The double S (combat) cam will go into any Commando engine. The bearing surface of this cam is smooth rather than scrolled, so the scrolled cam bushes are use instead of smooth. You may have to increase compression ratio to get the best performance. If you're using standard pistons you should not have any clearance problems. I don't think you can get "PowerMax" domed pistons anymore.
The double S cam isn't the only solution to increased output. You may want to research some of the profiles from Norvil Motorcycles (England) or other sources.
Just a note on cams for norton commandos, I installed a combat cam in my MKIII and found that I had to grind away on the crankcase area to allow the larger lobes to clear everything.
Also a combat cam in any 850 REQUIRES cutting valve relief notches in the pistons(like the 750 pistons have. If you cut the head to raise the compression, shorten the pushrods by the SAME ammount it maintain correct rocker geometry.
Actually the rocker arm ratio is 1.1:1 so the pushrods should be reduced in length by 45 thousandths of an inch to compensate for 40 thousandths removed from the head for the "C" 750 head. Norton neglected to do that on the combat engines. I tried freezing my pushrods to see if the steel ends would come off, but no luck. Anyone got an idea?
The mods discussed above are covered (text and graphics) in the "stage 1 850 tuning" document. It is Service Release N3/73.
For shorter pushrods, I would just buy a $40 set of Smith Bros cro-moly pushrods. I could elaborate on the reasons, but won't - except to say that Smith's are the weapon of choice for Keith Johnson's Brit motored AHRMA flat-track and roadrace motors.
Tell Smith Bros you're looking for the shorter set he makes for Keith Johnson of Johnson Cams.
Thanks, that helps me a lot. I didn't go with shorter pushrods on the combat during the restoration 8 years ago because is was a hassle finding them. The head's off now getting an oversized left exhaust guide that came loose. Good timing.
I ordered the pushrods. Guess we had a failure to communicate. I asked for a set, they sent two (one intake one exhaust). Actually it's probably better. I asked for the short ones as you suggested and they are exactly the same length as originals that came with my combat. Being heavier than the alloy stock pushrods is a also bad thing. For now I'll stay with the stock jobs.
In a previous string you posted a picture of (Like my lightened polished rockers with swivelfoot Porshe adjusters?) Do you feel the Porsche adjusters are better than a mushroom head adjuster? What's the advantage? I assume the Porsche parts have metric threads, how did you modify the rockers for this?