Lot's of possibilities on this one. First thought is a valve briefly stuck and bent a push rod. With it running look at the push rod cover and see if you notice any movement of the rod bumping the cover.

Dave

Hello Paul Rozon,

So far while driving 'a loud very sharp clucking sound coming from somewhere in the engine'. When not driving with engine idling, 'erratic clucking sound'.

1. While not driving, does sound change when revving the engine- speedup get louder?

2. With engine running in the dark, look at ignition wires, spark plugs and cap for signs of spark to ground and hold hand at tailpipe for signs of misfire.

3. Do check for proper valve lash adjustment as David Dunton advises.

4. Touch everything external on engine for security. Anything that moves for rubbing/chaffing. eg. linkages, delaminating fan belt for slapping as it travels, loose fan blade, loose fitting oil cap, loose fitting air filter assembly making noises. Loose engine sheetmetal pans.

5. With engine running, use a mechanics stethoscope to listen top to bottom, front to back.

6. With engine running, use soap bubbles to look for blown head gasket, intake/exhaust gaskets.

7. Remember, with engine running in neutral, the clutch and part of the transmission are rotating, those also need listening to.

While doing all that, check the fluids and kick the tires. You should be closer to discovering the source of your clucking sound. Let us know. Good Luck. 

Thank you for the replies.  I looked at the engine today and found the problem.  Ran it a bit and then I noticed the sound seemed to be coming from the valve cover.  Stopped the engine and removed the valve cover.  Everything became obvious, the rocker at the very front of the engine was lying on the head.  The rocker shaft broke at the point where the bolt holds down the rocker shaft.  I tried moving the valve and it appears to go up and down ok.  So, now to replace the shaft.  I have a rocker arm and shaft assembly (used) that looks to be the exact size and shape as the ones on the car.  The rockers appear to be in better shape where they push down on the valve stem.

@1931-roadster 

Hi Paul

Even if the valve ends of the rocker arms look "better" than your originals, I would highly recommend having them reconditioned to get rid of any step or groove present..

It's a simple procedure and a good shop that does head and valve jobs will have the equipment to do the job and hopefully not charge too much.

That will give you a nice new surface and make it easier to get an accurate valve clearance adjustment. It will also result in the quietest valve train possible with no risk of the the valve end riding up on a step and resulting in a burned valve.

Just a suggestion of course.  🙂

Thanks for the information, it makes a lot of sense.