Clicking after engine shut off

[72 Invader]

I was running my 165hp I6 on the hose last night. After shutting the engine off, I heard 2-3 clicks. The clicks were 10-20 seconds after the engine was shut off. It sounds like a built-up charge was discharing, is this possible? And why would it happen multiple times?

The sound is also similar to the clinking of cooling metal, but I don't recall ever hearing this before now.

Any ideas of what may be causing this?



thanks.