[TR] Dieseling and pinging

[Wayne]

I just got the TR6 on the road after an engine rebuild.
The head was shaved to raise the compression and I know this may cause
pinging.
Engine was started with high octane fuel and ran fine, but after a few days, I
filled up with
regular fuel and I am getting pinging when accelerating.
My question is do I have to run high octane fuel or fuel additives or can I
adjust the ZS carbs?
The engine also keeps running after I turn it off, I think this is called
dieseling.
What causes this? Will carb air/fuel adjustment fix it?
I also tried to check the timing with a timing light, but what I found didn'y
make sense to me.
I set the static timing before the initial start-up @ 12 BTDC and the engine
started right up :).
After driving the car, I thought the acceleration was underpowered, so I tried
timing the engine
with a timing light, with engine @ idle 800 RPM, and the vacuum advance still
attached,
I was no where near 4 ATDC. And when I tried to rotate the distributor to
advance the timing
to 4 ATDC, the engine would run rough. I ended up rotating the distributor the
opposite way
and ended up at around 10 BTDC.???? I went by sound not by what the light
showed me.
Does this make sence? I also removed the vacuum tube from the advance on the
distributor
and it did not make any difference to the idle? Should I be concerned that my
vacuum advance is not
working?

Any info on this will be apprieciated.

Wayne
73 TR6