More power for my 16H!!

was impressed how quick a 1929 norton was hustling round goodwood on sunday how fast you really need to go?

Weren't pre-1929 16H lighter and quicker than the post 1930 bikes?

Funny thing about pistons - my friend has a 16H piston he once intended to put into his ES2 to RAISE the compression ratio. Mind you don't do it the wrong way round...!

Someone here will hopefully know the respective heights of gudgeon pins below piston crowns...that would be useful data for all Nortons.

I did fit a 18H piston to a 1953 ES2 to raise the compression. The 16H piston is domed, whereas the ES2 one has a flat crown. Of course, to fit a 16H piston you have to mill valve clearance pockets and shorten the skirt.

If you want to raise compression on a 16H I think you'd have to mill the cylinder head.

Does the 16H head have a big cavity over the piston? If so, I wonder why? Squish effects were well enough known by the 1930's, weren't they?

I imagine the 'best' combustion chamber on a side valve has as nearly as possible no space over the piston at TDC - giving the biggest possible squish area - and what volume remains should be over the valves where space is needed anyway to allow the valve heads to rise off their seats. Unless and until I remove the head from the 16H I am currently getting back into service I don't know how close the piston is to the head. But why did they complicate spares manufacture by doming the 16H piston when they could have use a flat piston and a flat area on the head just above it? (or made a smaller cavity in the cylinder head?) Or did domed pistons only arrive post-war when 'pool' petrol was finished with?

I suppose if I want a faster bike I'm better off buying a modern machine that I would be by filling cylinder head cavities on post-vintage side valves with weld...

The outer edge of the 16H piston comes up flush with the top of the bore at TDC, the dome sits above this with minimal head clearance on the side away from the valves, and leaves a vertical gap for gases to get in/out of the bore on the valve side. So i doubt that a flat top would be a step ahead.

There is a 16H near me which has had the head planed - it does give it more go but an OHV it is not. Have read elsewhere that 40 thou minimum clearance over the piston is needed and i forget whether 7:1 or 8:1 comp ratio was the recommended maximum.