Decoke soak

[David Witham]

Some years ago I used to compete in sprints and hill climb. After rebuilding my cylinder head using the improved valve stem seals I had problems with exhaust valves sticking. Peter Burgess suggested that I ran the car with no exhaust valve stem seals at all. I took his advice.

This winter I have removed the head from my B on a while I am at it basis as the car needed a new exhaust system. The exhaust valves have heavy black deposits on them. While I can remove the deposits from the stems and the backs mechanically I don't want to damage the seating surface.

What could I soak the valves in to clean them of at least soften the deposits?

I had thought about caustic soda.

I am planning to use ordinary stem seals on the exhaust valves when I reassemble the head.

[Vic Butler]

I remember caustic soda was used way back in the 1960's to remove oily deposits from 2 stroke motor cycle silencers. It's OK for cast iron but not aluminium. Be very careful handling it and use in well ventilated places.

[Peter Cresswell]

I've always cleaned up the valves by clamping an electric drill in the vice and putting the valve in the chuck. Using strips of cloth backed emery cloth and a old blunt ended screwdriver the valves look like new in no time. Just take care to wear goggles and don't have loose cuffs that might get caught. You can take care not to touch the seat face, but you should grrind the valves in again after the decoke.