Bob Spidell,
Thanks for your response. I have done a few things based on your notes:
1) I found a few slight kinks in the steel fuel lines between the tank and fuel pump, so I cut out that section and used flex hose to the fuel pump (just another 3 inches from what was already there). unfortunately, that did not help.
2) I had a backup Facet Fuel Pump that I have been carrying with me, so I installed it on the passenger side of the car behind the footwell (consequently further away from the tail pip/muffler). I thought I had it fixed, but after then engine reached operating temp for a while (20 minutes-ish) while driving in 70degree weather - the facet pump starting clattering louder similar to the SU. I did use the rubber buffers when installing the facet and the default 'click' was well deadened at first.
3) Since I have a 4seater, I can easily check/trace the line all the way from pump to tank. I just can't see any points of leakage in the line. So i'm left with 2 more options - both of which you mentioned in your note on 5/1/2020.
a) Perhaps I have a leak in the fuel line that extends into the tank, and when the fuel level drops below that leaking point, the pump is sucking air (?). or perhaps at the joint itself at the tank. This is only a 5 year old tank, but perhaps it was delivered with these defects - I've had the problem as long as I can remember. OR
b) I need to do someheat isolation in the engine compartment, possibly with some creative use of DEI heat insulation for fuel lines and carbs.
For now, I'm going to experiment and see if the clatter starts when my fuel tank is at a certain level, rather than driven by heat. If negative on that - I may be pursing a new tank. thanks for the info.
Rob