which is the most solid B20 block to use for a vtec head combo?

 

you have the option of either b20b or b20z, b20z is a little higher compression, in turn being better for all motor applications.

 

Unless you're getting a really good deal on the B20 you can probably get and LS block and sleeve it, bore it out to 84 or 85 for the same price if not a bit more

B20-$800-900
B18 $50-150
Sleeves 600-800

A sleeved block is better and you won't have the crank case pressure problems that the B20 is nototious for.

If you got with the B20....like mentioned earlier, the B20Z will give you more compression...but the stock pistons in both suck! You'll have to cut reliefs in them if you run an aggressive cam. I'd get a B18, sleeve it, bore, pistons, etc for 1500ish and call it a day