Regarding timing, rpm, load, and torque converters, I'll offer some snips and links for discussion.
In response to my questions about timing, Tuner wrote:
"An engine used for circle track or road race is operated in a fully thermally soaked condition, as is a highway car, and cannot stand, does not require, the "all in at xx??" curve, they want the best timing for best torque at the torque peak RPM and then continuous advance to more timing which gives best power at the power peak. The rate and amount depend on C/R, chamber design and manifold pressure, restricted carb or not, etc."
With respect to too much vacuum advance when cruising:
Q. What happens if the maximum vacuum advance is not limited?
A. "It feels like a lean miss or surge. It may be an occasional hard miss like a bad plug wire, or a gentle surging that sort of nods your head. A common euphemism for the sensation is "trailer hitching" because it feels sort of like a 2" hitch on a 1&7/8" ball.
In all circumstances, the object of ignition timing is to peak the cylinder pressure at or near 15-20 degrees ATDC."
In sum:
"The advance schemes I suggested...will work OK for most engines with old school combustion chambers, Mopar, Ford or Chevy. The outliers are the fast-burn chambers whether new or old. Pump gas makes it particularly obvious because it is so easy to get knock. A fast burn chamber will need a less mechanical (RPM compensated) advance, but may need correspondingly more in vacuum (load compensated) advance, particularly if a large amount of cam timing overlap results in more EGR. The need for vacuum advance is related to the slower burn of lean A/F but the effect of exhaust dilution at high intake vacuum is a significant reason for requiring more advance."
In response to a question about setting up an FE, Tuner had pretty much the same thing to say:
"The FE and many other engines want more timing after the torque peak RPM than the amount which gives best torque at the torque peak. Your engine with the 224°@.050 cam will have peak torque at about 3000 RPM.
If you are using high octane fuel, like Avgas or race gas, it is not so important to slow the advance curve to avoid detonation although it will probably run better if you do.
Drag strip only use a fast curve is tolerated because an engine is never loaded at mid RPM for sustained periods like it can be on the street or oval and road racing. The longer duration of load at any RPM increases the temperature of chamber and piston surfaces and the heat speeds combustion and so does not require or tolerate as much advance as the same engine used in only few second bursts at a drag strip."
I know most people reading this don't know Tuner (except YR) so as far as you know he could be a keyboard guy making stuff up. That's why earlier I mentioned a few of the road race cars he helped the owners with. He prefers to go just by Tuner on the internet, and I will respect that.
Bruce "Shrinker" Robertson" Regarding initial timing:
"If you enrich the mixture at idle it will require less timing and the volume of gas expelled from the chamber will be greater (because there is more fuel in the cylinder ). The greater volume exhausting resists reversion backwards up the exhaust port therefor it actually runs with a cleaner chamber. Funny stuff isn't it"
"BUT what you have to do is enrich it correctly with the right processes in the carburetor, sometimes it's not just a matter of winding out the idle screw or changing the IFR. Every engine has a design to it and Chrysler's are a bit different to the other US products, they are not chevs or fords, they are better. They have better combustion and its not necessary to follow the rules of the hotrod industry, as the industry is very Chev orientated. Now what i just said should get plenty of people jumping up and down( hopefully in fun)."
from here: Motorsports Village • View topic - Initial timing
Shrinker may make your brain hurt, but I appreciate his way of approaching thing even though I'm not even in the same league of understanding, experience or knowledge.
"Tuning is the process of visualizing the progression of combustion and its conversion to mechanical energy."
He provides a stage by stage explanation of the combustion in this thread about dynoing a 440. Reading this you can see why even a single groundstrap shadow can play a role in flame development.
Motorsports Village • View topic - Dyno time
Finally, here's a case (non-mopar) where he warns that cruise timing and AFR could cause problems when going to full throttle. But I don't think 71GSSDemon's engine is in this situation but maybe worth keeping in mind.
"Your engine has a big cam for that low a compression so I'm not going to get into helping you tune it. My advise is to be careful about the tuning because if you go the wrong way you will end up making NOx at light loads and damage the engine when you stomp on it. If you run it rich it will be safe and the reading on a WB cannot always be trusted. If you used a gas bench and a dyno you will find that engine has plenty of unused Oxygen in the exhaust and thats a bad thing, it means there is unused hot Oxygen's left in the cylinder and thats dangerous,thats why you need to be rich and no where close to stoich. Pick the wrong ign timing at cruise and you will have hot carbons glowing waiting for you to open the throttle and give you some preignition woes. So id put up with a rich cruise, maybe not as rich as you describe but more in the 12.5 12.9 range. I wouldnt advise to go leaner than that unless gas bench and dyno confirmation showed otherwise."
http://motorsportsvillage.com/forum/viewtopic.php?f=6&t=915
