At speeds of over about 30 mph the reverse and hook up pedals on our Model 607 vibrate excessively back and forth. Everthing seems solid enough when the car is at rest, can't feel any lost motion in the pedals and linkage. Engine spring hangar seems tight, might be engine out of balance forces. Engine will be doing about 600 rpm at 30 mph with 32 inch tyres and 30:56 gearing.

Any suggestions as to cause, adjustments?

This problem can be caused by worn valve seats in the engine.

Thanks Tim

Engine has run only few thousand miles since a complete rebuild, hope its not damaged valve seats! Cylinder oiling rate is currently about 1 US Gallon per 500 miles (or roughly 130 miles per litre) , using Hallett CTROS 1000 oil. Wonder if I should increase the oiling rate? The car does a lot of relatively short journeys, of 10-15 miles.

The pedal vibration does not seem to occur on hills when throttle is open much wider, higher steam chest pressure but slower speed.

Peter

sounds like the dog on your link arm of your engine is not staying in place, the edges could be worn / rounded off.

Rolly