Just a thought.....

[Darkelf]

Since the 3a and 4a blocks are pretty much the same thing, it should be possible to bore out my 3a to 4a specs right? Theoretically speaking....

[Petros]

There was a service bulletin about overboring the 3a block .040, there is a history of occasionally cutting into the water jacket and getting combustion pressures in the cooling system. The fix is to sleeve the engine. I did not have this issue when I over bored mine this much, the 4a is even larger. So I would not do it. Get 4a block.