A quick poll: The Plus 8 engine mounts are in 3 pieces, the top mount to the engine, the rubber bit in the middle and the cast bit to the chassis.
On your car, is the rubber mount bolted to the front of the chassis mount or bolted to its rear face?
Did the factory have a set position? I suspect most are mounted to the front but my ex race car is to the rear and wondered if this was a way of shifting weight rearwards a little.