im keeping my eyes peeled for 400 blocks at the scrap yard and just to double check my knowledge, a 400 has 3 freeze plugs on each side of the block whereas a 350 only has 2, correct? Also the heads on a 400 have steamholes? Any other quick checks to tell the difference? Thanx.

 

400's started with 3 freeze plugs per side, later went to two.

Both the block & heads have steam holes. It's the block that needs 'em.

Externally balanced (if the damper and/or flexplate/flywheel is still on). Casting #'s. 4.125" or larger bore.

 

Most 400 blocks only have 2 freeze plugs.

They will all have the steam holes.

They also have "unbalanced" harmonic balancers and flex plates.

Easiest way to identify them with certainty is of course the casting number. 509 casting is the most common but there's one other that doesn't come to the top of my head at the moment, check www.mortec.com .

If a motor has been stripped down but still has the heads on it, sometimes a less sharp boneyard employee will let one go as a 350. Don't bet on it though.

 

the yard people are no problem, its a set price for any long or short block pre 92, be it an ironduke or a 454.

and that website is great, ill use casting numbers then, thanx.

 

Wow. Now there's political correctness for you. It would have been almost as easy to say "a guy named 'Norm', but spelled backwards and with an extra 'O' in there..."

 

bwahahaha.



anyhoo, the way i check when im walking down the truck isle in the yards is i look at the backside of the balancer and glance at the freeze plugs if im lazy.

3 freeze plugs are a dead giveaway, but like was said, they did come with 2...

with the balancer, you're looking for a "buldge" or some other counter weight looking thing...

 

the 400 blocks that only have 2 freeze plugs have the boss in the side for the third freeze plug...it looks like one should be there isn't the balancer doesn't have a "buldge" , it has a machined place on the balancer, a quite large machined place...if your look at the balancer...it's hard to miss

 

Not all have the extra boss....

Here's my 73 509 block.

 

Incidentally, in that pic, you can see the "missing" chunk of the harmonic balancer, to "unbalance" it.