I got a spare BBC tall deck block and just found it is cracked from 2" down the top of cylinder 4" -5" long .

This block can be saved with a sleeve or is good heavy piece of junk ?

If it were me, I would rob the 4-bolt caps and junk it. Tall decks are not that hard to find.

nothing wrong with a sleeve in my book

There is nothing wrong with a sleeve, but Is the block worth the cost of sleeving it? I am not a big block guy and I don't know how hard a new block would be to find. My understanding is that the tall blocks are not hard to come by. Weigh out the cost differences. Witha crack that size I would probably look for a new block.

It depends on where the crack is too -- if its in a spot that will spread into the main web or an oil galley then junk it. I'd have your machine shop look at it and go with their recommendation.

It's much easier to tell by looking at something like that than guessing over the net. Plus, if you have someone look at it that actually installs sleeves then you'll probably get a good recommendation.

Who informed you of the crack? Can you take it to a reputable shop and have it sleeved?

Why are you being drawn to the "Dark Side" in the first place young LUKE? (Big Blocks)