holes needed for the 400.

400's are externally balanced and have specially balanced flywheels/flexplates and harmonic balancers. They will not exchange with a 350's internally balanced assembly.

Everything else I can think of is a direct swap.

 

And if anyone ever offers to sell you a 400 block and throw in a set of stock 400 heads for free, get them to take $50 off the price, which is about what the irritation of getting rid of those things is worth.

 

how big can you bore and stroke a 400 block. 430, 435, etc. ??? Is there any downside to the 400 blocks? How much would a basic plain block cost?

 

There are all sorts of problems with factory 400's. Cracked main webs, cracked cylinder walls, cracked coolant walls, etc. Susceptibility varied with year of manufacture.

How much dough ya got? A Motown block fixes all of the factory weaknesses, allows the boring and stroking you desire. More expensive up front, but doing it right once is typically cheaper than doing it cheap first and right second.

 

i got lucky. one of my friends sold me his truck with a 400 and a th350 in it for $500. been running both in my car for 3 yrs now

go for a 2 bolt 400 instead of the 4 bolt. the 2's are actually stronger than the 4's due to the way the additional bolts were drilled. sbc 400 specific parts are cheap enough and easily found (my crank was in stock at the local parts store).

unfortunately still stuck with the 882's. got little/no money to upgrade, but still got tons more power than my tired old 305 had.