[FFRDave]

I thought it was chain-slap too, and I have been told such in the past. A new chainguide and sliders and a lot of checking the chains' range of motion has pretty much taken the chain-slap theory and tossed it out the window.

You are absolutely right, it just seems to happen at times. For me, it is mostly at high RPM while hauling a$$ across a big sand dune. It just sounds like a rattle in the motor.

I have been able to reduce this noise by putting enough of a bend in the actuater arm to apply a little bit of pre-load, so that at WOT the flapper is pushed more firmly against the stop. It seems like there was enough slop in the powervalve that it could kind of flap (or vibrate) like a reed on a saxiphone. I never thought about side to side motion though.