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It is called a manifold heat damper / riser. Its function is to direct exhaust heat to the intake manifold / carb are to preheat the incoming gasoline vapors for better combustion during cold temperatures. As the engine warms up the bimetallic spring loses its tension and allows the valve to 'open' and direct all the exhaust out the system. If you only drive the car in warm weather you probably can eliminate it without any adverse affects. ( It may take a bit longer to warm up and have good drivability) If the valve was stuck closed, directing hot exhaust towards the carb it could cause vapor lock and poor performance. Does the valve move freely?

Thanks Jim.
Yes it does move freely.
Living in central west of NSW in Australia means that most driving will be in warmer/hot weather. Being a convertible dictates that as well!
Will see if its possible to rebush the shaft to stop the exhaust leak, otherwise will delete it and see how things go.
Thanks again
Simon

Simon,
I have a 232 engine in my Pacemaker but it has the same valve in the exhaust as yours has. Mine, however, was stuck and no amount of penetrating oil and hammering would unstick it, so my mechanic took down the exhaust pipe and with a pry bar, bent the valve out of the way so it wouldn't block the flow of exhaust gases. As I only drive the car in warm weather, that doesn't have any adverse effect on driveability, but I have noticed a decrease in sensitivity to heat on the fuel so there isn't the hot weather problem as before. Less heat to the carburetor helps and as the fuel line passes by the manifold, if the manifold is not so hot then that helps things to work better. But, you are lucky that yours is not stuck.

Geoff Blake

Hi Geoff
Yes not being seized made it easy to remove, hardest part being undoing the exhaust bolts!
Haven't driven it yet but hopefully won't affect things too much.
Regards Simon