Worn valve guides don't cause a knock. You might hear a really light ticking sound but you'd need better hraring than I have to hear it.

Valve train noise isn't a knock. The valve train taps...like a drumstick on a light surface. A knock is a heavy metallic thump. A rod knock is lighter than a main knock. If you have a 'heavy' noise that seems to increase at the same rate at the engine rpm increase, you don't have a valve train noise. If the noise is lighter and seems to increase at twice the speed of the rate of engine rpm increase, you have a valvetrain noise. Don't take the heads off just yet...you haven't diagnosed the problem.

You said you have a big cam...and that you're running the stock valve train components. Please let us know the cam specs..that should help. If you want to tear something apart, pull the valve covers and look closely at the rockers, the studs and the pushrods. If the cam has a giant lift to it you may have bent or damaged any of those stock components. If you find something bent replace everything...it indicates a bigger issue. If you don't you'll need to look further. You don't even need to replace the valve cover gasket to do this job...they're reusable if you don't tear them....
Good luck!

 

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