[Walt Fricke]

Hmm

An acoustic phenomenon? I wonder if pulling spark plug wires one at a time would isolate this, or if the irregularity introduced by running on only five would mask it no matter which one was pulled.

If this is literally a beat frequency, you'd suppose it would be common on all stock 3.2s. Is the exhaust all stock?

Can the frequency be counted/timed? Now I am beginning to see why Rob sees some significance in the very small timing difference. However, isn't the frequency at an idle of 850 rpm roughly 4 Hz? Isn't that sub-audible? A beat frequency would be lower?

A small exhaust leak at a head gasket? When an air injector plug fell out of one of my motors with 2.7 heads I noticed it pretty much right away when idling in the grid. No such plugs in a 3.2, but - - -

Walt