Alas, I think my dear old Shorrock has come to the end of its life
Although it certainly wasn't new in 1962 when I was given it by somebody from Allard, it tested the brakes and pepped up my mother's Morris 1000 traveler for a couple of years, some times showing almost 10lb boost as the valves bounced.
Since then, with home made brackets and an A35 manifold, it has blown many minis, but despite several rebuilds, the 7lb boost (due to a smaller crank pulley on minis) was down to 4lbs last Monday.
I stripped it today, and sadly, after countless thousands of miles, it is just worn out.