I sprayed the underside of the hood with undercoating and it is still tacky after a couple of days. Did I screw up in using undercoating? A mechanic told me to use it because it would deaden sound as well as keeping the hood from rusting. ?????

 

You used it out of a spray bomb? I wouldn't spray that crap anywhere on any car I own. When I restored my '69 Firebird I used professional grade in the rear fender wells, and it came out really nice. If you decide you don't want that stuff there anymore you're going to have a heck of a time removing it. Unless you park your car outside, hoods are really very likely to rust anyway. IMO, yes, you used bad judgement.

 

That stuff is nasty, but it should dry.

 

Maybe you just put it on a little thick. I agree it should dry. Rubberized undercoating can feel like it is tacky when in fact it is just the soft nature of the product. Leave it parked with the hood up for a few days.

 

Check to see if it's tacky before the engine runs. the heat may cause it to tack up after the engine runs.

 

I don't know if it's rubberized, but it is petroleum based. Used by the military.

 

Almost everything is petroleum based. It should say on the instructions/can/whatever if it is rubberized.

 

If this crap never dries, what will remove it?

 

Chemicals! I hope you don't have an engine fire with that stuff under there. I think bed liner would have been better. Take the hood off and pressure wash it. That may remove most of the undercoating. You may have to use acetone to break up the rest. Is the paint on top good? If it is be careful with the chemicals.