Will a factory set of 915 HP heads with their factory springs work with a .509 cam? thnx

no

not even a consideration

Only if you intend to turn that 509 cam into a 309 cam.

No chance.

Not unless you like what can happen as the results of coil bind.

those pistons are "used"

and abused - seriously they are out of a 360 using stock springs with 484 lift resulting in coil bind. The rotators had not been removed and a longer spring used either. After measuring the with a longer regular non rotator spring it would have been real touch and go anyway but the rotators were the straw that broke the camels back. It also cost a sleeve, head, cam, a couple of rods and a crank that could be salvaged surprisingly with a .010 cut.

What's a good set of springs to order for these heads? Their 915HP's, virgin, have been cleaned up, going on 440 six pack, 509MP cam, .030 trw domed,new Elgin factory length push rods, new Mopar factory style rockers, new CompCams rocker shafts, Rhodes lifters, and I believe they're the stock valves on the heads... my old heads seemed to have held up okay, 906's, but had a bent/stuck valve and had these on the shelf. thnx

I run Comp springs retainers amd keepers.Its a good idea to upgrade to them.The retainers usually arent a problem but why trust 40 year old keepers.Im running a .588 lift with my Comps solid cam.You will probally need new seals also.Rocky

"Thier 915HP's virgin" You will definately want to make sure they have the hardened seats in them or this new fuel "will" hammer them out eventually.

You have a PM

Stan