[njsteve]

The biggest crud retention device on a Pontiac engine (assuming there's a Pontiac and not an Olds 403 under your hood) is the valley pan. If the valve covers are filled with gunk, then the double-walled valley pan under the intake manifold has around 5 pounds of carmelized/fossilized goo inside it. The only way to get that out of there is by removing the valley pan and hot tanking it. Or replacing it, of course. That gunky PCV you mentioned is a red flag for the valley pan syndrome.

If you have access to a boroscope you can do an exploratory colonoscopy in the PCV oriface. It will probably scare the crap out of you. (no pun intended) [img]<<GRAEMLIN_URL>>/grin.gif[/img]

The last thing you want to do is run some kind of solvent that would partially dissolve that brick sized, iceberg of crud and have it continuosly flood your engine with crap.

Best idea would be to remove the valve covers, intake and valley pan and have them hot tanked. The intake itself can also store a bunch of crud in the internal heat riser crossover.