Irregular knock from engine

[nigel911]

Pulling in to the drive yesterday waiting for garage door to open when I notice a faint 'knock' from the engine.

Pull car in, open engine bay and listen. Nothing abnormal for a minute or two, then a slight 'knock' which appears to emanate from the 'bottom' of the engine - definitely not from the chain housings (not running oil fed tensioners). The noise is not loud and is very irregular - any ideas? Cheap ideas always preferred over expensive one's...

[nigel911]

Of no relevance but the car had just been filled with gas and had driven through a large Florida downpour on the way home.

[Steve W]

Perhaps crossfire from wet old ignition wires?

[nigel911]

New leads 3 months ago.

Any more before I take it to the spanner?

[RoninLB]

Originally posted by nigel911
The noise is not loud and is very irregular - ..

a piston pin knock can be easily diagnoised..........Ron