I'm looking at going with the AFR 205 heads for my 351W stroker motor (408). As I understand it, the AFRs come with 2.08 valves which may require flycutting the piston valve reliefs. Is this true? And if so, does it throw off the balance of the assembly? TIA.
It depends on what kind of pistons your running and your cam, but usually once you go to 2" valve you need to have the pistons notched. have you already purchased the rotating assembly for your motor? Many of the stroker kits come with the valves cut already, but some don't.
long story, but *both* of my engine builders of a 331 and a 408 used Dart Pro1 heads. The 408 made about 540hp with solid roller and a Super Victor intake. Not sure exactly which Pro1 head they used yet.
Just contact the company that you will be purchasing from and ask them. If they don't know get the piston part number and call the piston company. Most pistons that clear a 2.02 valve should clear a 2.08 but it's best to ask.