I know quite a few people with Manx's who aren't racers and don't race them. They seem to go everywhere in a van to be put on display at a show, or riden around in a parade, probably used once or twice a year. I am determined it's not going to be just a parade queen, if it's road legal I can take it out for a blast whenever I want. I am booked to take it to the I.O.M. GP next year and hopefully run it at Jurby airfield, but I can also use it on the road over the mountain curcuit on the way back to the campsite.
This is a long stroke Manx and therefore not competative against the short strokes and parts are very hard to get for the double knocker engines, so racing would be very expensive and pointless. As Stu Rogers said to me "It's the forgotten engine". You can get everything for the SOHC engine (Inter type) and new engines for the short stroke DOHC's, but nothing for the DOHC long strokes apart from a few interchangable or adaptable parts. At the I.O.M. GP this year I saw a few short stroke Manx's blown up back at the pits, and that's with new engines fitted. So I would say I was appreciating the bike for what it is, without thrashing it to destruction, and without putting it in a glass case.
There are 2 types of DOHC Manx engine, the earlier engine I think was about 1949 which was similar to an Inter botton end with a DOHC top end and a plunger frame. The later engine was about 51-53 in the Featherbed frame and had a similar bottom end to the short stroke. The short strokes came out in 1954.
Here's a picture from the 1950 Norton cataloque showing the plunger Manx with DOHC, but notice the rev drive coming from the mag cover. You can see the similarity to the Inter above it.
The 51-53 DOHC engine looks quite different. The rev drive now comes off the left side of the head and the mag chain case is a different shape with 5 screws holding it. As far as I know, the wide finned barrels were for the works bikes and the waisted finned barrels were for bike available to privateers. I could be wrong, but I'm sure that's what I've read. This picture's of a 1953 DOHC long stroke with works barrels like mine.
Here's a picture of 1952 waisted barrel engine. Restored by Ken McIntosh