Problem Valve Spring!

Bewy said

What post #4 said. 'Clearancing' a rocker arm....is weakening it.

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The stamped steel rocker for a 340 were clearanced from the factory. All of them were. The T&D rockers pictures above were clearance and used with a 686 lift roller cam and never any issues. We used what we had . The new engine we went to beehive springs and 1.6 rockers

He is using stamped steel rockers with a small hydraulic cam clearancing them will be just fine. Or find factory 340's that are clearanced. Budget builds you use what you have available. I may have extra 340 rockers if needed