I have a stock 87 Silverado, My brother purchased me a motor and he says its a 400 but how can I be sure?
I would like to know which block it is to keep records and which intake to purchase(didnt come with one).
Also my truck is currently tbi, what all will I need to do to convert to carburated with out any problems?

 

Take the serial number off of the back of it and type it into google. You should be able to come up with something, or you could take it to a local machine shop and they can verify it.

 

While you can look at the freeze plugs to get an idea, don’t get hung up on trying to determine whether or not a particular block has three or only two, as the blocks were available in both configurations. If the block doesn’t have the heads installed, it will have at least a 4.125” bore, while a 350 or 327 would have had at least a 4.00” that may have been taken out to a 4.060” if it was over-bored a good amount, but it’s still a good way’s from the 4.125” minimum bore size of the 400. If the balancer is still installed, it will have a scalloped out area on the outer edge of it, but if someone used the 400 crank and balancer in a 350 block to build a 383 this is not a 100% identifier. Here is a decent site to look for the casting numbers: http://www.chevymania.com/

 

It has 3 freeze plugs
Block number is 330817
What do you mean a scalloped out area around the edge?

 

If the heads are off, the 400 has steam ports between the cyclinders.

 

Casting number 330817 is a small block 400.

Notice the cut out area.
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Best way to tell right there. Just look for small holes between the cylinders if the heads are off.

 

I know this for a fact..There could be 2 or 3 freeze plugs on the block, depending on what year it is.. All the 400 cranks had a small dowel pin in them, along with the bigger notched balancer.. 400's have a bulge in the block around the cylinder bores, you can feel them..
Also( found this)
330817 1970-80 400 150-180 2 bolt
3951509 1970-80 400 only 150-265 2/4 bolt

 

I'm guessing you didn't put that into Google as suggested. Google is your friend. Use it wisely.


http://www.nastyz28.com/sbchevy/sblock.php

 

like mentioned, you cant go by the amount of freeze plugs. best way is pull the head and look for the steam holes, if by chance they were filled, (my dad has his filled) the motor will be externally balanced