old motorhead

iTrader: (10)

I'm going to look at an old truck that supposedly has a 400cid small block chevy under the hood. If I remember right, you could identify the 400 block because it had an extra freeze plug on each side. Seems like a smaller small block had 2 freeze plugs vs 3 on the 400. Or was it 3 vs 4? Help appreciated. I'll probably buy it anyway, but I'd like to know what I'm looking at.

YenkoST

iTrader: (11)

The freeze plugs are the same number but a good way to tell is that on a 400, the freeze plugs are offset....one is toward the bottom on the block instead of in the middle.

kbracing96

iTrader: (26)

Another way to id a 400, is that its externally balanced, and the harmonic balance will have a big chunk missing out of it and there will be a counterwieght on the flex plate.

old motorhead

iTrader: (10)

I do remember the externally balanced bit. All other small blocks are internally balanced. Didn't know it was that easy to spot on the balancer. Thanks.

mred

iTrader: (5)

easiest way isthe block around the freeze plugs stick out the have i guess you call a hump around the block 2 humps usually meant 2 bolt 3 meant 4 bolt
but not always
casting number
330817..... 400...72-80...2


3951509....400...70-71...4
3951509....400...74-80...2
hope this helps
Ed

BADMOFO

330817 73-76 Passenger, 75-80 Trucks 2 bolt main + 3 freeze plugs
3951509 73-76 Passenger, 75-80 Trucks 2 bolt main + 2 freeze plugs
3951511 330817 73-76 Passenger, 75-80 Trucks 4 bolt main + 3 freeze
plugs

old motorhead

iTrader: (10)

Where is the casting # located? Thanks.

EXTREME

the dipstick is on the drivers side, correct me if i'm wrong.

mred

iTrader: (5)

so is a 350

YenkoST

iTrader: (11)

Unless is an ext. balanced 383. You will see the last 3 digits on the block.