Using propane to diagnose a carb problem...

[Cal69Chevy]

As some of you are aware I've been having a problem with the engine sputtering off idle. I was talking with a man that rebuilds carbs and he gave me this 'tip'.

He suggests that I reproduce the sputtering by putting the truck in drive with both the emergency and operating brake on and accelerate to the point where the sputtering starts. This is where it gets interesting. He suggests having a hand held propane torch available and positioned so propane can be released into the carb. just as the stumble starts open the propane valve releasing propane into the carb. If the stumble goes away then it is a fuel starvation carb problem....if not it is likely a vacuum adv. problem.

Sounds like it might work. Have any of you ever tried this? The truck has never backfired so I feel reasonably safe from being blown up...however it's never run on propane before either!