Triumph Repair: Loud noise from engine, weber carb, fan belt

Question
I have a 77 spitfire with a weber carb, and when i start the car it runs quietly for a few moments, then there is a loud grinding sound from the engine.  It doesn't seem to be effecting the engine, and I think it might be a failed water pump or viscous clutch, because the sound seems to be coming from that area.  Does this sound like a likely culprit, or could it be something entirely different?

Answer
If it's taking a few minutes to be apparent then the viscous clutch on the fan is a highly possible culprit.  There's normally a small amount of free play if you try to move the fan forwards/backwards but if it's more than a small amount it's time to either replace the clutch, or convert to either the earlier fixed fan or an electric fan setup on the radiator.

One way to check things would be to loosen the fan belt and see if the water pump spins freely or if there's a rough feeling to the bearing.

It could also be the alternator bearing(s) failing.

Cheers,

Jim