I don't remember any 340-specific stamped steel rockers, sounds like bunk to me.

Anyway, PLENTY of Mopar 318s have been built with camshafts similar to yours in terms of lift, using stock 318 rocker arms. Look at the bottom of your rockers to see if they are conttacting the spring or retainer. I bet they aren't. If no contact, rockers are not the problem.

You did say something that could have a bearing on the situation: Voodoo camshaft.

Comp Cams' HE line and Lunati's Voodoo cams have very aggressive ramps on the lobes. This puts higher stress on the valvetrain, which could cause more noise than a stock-type cam. The CompXE line is especially known for this, but the Voodoo is similar in design and that COULD be the increase in noise that you're getting.

I think you're worrying about nothing. If the lifter has 0.150 travel and you're using about half as preload, I don't see that reducing the preload would lessen noise appreciably. It may put the rocker in a wrong place on the valve tip, you can check for that.

If you want to buy shorter pushrods, first you find out how long yours are and then search out a shelf stock pushrod the right length, or have Smith Brothers or Manton custom build you some. Not impossibly expensive. Or send them a pushrod and say build one 0.025" shorter. But I think the lifters are more forgiving than that.

Have you checked the pushrod sides for contact marks with the intake ports?

R.