<VV> Odd sound - update

[Bob Gilbert 1]

Hi,

A few day ago I requested some help with a sound like a lifter noise but
with a sharper, "metallic" rap in my recently built (<500 miles) 3.1

Several people suggested a problem internal to the engine so I removed "the
top" of the engine, carbs on down to and including the turkey roaster.

Nothing is loose and there are no visible marks and no signs of part A
hitting part B and no sign of any foreign material.

I can turn the engine over easily by hand and there is no indication of
anything touching or obstructing anything.

And of course, with no plugs I can also spin it over quite fast with the
starter and still no unusual sound or vibration!

If it was a valve seat issue you'd think I be able to hear it.

I am stumped and the only thing I can think of is a lifter problem that
doesn't show up under these circumstances.

Is that possible?

 

Any other ideas or suggestions most welcome!

 

Meanwhile I have ordered a borescope to take a look inside the cylinders but
it will take a week to arrive.

 

Thanks in advance,

Bob Gilbert