Now, in the case of Kyle's problem, though- I do not see the difference between front or rear limiting having an affect one way or another on the pinging he's getting at throttle tip in. The reason I believe this, is the advance is at the max while at a light throttle cruise. It wouldn't matter if the can came in at 2 in/Hg or 5 in/Hg or 10 in/Hg- it's all in at the throttle setting where he's getting pinging at tip in. That is a function of TOTAL timing- either by the vacuum can, or by the total mechanical timing and the tip in point of the vacuum advance can wouldn't change that.
Good point I agree...if the can has its full advance in by say 11- 12 "hg then coming off of a 20" hg pull at cruise will not drop out the vac advance with a light throttle application unless the HG pull drops below 12" or so, but i wonder about his 20" at cruise as I stated before it seems high, mine is about 14-15 at this cruise RPM of approx 2300 and any throttle be it just a touch drops it down enough to dump out some of my vac advance but each setup is different so it all depends...
So all that said, hopefully my earlier dismissal of Custom's testing being wrong will be forgiven. Fact is, it is right on. [/QUOTE
Thanks for that cobalt, nothing to forgive but I get what you are saying
I seems that we could almost start a separate category here on HRBB and call it tuning or something like that. I mean there is the base engine building and design considerations, variations, technique etc etc but when it comes down to making our engines work on the track or road its all in the tuning and ignition/carb setup could almost have its own header...food for though any how.
I am not sure if anyone has seen this spread sheet that is out there I don't know a bunch about it and it may be for ECU controlled spark but I was messing with it and changing some numbers around kind of cool, it shows the relation ship between initial, mech, and vac advance on total advance....