Clicking Noise Heard Upon Throttle Stab

[KJL]

Hearing a little clicking noise when a mildly stab the throttle from idle. Got my stethoscope out but seem most noticeable if I removed the rod part and just listened in the general exhaust area. Couldn't pick up much when placing the rod against the IH's or head. I guues it could be an exhaust leak but it sounds to metallic for that. Engine runs fine. I did just complete some port work on the heads and it is possible a few small flecks of aluminum may have made it into the cylinder. Not that familiar with OHC engines and looking for some input regarding possible cause and additional diagnostic ideas.

I can also hear a little click when driving with the windows open at times.

Just dyno'd the engine to 7000 rpm and it achieved 400 rwhp. Clicking was there before testing however.

Thanks!