I was doing some work on the Z28 and I forgot about how bad ass this stuff is. It's made by LPS and called Presolve. It basically will blast away any and all baked on grease that you're trying to clean. No brushing is needed. It is some really neat shit. The stuff is kinda steep, but totally worth it. My brother used to get it from the airlines' expired throw aways, but my free stuff supply chain is no more. Try this stuff on a car or ATV and you will see what I mean:
http://www.lpslabs.com/product_pg/degreasers_pg/PreSolve.html