Kirby’s intermediate lifter pushrods set up, interesting. Here is the challenge, at least as I see it. Those heads can’t breath much past 4800 rpm and maybe not even that deep, even with big valves and some porting. The cam I have in one of my 261 motors is 280 degrees and .492 lift. Its an aggressive street cam. I use smith brothers 3/8 moly push rods and their matching ball adjusters and did not enlarge the holes any and four years and last night, no indication of any clearance issues. have a Clifford cam 290 and .512 that I ran years ago before I knew that bigger is not better. Ran that with the smaller TRW replacement push rods and no issues but I would suspect that the higher lift might be close. That being said, the head can’t use the lift. So while it may be possible, the design of the ports is the limiting factor, at least in my opinion.
Last edited by Dragsix; 07/14/2018 9:25 PM.
