I was interested to read recently about someone who has a Norton 16h fitted with a Big 4 engine. I have been thinking of putting a spare Big 4 engine in a 16h and wondered if anyone has experiance of doing this? Is it simply a bolt in conversion, is it necessary to alter the frame at all, what gearing do you need and how do they perform. Any help would be welcome. Cheers John
John I had a 16H with a Big 4 engine here last year. I never had it running. It's a straight forward fit though. I'd say it would be best to raise the gearing from standard 16H. It would certainly pull a much higher gear. Maybe check out the spec on a post war B4. (600cc)
Bram had the engine and Horror had most of the rest for his Model 18 replica.
I believe that the only period Norton sv / Ohv engine which won't fit in the high ground clearance WD16H frame is the OHV 600cc Model 19.
If fitted with the WD16H flat-bottomed fuel tank, spark plug access will be extremely tight. A pre-war civilian tank with OHV cutaways or indeed the WD Big 4 tank would make life easier.
You'll also need the 1938 pattern magneto platform (as per SWD Big4)with the greater timing side overhang than the WD16H type.
The 120mm stroke Big 4 engine is not really a revver. It was always sold and nearly always used as a sidecar tug. The big advantage will be torque rather than top speed.
Pre-war civilian 16H and Big 4 always shared the same gearing. If running a 43t WD rear drum, you could probably safely go up to a 20t engine sprocket (WD 18t / civilian 19t).
