I have a 1955 chevy, 6 cyl with 54,000 original miles.  As far as I know the head has never been off the block.  I am having a problem with carbon on the spark plugs.  I tried a hotter plug but that didn’t help.  I was told by an old timer that back in the day there was a product sold that was slowly poured into the carb and that broke up the carbon deposits.  He also said they sometimes dripped water into the carb for the same cleaning effect.  any thoughts on either method and is there a product on the market to help desolve the carbon in the head.

I would guess that your old timer was referring to Marvel Mystery Oil.  It was developed in 1923 to remove the carbon deposits from the Marvel carburetor and still does an excellent job of removing carbon in today’s high performance engines.  There are a few ways that you can use Marvel Mystery Oil to help solve your carbon problem.  The most recommended way is to add 4-ounces of Marvel Mystery Oil to 10 gallons of gasoline.  Do this at every fill-up.  If you do not drive the car every day, remove the spark plugs, pour 2 tablespoons of Marvel Mystery Oil down each cylinder, replace the spark plug and leave set for about 48 hours.  Thirdly, you can slowly pour the Marvel Mystery Oil down the carburetor being careful not to stall the engine.  The long tern solution is to use the Marvel Mystery Oil in your gas with every fill-up.

There used to be products both liquid and aerosol that did indeeed contain water.  This emulsified water was either poured into the gas (liquid) or sprayed down the carburetor (aerosol).  The theory was that when these products were burned or combusted, the water turned into steam and in effect you were steam cleaning your engine.  I don’t think there are any of these products still on the market.