454cid
Sooper Pooper
I've seen pro detailers use the pressure washer inside, but never pointed at the dash. Our GM's sister would bring her car in for a detail and that's how they'd have to get the burgers out of the carpet. When a customer thought they'd get one over on the dealership and left a pile of fish guts under the rear seat of a Suburban in summer, the detailers unbolted the rear seat and pressure washed it out. Half an hour's work and you'd never know there was a fish back there.
I've considerd doing it to my truck's dash, since I have no carpet anyway.... I'd pull the seat. I'd close it up with the dehumidifier and fan inside afterwards. I think. Obviuosly, I'd have tp be careful of the speakers. I get lots of stuff wet that "you're not supposed to". Many times it's the length of time, not being wet at all, that hurts.