Ron, I swear by
Westley's Bleche Wite I had some brake backing plates on my jeep that had about a half inch of 60 year old petrified crap stuck to them.
Someone at the jeep web site recomended this stuff. They said it was the strongest cleaner you can buy withour a license.
Not only did it clean off the crap with very little elbowgrease, but it removed half the old paint.
You can buy a spray bottle for a couple of bucks and give it a try. It is very caustic, so wear rubber gloves. And, it will curl your nosehairs, so use it outdoors. Don't bring your chassis into the living room.
