My 340 has 4 bolt mains, stock 70 340. I make moderate power with it around 1200RWHP and the jury is still out. Here are some thoughts:
1. The splayed bolts go through the main and into the water jacket. The potential for leaks is high.
2. There doesn't appear to be enough meat in the main cap to be effective (we will see)
3. 2 Bolt mains do have their limitations and most would say that its important to hold the cap in place, I think a better quality crank is money better spent.
4. An aftermarket cap is money well spent along with good studs, again if the block pinches the crank its all done and goes kaboom.
5. True if you make big power an aftermarket block is cheap insurance, I mean most short blocks cost 3-5 grand in parts and heads vary but to make big power you have a lot of money in those heads. So why throw away 8-10 grand when it does go boom when you could've spent 4k more in an aftermarket block. Oh and by big power I mean 750 plus.
