Ok then
Make sure the Vcan is hooked to the sparkport. With good combustion chambers, tight Squish, and/or aluminum heads; detonation will not be an issue. The Vcan will only work at part throttle, and will vary the timing according to the throttle opening. The harder you step on it the more timing will drop out, and it absolutely cannot work at WOT. At a cruising RPM of 2200, the timing will be fine with a minimum of 40/45* to a maximum of 55/60*, TOTAL. That's initial, plus centrifugal, plus Vcan. he crappy your chamber, the more it will like. The more your engine accepts, the leaner you can run it. Pretty soon you will be getting fuel mileage in the hi 20s. Ok; maybe not you, but I did,... with a double overdrive pulling like 1550rpm@65mph. That was a final drive of just under 2.0
Ok since you asked about idle-air bypass;
This is air you might need to introduce into the low speed circuit, to satisfy the engines craving for air,while maintaining the T-port sync.Click on the little blue M in my sig for a better understanding.
This air has to be introduced near to where the transfer ports are, so that it has time to mix with the A/F charge entering there, and be fully homogenized by the time it gets into the chamber.
The bigger the cam, the more bypass air it will want. My HE2430AL did not require any bypass air. So yes, closing up the secondaries tight but not sticking should reduce the rear idle fuel to zero.
If you advance the idle-timing, the idle speed will go up. The first response is to back out the curb idle screw. But doing that will lower the throttle blades on the transfer slot and that will reduce the fuel being delivered there. So then the next idea would be to increase the mixture screw opening so she will idle again. And that works. At idle. But as soon as you step on it, the beast goes lean, and she hesitates, maybe even stumbles; until the transfers come back on line. Sound familiar?
So, the transfer slots have a minimum operating relationship with the throttle blades. If a decent idle speed, and tip-in cannot be obtained at this minimum setting, then we have to figure out how otherwise to make it happen. This is where idle-timing and bypass-air come into play.
