[Jay S]

Originally Posted by Stuckinda60s

I know this is an old thread and not to beat a dead horse, but it might be worth a mention. I saw 2 Blocks that had splits started at the dowel hole, traveled through the block and terminated at the opposite dowel . They both had split pins instead of dowels. At the time I thought that the pins were the cause of the fracture because they weren't an interference fit and only had the spring of the pin for stability, which could be diminished by vibration and allow movement within the hole. They were the 557 block.

Good info. I think the main caps for various reasons (alignment, power level ect) leverage the those non blind holes for the pins and can cause the block to crack at the dowel hole. To prevent cracking in the block at the main cap dowels it does not appear to really make a lot of difference if the 500557 block engine has dowels or roll pins, both can start a crack at the dowel hole. I think the roll pin is a little better and can handle more misalignment, but some think the dowel is better. I don’t think either is a much better than the other option. If there is some misalignment in the dowels when the main caps are tightened down even a stock 2bbl engine can fail at those dowel/roll pin holes.

I think a simple solution for keeping mildly built engines with 557 blocks together is double checking pin alignment, and using ARP main studs to increase the clamping force on the main caps. That seems to limit the stress that is sent thru those dowels or roll pins that are indexing the caps.

I have been running a main girdles on higher HP 557 base strokers for awhile now. The engines have been through some inspections. I have seen some fretting on the pan rail supports, but have not seen any negative effect on the mains themselves. One was at the track and some head porting let antifreeze get in the oil, destroying the bearings and bent the crank. It happened at MPH cones. The block took the abuse fine, but that was a bit more of a test than I was looking for. LOL