Effects of Total Ignition Advance

[colnago]

This is just an FYI post. I've been doing a lot of experiments with my ignition timing. The last was in recurving my Duraspark distributor. I switched the slots from 15L (30 degrees at the crank) to 10L (20 degrees). With this, my initial advance was 18 degrees BTDC, to put me at 38 degrees total. I also changed to lighter springs in the distributor, to bring in total advance by 3000RPM.

Recently, I've been reading about the pros and cons with the timed-vs-manifold debate for the distributor. I continued my experimenting today, and put the distributor vacuum can on the manifold port (total vacuum advance while idling). With my current vacuum can, I get 13 degrees advance at 15"Hg. Because of this, I lowered my Initial advance to 12 degrees BTDC. The result is that I currently have 32 degrees BTDC at 3000+ RPM, and 25 degrees BTDC at idle (600RPM).

So far, buzzing around town is fine. There's no bog when I accelerate from a stop (when the idle vacuum advance goes to zero). However, at highway speeds, the old girl is gutless. She really liked the 38 degrees BTDC, and does not like the current 32 degrees BTDC. She maxes out at ~65MPH, where she pulled much stronger with the higher advance before.

In short, the experimenting continues. Next week, I hope to install vacuum/tach gauges, to see what's going on when I drive. I also figured that I would drive her as-is for the next week, since a one-hour drive isn't enough to determine anything.

This post wasn't intended to ask any questions, but if anyone has feedback or experience, I would be very interested in what you have to say. Right now, my current thought process isn't that the Ford manuals give timing specs for optimal performance, or that we want to put In as much timing as possible. Instead, there is a "best" timing curve for performance, and by adjusting initial, mechanical, and vacuum advances, we should be able to attain better-performing engines. Also, what works for my engine is not necessarily what works for your engine.

Joseph

[1972hiboy]

Hey Joseph, Dont know if this helps at all, or maybe you have seen this or read it when woods put it out. But i think it is a handy article to check out when the who timing question for FE's comes up.



http://ww.fordification.com/forum/viewt ... =3&t=62960

[colnago]

1972hiboy,

I've not seen this write-up (I do most of my searching during breaks at work, and I can't access FORDification from my work PC.

I do recognize the vacuum graph, though. I think I found it on a Jeep forum. I've read so many things, though. The bottom line is that I'm learning that the engine will tell me what it needs. Also, for a street engine, you don't necessarily want/need max advance, you need the CORRECT advance at all times, not just WOT. And since I can't get it all in a 50-year-old design, I have to learn where I can compromise.

The adventure continues ...

Joseph

On edit, I just finished reading your link. Sounds like Woods and I are on the same wavelength. All of these numbers are just that: numbers. The various types of advance - initial, mechanical, vacuum - are just ways of tuning your engine to best meet these compromises. Every situation is different - different engine, different altitude, different gas - so each owner needs to tweak their ride differently. For me, I use the books as a guide, but not a limit. After all, the gas we use today is not the same gas we used 50 years ago, so why are we sticking to numbers that were published 50 years ago? My truck deserves better.