So more confusion to add to the timing advice / debate....
I have total set to 36*. My distributor has a mechanical advance of 30*, so this means my base is 6*. The vacuum can that came with the distributor adds 25*, so at idle I am at 31*.
If I were to add a vacuum can with just 10*, then my idle timing would be 16* which is way to low.
I have been told by someone far more experienced than me that my current setup has a base timing too low and that I should be more like 16* + 10* vacuum canister which would yield 26* at idle with vacuum and that I should get a distributor with 20* mechanical advance. Frankly I don't understand how the two setups would be materially different as my setup will have a more aggressive mechanical ramp that should offset the lower base timing.
What I am wondering is if it would be worth it to make all of these changes to the distributor ? Maybe I am running too much timing (e.g. on deceleration / engine braking) thus causing the backfire? But under WOT, the car feels great.
1965 GTO Convertible 3 speed tri-power drum brakes originally
400 cu in with tri-power
4 speed Muncie