Johnny Roadkill wrote:Disconnected at distributor and hose blocked...or pinched closed while connected.
You're setting "static" advance and don't want vacuum or mechanical advance fudging the setting. There shouldn't be any mechanical advance at idle but there will be vacuum advance if you don't disable it. If you don't block the hose the idle will be higher and may hunt as the manifold vacuum will suck in extra air and lean out the fuel mixture.
Cheers,
D
I have to disagree a little bit, mostly due to the fact that at idle vacuum at the distributor is negligible and won't affect the timing setup. Vacuum develops under throttle conditions when you're demanding power of the engine.
So the bottom line is that the outcome should be the same.