converting back to stock rockers will be a little tough to do. to fit the crane shaft mount rockers, you have to mill the heads .170" where the rocker stands are. then drill the holes and tap to 3/8-16 thread.

 

OK so that won't work. I was just thinking that maybe your valve train components were too heavy and causing bad vibrations/harmonics with the heavy springs. Try a different brand of spring maybe?

 

well, i don't see what i have as being a problem. here's where vinci used the 1.7 shaft with the 833 springs and took the motor to 7000 rpms with no issues. i'm even using 3/8" pushrods. granted i'm using 1.8 rockers. so, something is amiss. for now, i'll just continue to shift at 6200 rpms. i'll work on getting the newest design AFR heads that tony and i talked about next year.

http://www.vincihiperformance.com/C6...T%20GRAPH.HTML

 

You can't compare that to yours. Different rocker ratio means that for a given engine rpm and cam lift the the valve end of the rockers and valves are moving faster. And the heavier pushrods could be the blame.