Originally Posted by kenneth
Well, pretty sure seafoam will do squat
Picture a thick layer of grease that caked on the valves as well as intake tracks over time, and rubbing with a tooth brush won't do anything, but instead you have to blast away with a very abrasive material (enter crushed walnut shells), chemicals have little chance to work, unless you're pouring acid in ......
I'm also very sceptical about the seafoam. I was looking at youtube and I saw guys pouring 1/3 of a 1L bottle in the valve cover (good lord), 1/3 into the gas tank, and sucking up 1/3 into the crankcase positive vacuum. Driving 30km
and then doing an oil flush.
The only methods I know of is fine brass brushing with approved solvent in the intake, or dismantling the head entirely and cleaning the parts individually. You can be sure there is more than just intake valves and ports that are gunked up.