Engine differences (2v, 4v?)

[Mercury]

Hmmm a four bolt windsor block is a definite rarity. Might be that the block castings are from diffrent years, the heads in certian years did have diffrent valve and cumbustion chamber sizes but there was no diffrence in heads from a 4 barrel and 2 barrel setups.

Maybe the one block thats cheaper has had been bored already once before, or might have a sleeve in it. Ask them what the diffrences are, see if there Bull Shtin you. I've known for Mexican Windsor blocks to be refered as 4v blocks, but that was buy a rip off junkyard here in Fayetteville.

Now the Mexican blocks have thicker main bearing caps and a higher nickel content in there castings. Hope I was able to help out in some way.