[greenwater]

I have a similar problem but altough with another engine maybe my recent discovery could put you on a track you have not checked yet. My engine is a chevy 383 stroker and would keep on running after shut of. Its a recent rebuild and carbon accumulation has to be put away as a possibility. The problem would occur only when the engine is fully hot. I have a remote timing mechanism and retarding it from its regular 10 degrees to as much as 3 or 4 degrees was not doing nothing. The idle speed then down to around 500 would not affect it positively neither. I had the ignition switch letting passing by some current as the instruments would stay on even at "off" position. I've solved that problem by installing an in-line switch on the instruments main positive wire but the expected curing of my run on did not solve then neither!

I am also running rich (edelbrock carb./electric pump combo) and modifying the jets/rods do not bring satisfactory...

Suspecting a too high pressure delivered to the carb. from the pump I tried to stopping the pump working a few seconds before switching off and IT WORKED the motor would stop immediately!

So I will install a pressure regulator on my fuel line and hopefully this will be the solution. Now the edelbrock needs to be ran at a 6 pounds maximum pressure and mostelikely the electric pump works at seven ...your set-up while different,holley carb. and mechanical (?) pump ,from my experience, could be suffering from a gaz problem also.The apparent incurable too rich situation in my case could very well also caused by a too high feeding pressure overwhelming the carb. but this I will be able to confirm only when my regulator will be on.

Coming back to my case it looks like the carb under overwhelming pressure was couldn't deliver the right mixture (too rich) and was not stopping dripping raw gaz at motor shutt of.....