JCB 3C with loud rapping noise

[mgallo]

HI folks,

I have a JCB 3ciii with a Leyland 4/98 NT. The other day upon starting I heard a loud rapping noise. I couldn't trace to engine (or maybe torque converter)?

I have pulled valve cover, everything appears normal.

I have pulled the oil pan, and found a few small brass pieces and two small pins.

I took the rocker arm off and turned over the engine by hand and still makes the noise (so probably not a valve)?

It seems to be only during a certain spot on the rotation, I thought it was cylinder 4.

Took the rod cap off, turned the rod and hand turned the motor and I think(?) the noise went away, but not sure.

So my questions are the following.

Is there brass and small pins somewhere in the engine? The oil pan had been off sometime in the past since there was no gasket, only blue silicone.

What does a failing torque converter sound like?

I am in the Niagara Falls, NY area.

thanks,