I totally agree with Chuck. IMHO an engine with lots of varnish on it means that it's been taken care of for it's life. That varnish tells me that the engine has been ran nice and rich in it's life and should be a good running engine. On the other hand, an engine that's used and is all nice and clean make me wonder what it's trying to hide!!

As was said above, never EVER use the crock pot of cooking food again. Use this outside because the vapors given off are toxic so you should have plenty of ventilation. Take apart the engine enough to remove any rubber parts, plastic parts, and any gaskets. Place the engine parts in the crock pot and pour enough antifreeze in to cover the parts. Turn the crock pot on low and let them sit in the heated antifreeze. How long will depend on how much stuff you have on your engines. Check periodically to see if the crud is loosening up. Use an old toothbrush (once again, don't use it for your teeth ever again) to see if it's loosening up. Once the crud starts breaking up then use the brush to remove it from your engine. Once you have the engine clean rinse away the antifreeze and then put a light coat of after run oil on the internal parts of the engine. You can can re-assemble the engine.

One point, you have to use the green anti-freeze. The environmentally safe stuff won't work for this.

Hope this helps

Ken