in my opinion total timing is dictated by cylinder pressure/chamber design/ quality of fuel. just because one guy does something doesn't mean you should. don't think that a total advance number is some blanket rule. the higher the cylinder pressure the less tolerant the engine is of it with a given fuel, and the more eficient the engine is the less timing it needs. i'm pretty sure the summit cam closes the intake valve around 61 degrees ABDC. that's fairly early when you consider that a stock magnum closes the intake valve at 67 ABDC, and that dosen't include all the closing ramp. i've found that some carbs in these stock engines are less tolerant to aggressive timing than others. i have a stock 440 that i've alternated between the factory 4618avs and a 1407 edelbrock. my initial thoughts were that these carbs are so close in size and function that ignition timing changes weren't necessary; wrong! i've had to learn thru the years that the vagueness the phrase "it depends" is relevant.