2 bolt mains are fine. The number of bolts is NOT the problem, it's the webs that are weak. When was the last time you saw a main cap come off from bolt failure? There are guys with blocks that are stock 2 bolt blocks(Fords, Chevy etc) making tons of power without issues.

The aftermarket blocks that go for 4 bolts, do so to distribute load more evenly throughout the main webbing, to prevent the block from cracking. Those blocks are also able to handle a substantial amount of power, far more than most people could ever afford to build.

Aluminum blocks are a different matter, since aluminum is weaker they have to have multiple bolts to distribute the load and prevent everything from squirming around.

 

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i was referring to the style of block (stock vs BOSS or DART, etc...) not just the fact that theyre 2 bolt.

351C's are (mostly) 2 bolt, as well as a lot of 460's and (like you stated) make TONS of power.

so yes, the metal composition is the issue, not the number of bolts.