Testing the HiRev 7500

It's amazing the legs some of these old "rules of thumb" have had.
There was a time. A time when points distributors were the norm, dual points were king, when tossing the heavy spring and running fast advance to a limit, could be the hot ticket to a little more power in the quarter mile.

The fact is that most magazine writers and even some speed part pushers couldn't, wouldn't and won't learn from the top racers and the go-fast operations at the big 3, err 4.

Guys who actually need results at high rpm know better, sometimes from hard experience.
As two of you posted here:
https://www.forabodiesonly.com/mopar/threads/lets-revisit-timing.499590/post-1973619145
I don't see a big issue setting up a curve when the same triggering device is used, but the importance of getting beyond setting timing at "idle" and "all in" can not be overstated.

I've posted these before it but it will be good to do so again.

Mattax said

MP setup their race distributors (aka tach drive distributors) for easy starting and to maintain high rpm timing flat or very slightly advancing. (graphed here) They basically accepted idle timing as somewhat unstable because they didn't think it was that important - at least relative to the other two goals (easy starting and top rpm performance).

The reasons to put a curve in the distributor are twofold.
1. It will likely allow the engine to run richer and stronger at idle. The better it runs at idle rpms then the less time for the carb to clear up when throttle is opened.
2. The top end should continue advancing mechanically so as to avoid the retard that comes naturally with most electronic ignitions. (If running dual points then not needed.)
As illustrated in the two videos posted here. lets revisit timing

https://board.moparts.org/ubbthread...mallory-unilite-timing-issue.html#Post2488599

Click to expand...

For racing at higher rpm the right curve for an electronic ignition has to take into account the slew rate. As mentioned above, my coworker who had been running stock eliminator had learned this the hard way when he removed the secondary spring from the Direct Connection tach drive distributor.
Tuner described the same lesson except it was with a GM.
"A-B-A-B it was faster with the GM dual-points distributor, even though the spark energy was higher with the electronic, a GM Magna-Pulse, and the electronic had the same “curve” except for the retard after the “total” was reached at 2500. Jenkins book “The Small Block Chevrolet Racing Engine” details the high-RPM curve and explains his reasoning"

And for those who like to experiment with computer simulations, I posted some locked timing, vs. basic ramped timing power comparisons using Dynomation 5. lets revisit timing post 41