guys

what are the symptoms of a blown power valve on a holley carb? what problems may it cause?

Really rich at idle. I thought I seen a post on here saying that Holley says that carbs made after I thought the late 80's should all have PV protection from the factory.

rich idle like Dave said. often you'll be able to screw the idle mix screws in all the way without killing the engine.

inspection: pull a lower bowl screw out, let the fuel drain into a paint can lid or whatever you can find that will hold it. pull the rest of the bowl screws and pop the bowl and metering block off. look at the back of the PV, it should be dry. the vacuum chamber in the main body should be dry too. sometimes if you bump around the accelerator pump getting the block off the carb it will squirt a little fuel into the chamber, but the back of the PV should be dry. If it's wet in around the diaphragm it's probably got a bad diaphragm.