Identify this noise please!

[gjz30075]

Yep, lots of rags helped.

[terryp]

And the answer is Exhaust leak!

I went through the archives and there was a suggestion of either using a glove or a hose. Tried the glove first and my heat resistant glove turned out not to be quite so heat resistant. Tried the tube and nothing on the headers but nearly burst my ear drum on the join between the cast iron manifold and the exhaust.
There was no stain, no black blow or anything.

Well I have a lovely job for the weekend

Thanks to all, at least it isn't serious and I can advance the ignition a bit more
Terry

[webbslinger]

I'm a bit late to this thread, but regarding the question of if it is a broken valve spring, new is when they often fail if they are going to. In my limited experience, the engine can run fine up to maybe 5k or so with a broken outer spring with just a bit more noise than usual, but possibly not really noticeable up to that point. But with more throttle past 5k there isn't enough spring force to keep things together and you will start hearing lots of valve clatter. There may also (probably will be) be missing / rough running at that point. If it is a broken spring you can feel it by pushing down on the followers until you find one that feels weak. Different springs probably react at at higher or lower rpms and I haven't experienced a broken inner one.