For all of you that have gone out to port you plenum and runners and have looked in you plenum. You see an astonishing amount of carbon build up. Well heres how to clean it all up. Go out and buy some good engine degreaser & throttle body cleaner (make sure it has a little red hose). Now just coat the inside of your plenum and runners with the degreaser. Dont go sparingly with it, make sure its nice and coated. let it sit fo a good 15 minutes and rinse it out with a hose making sure its all out, and just hit it with some throttle body cleaner and just watch it all blow away. Leaving you with a very clean and tiddy plenum and runners. I have heard this gives u a tad better Throttle responce. (mixed opinions of course)

enjoy
J

 

i think this method is fairly widely used...thanks for the method though, bought a used lt1 intake and i'm sure i'll need to clena it up...

 

Just don't spray the degreaser into the plenum, then get distracted with a phone call, forget all about what you were doing and go to bed, 'cause the majority of HD degreasers out there eat aluminum.

 

I cleaned mine with that $.99 carb cleaner from autozone. Worked great cleaned it in twenty minutes. I did find that the expensise $3 gunk or gumout(can't remember) carb cleaner won't phase it. But two cans of the cheap stuff and no carbon left...

So I did a little test. Bought every kind of carb cleaner and tried it. I found that the cheap stuff in the red can worked the best. Forget the degreasser It failed my test. You have to rinse that out. Try two cans of cheap carb cleaner and the carbon just vanishes. No need to rinse looks like new...

 

I thought it was pour some gasoline in to the plenum, let it soak, pour some more, then throw match in from about 5 ft. away. Is that not right?

 

send it to me and i'll sand blast every bit of carbon out
PM me for pricing.

 

That would be fairly easy, since I've never seen carbon in my plenum, only varnish. Most of what accumulates there is atmospheric dust, not combustion byproducts or carbon. When a hot engine is shut down, any remaining fuel in the intake runners will evaporate, condense on the plenum walls, then evaporate again. The fuel residue and heavier fuel additives that evaporate last (if at all) effectively glue the dust to the inside of the plenum. Once the engine is started again and the plenum heats up, it simply gets baked on like carbon deposits.

If anyone ever takes the time to measure the thickness of the deposits, you'll find that cleaning it all off to a pristine condition is not only without much flow advantage, but is an excersize in futility. In about two months, the deposits will start forming all over again. I'd rather spend the time with a die grinder to do some real plunum cleanup.