Bought a motorhome on a 1989 P30 chassis. It has a 454 cu.in. engine. The engine has 120000kms on the clock. It seems to run fairly well but not as smooth as I would like. The inside of the tail pipes are black and sooty. The dual mufflers appear to be inexpensive and they show severe heat marking. Any ideas what I need to do?
Pull the plugs, they're likely sooty/loaded with carbon as well, and the combustion chamber may be too. Google all the reasons for carbon build up in an engine. You'll want to go over the intake carefully, the PCV, EGR, eliminate any vacuum or intake leaks, make sure air/fuel mix is proper and not running too rich. Combustion chambers with carbon build up tend to get hotter, further exacerbating the condition that caused carbon build up in the first place and leading to more carbon build up.
Is this an injected engine or does it have a carburetor?