Originally posted by crash guy
close the needle valve until you can hear the most rpms, then open it up until its rich and smokey. run 2 or three tanks through it.
That advice would work for ringed engines. It's about the worst thing you can do to an ABC engine and I'm pretty sure the Magnum is ABC. They need to get up to temperature fast. Running them rich and therefore very cold can ruin the cylinder bores.
The type of engine matters a lot though the precise make doesn't.
Steve