Rocker arm trouble

Cummins9912v

Cummins9912v

New member
Hey guys I'm drawing a blank with rocker arm troubles on my p24, put a new motor in and used a 12v block, with 12v bottom end besides cam and pistons, bought a new Hamilton 207-220, ran the truck for 20 min and broke an intake rocker. No big deal? Changed the rocker and ran for another 10 min and broke a different rocker. So I had a new set laying in the shop. Changed them and it ran for 3 pulls before it broke another intake rocker. So my question is has anyone had this trouble and found a solution?
 
I took the rockers off and all of them move freely, head is getting proper oil, the valvetrain is stock besides 110lb valve springs.
 
In on this. A buddy had the same issues on his p24. First it pulled the threads out of the head. We put a thread insert in and then it broke the pedestal. Put a new rocker and pedestal in, pulled the thread insert out of the head. Repaired that again with a thread insert and no trouble since.

No galling, push rods straight as an arrow, beehive springs, never over 4k rpm. Stock cam.
 
Hamilton calls for .080 reliefs and I cut .200 because I want to go to a bigger cam later on, truck has absolutely no knocks, ticks, nothing. And has ran 3 5krpm passes before it broke another.
 
See if you can get a .010 feeler gauge in the spring at max lift in 3 coils for a min of .030 clearance at Max lift .. that cam has 360 lift you likely have coil bind . That's a big cam on a 4 valve need to know your springs installed height. Next break might be a dropped valve so I would check this
 
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