....
GM Top cylinder cleaner OR Sea Foam. Both work well for this.

Move vehicle OUTSIDE!!!

Start engine let it warm up.
Pull off a vacuum line ABOVE the areas you want to de-carbon.
VERY IMPORTANT STEP.

Now with the engine idling allow the engine to draw 1/2 - 3/4 of the can
of cleaner into the hose. When it gets to that point invert the can and
stall out the engine with the cleaner (it won't lock up, just quit
because of the mix). Now let it set for 1/2 - 1 hour. When you start it
back up you will get a HUGE cloud of smoke with a LOT of carbon in it.
Make sure your exhaust isn't pointed towards anything you want to keep
clean. Run it a bit until the smoke clears up, then change out the
oil/filter, you may want to do this again after a couple days. There
will be a LOT of carbon and crud flushed into the oil.



--
Steve W.

ok, so top cleaner or sea foam - right..... how do these things go about
doing their job? I ask because the carbon in question is not inside the
combustion chamber - so putting the goop into the intake will do nothing -
....

I can vouch for the sea foam trick. My neighbor is a mechanic. He "tunes up"
a lot of old cars this way. I use it once/year on my old 8N tractor. When
your engine is hot, sea foam really dissolves carbon.

Karl