this is a rebuilt head a6 with 70-80k on it. Am I wrong to assume that leaking valve guides caused this? what can i use to get this out? the exhaust valves are just as bad.

 

I also started to scrape it off with a screwdriver and it was white underneath the thin black layer

 

wow i guess everybody pays someone else then

 

seems like alot of carbon build up. but being that i dont know anything about the motor i couldent tell you. but low quality fuel is the number one reason too much fuel is another. you can clean it with spray carb cleaner or when you get the head back on use seafoam or a bg induction service to clean out the rest of the carbon.

 

the head wont be going back on, it was the old motor. the carbon wasnt bad on the piston or anywere else on the head,just the exhaust valves with #3 being the worst. the

 

I would agree with the valve stem seals leaking. Ash deposits from burnt oil show up as a white chalky buildup.

To clean up the valves, wire brush on your bench grinder works like a charm. To clean up the bowls a wire brush on the end of your die grinder should work.

It may be easier to hot tank the head but I don't know if hot tanking the would get rid of the ash but it's maybe worth asking the machine shop if it will.

 

is it common for only the exhaust vavle to start leaking

 

yes because of the exhaust valves run so much hotter than the intake side.

 

could be the valve guides or the valve stem seals where installed wrong , ie intake seals on the exhaust side , they cant withstand the high temps of the exhaust so they give out .

 

any one know how toet it off?