426 stroker, is it reliable?

It seems that stock blocks suffer from flex and bust the cylinders at high hp levels. There are guys running them at 600+ hp with no issues and some have busted cylinders at less than 600. It all depends on the block and how sharp the tune is I suppose.

My 408 was in the 570-580 hp range and the main and cam bearings showed signs of block flex when I tore it down for a refresh and cam upgrade. When I found this I started looking for a R block and eventually found a complete but apart R1, Indy headed 394. These blocks are heavy but very strong.

BTW my 434 is not for the guy who just wants to stroke his engine for some extra power. I had no illusions when I built it what I was getting. That being said it get's driven a bunch and so far raced a little. It all depends on what you are willing to put up with.