Are there different stages ... 1,2,3 ... ?
Do you have one that will work with an otherwise stock 6.4L? Doesn't need special valve springs, machining or valve reliefs in the pistons?
Anything over a stock cam I highly recommend springs and pushrods. Even with a factory cam it's the high backpressure and boost that makes the valves unseat. Some people run stock pushrods, but I can guarantee you that they are deflecting and losing lift.
Anything less than a stage one you may as well stick with a stock cam.
If you are pulling your heads I would do upgraded springs regardless of upgrading cams or not. My springs do not require machining the heads to fit.
If you upgrade to heavier springs then you need the heavier pushrods to go along with them. Otherwise they are bending under the stress and losing lift.
The stage one is meant to work without valve reliefs. But if you have pistons out it is recommended to cut reliefs in for safety. In case you break something and over rev the engine. But that can happen, even stock engines hit valves to pistons if over revved. Seen it on a guys stock 6.4 truck who was towing in tow haul going down a hill. He over revved it till they hit bent pushrods and rockers.
I do offer a full stage one kit if anyone is interested
It consists of:
heavy springs, upgraded pushrods, and a stage one reground cam. Kit price is $1200. Normal price is $1323 to buy pieces individually.
Stage on kit with Colt billet is $1475 kit, $1623 individually.
Stage one regrind kit with new oem lifters is $1575 normally $1822 buying individually.
Stage one Colt billet kit with new oem lifters is 1850, normally $2122 individually.
Hope all that helps. Let me know if you guys need anything.
Thanks, Morgan