I have a QF carb on my engine. It is a 4 barrel and I think it's a 850 but not sure. If anyone knows how to recognize it, that will be a big help. I don't see any numbers anywhere on the carb and not sure where the paperwork went from my builder. Anyway, I need to change the power valve. I have the bowl off but how does the metering block come off? Tap/pry off? I want to make sure before I try to do anything.