Carb/timing procedure

I will have more to say later, but for now:
- it is rare for MVA to not provide a benefit over PVA. Exceptions would be locked dist, a ton of initial advance ort elec box that advances idle timing.
- Ch did use MVA. Through the 1970s decade. With engines loaded up with emissions crap, engines ran hot. Sometimes too hot. So at a pre-determined temp to prevent overheating, a temp switch switched from the useless PVA to MVA.....
MVA uses the A/F more efficiently at idle, reduces engine load & an efficient engine runs cooler...