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Can you put a r45 cam in a 247 engine? The reason I ask is because, as far as I know, the general cam specs of the 284 cams in the r50 and r45 are the same, except that the lift in the r45 cam are slightly higher. I use a r50 cam in my r90/6 with sidecar. The 284 cam gives a lot more torque in the lower rpm range. Generally I’m very satisfied, and I am no speed devil. But when not driving with a sidecar, the 284 can loose torque a bit early in the higher revs. I don’t want to change the final drive each time I go without sidecar.
But if the r45 284 cam could fit, and it has 0,6mm more lift, I would not really loose any low end torque, but would gain a bit more midrange torque.
I have electronic ignition on the crank, so I don’t use the “points” tip, so that would not be a problem.

No I don't believe it will work at least not while maintaining the same cam timings.

As you say type 248 R45 and R65 cams have the same basic timing as type 247 cams so the the standard 35hp R45 cam is a 308 and the 27hp R45 cam is a 284 and those 284's by the way are very rare outside of mainland Europe. But in any case the they are not the same cam as a type 247 equivalent because the shorter stroke of the type 248 changes the angle of the pushrods which changes the timing.

barryh wrote: ↑Sat Sep 13, 2025 5:53 pm But in any case the they are not the same cam as a type 247 equivalent because the shorter stroke of the type 248 changes the angle of the pushrods which changes the timing.

Absolutely right. The effect of changing the angle between the pushrod and the camshaft will move the timing for one 'engine' forward and that for the other 'backwards so that each will be out by the same amount but in opposite directions. I don't suppose this would stop the engine from running and I doubt it would cause any intereference between piston and valve (although I would want to check very carefully before I buttoned the engine up) but it would inevitably mean that the engine would run unevenly and be impossible to balance.

Rob