Exhaust Valve Crud

[chassis 33]

I've just done an engine swap on an old motor of mine with a known good used engine. As a precaution I whipped the heads off, to check the valves and pistons were as good as the engine sounded, and the bores were in good nick.

What I did notice was on the combustion face of the exhaust valves was a but of a crusty deposit, that scrapped off easily enough and was a off white colour. I've noticed it before on other engines, what is it and what caused it?

Regards
Iain

[Trooper2]

It sounds like ash deposits, that come from burning oil and/or fuel additives.
You would usually find some on the spark plugs as well, probably not a concern unless there is allot.

[steve_D]

Todays fuels have many additives to reduce this but years back it was common to have an engine 'de-coked' to remove these deposits which would have built up on all surfaces. I have seen engines where the exhaust port has been all but closed off with the buildup of coke on the back of the valves and valve stem.

Steve

[chassis 33]

Thats what I thought, not a problem, cleaned them off!

Regards
Iain