Rattle sound from passenger side valvetrain..

fishy68 said

Blown header gasket??? Sounds real loud on the pass side compared to the drivers side.

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You be surprised how it sounds like a knock

Try tightening the header bolts, if the sound changes pitch its NOT the valve train but the header gasket leaking

I placed a wet towel on the header flange to see if the noise changes tone, if so bad gasket or leaky headers