[David Robinson]

Ya, he didn't really answer the question either. At the end of the video he says they used to set initial at max vacuum but it's not something you ever, ever want to do today. There are too many variables to set it that way performance wise but he never elaborated beyond that.

Based on what he's saying, it seems in my application, that setting initial to max vacuum would make sense since I can make the curve whatever I want and my initial timing at idle won't affect anything else in the curve.

 

[David Robinson]

I have a programable ignition (MSD)
I don’t remember exact details but here’s my thoughts. During cranking say 0 to 400 rpm I have Conservative advance, from 400 ish rising sharply to idle rpm I have my initial say 18 degrees.
From there it rises to full advance say 35 degrees around 2600,
I have no vacuum or mechanical advance as my timing is locked out at 35 degrees, programming curve is set by delaying the locked out timing to a max of 25 degrees.
so, cranking is 35 - 25 for advance of 10 degrees
Idle is 35 - 17 for 18 degrees advance.
2600 plus rpm is 35 -0 for full 35 degrees advance.

So, I'm pretty close to that. Initial at 16 degrees and 36 degrees all in at 2600rpm as well. I can accomplish the same programmable curve but I also use a MAP sensor and have a vacuum advance curve added in for 3D programming. You should be able to do the same if you have the 6530. My Duraspark is locked out at 46 degrees which gives me that extra 10 degrees for vacuum advance.

But with all that, I still don't understand how one determines the best initial. Why 18 degrees and not 14 or 20?

 

[David Robinson]

So I believe the answer is to have as much initial as the engine will tolerate at idle rpm without having an erratic vacuum reading and not pinging. It is better to have the most initial possible with less "mechanical" advance.

" To really make a trick street set-up you should only have about 10 degrees or so of mechanical advance in the distributor and about 24 - 26 degrees of initial timing on the crank to obtain your total of 34 - 36 degrees of total timing. This will launch you out of the hole much harder, and give you great jack rabbit starts from street light to street light. You NEED advance at low RPM to make that engine pull hard. It'll have MUCH better throttle response, a better idle vacuum signal, and it'll run cooler & cleaner. "

To those of you that know, would you agree with the above?

 

[David Robinson]

Yeah, and if you have a hard time cranking you can always put a momentary switch on the ignition circuit so you get her spinning first and then cut in the spark....

The beauty of the programmable MSD. I can program 16 degrees 0-300rpm and straight up to 26 degrees at 400rpm. No switch needed.

 

[David Robinson]

Most Windsors like to be in the 20s for idle timing. But if you are at something like 26 degrees mechanical, running ported vacuum, you are going to be pinging and overheating a lot when you're stuck in traffic at low speeds. I try to run as much mechanical timing as my engine will tolerate at WOT, at any speed. If the base (centrifugal, no vacuum) timing is correct for WOT, then the vac advance can be used to add timing to correct for high vacuum, when combustion is slower (like at cruise and idle).

So I have it programmed this morning 16 degrees advance from 0-300rpm and ramping up to 24 degrees at 700rpm and have steady MAP reading of 46-47pa(16inhg). AFR is reading 13.5-13.7

I haven't added in a vacuum advance curve yet but what would be a good starting curve to program in? I can have a maximum of 10 degrees advance. Using the timing generator gives me 10 degrees advance starting @ 16.8inhg , 5 degrees @ 10inhg and down to zero advance @ 4inhg.

 

[David Robinson]

@W427 Wowza! That’s exactly the answer I was looking for. Thank you for taking the time to write it out and making it clear enough for my monkey brain.