So long as your engine is up to normal operating temp...you need only get up to WOT for enough time to stabilize...which is usually only a few seconds. Run WOT for 10 sec and without touching the throttle...kill the ignition. I'd pull at least two. One from each head.
only if you have a backwash wave coming up behind you , Do a quick turn , then chop the throttle and ign.
But using todays fuels with no lead its hard to get an accurate reading . As long as your between snow white, (way hot) to deep black(way cold) your fine. Oily is what you dont want to see
What you want is for the plugs to appear like they're covered with Hershey's cocoa powder.
Even with unleaded fuel, you can get a good idea of your A/F mixture, timing and heat range from your plugs. The "art" of plug reading has gone to the wayside more because of EFI/ECU management moreso than the lack of lead. If you still have a carb then it's a good bet you'll be able to get a good "read" at whatever throttle angle you chop the ignition at.
