[Keithc8]

We will normally use the early blocks like 69 thru 74 castings. I have had some blocks that were made in the late 80's and they looked pretty good as well. A lot of this durability deals has to do with the stroke weight of the rotating assembly as well as RPM. I feel all of the blocks are good for 550 to 575 HP. Where we have seen some of the problems is with the stroker stuff the guys are turning 7000 to 7500 with the external balancing. This whips the crank and will knock out the number 2 and 4 main. I have seen it crack the blocks in the main bolts holes as well as crack the block in the main webbing. I feel that if the engines were zero balanced or externally balanced this would not be as a big of problem.
Eagle had just released their 4.00 4340 steel crank in a zero balance form where it does not take 6 to 8 pieces of mallory metal to balance. Now we can run these engines zero balanced like the Chevys came from the factory. This makes everything much nicer, just get a zero balancer damper and flywheel. Good luck, Keith Craft