with the head off, what chemical is compatible with oil that i could use to clean all the [censored] off the parts? preferably something i could spray it down with that won't hurt seals, etc.? want to clean off the valves and combustion chamber/intake/exhaust port areas, as well as what's under the rocker cover like the lifters, valvesprings, and the internal head casting itself. mainly just concerned about the crystalized oil bits but if it takes off the varnish too that would be nice. thanks for the information!