cam timing std cam in a 70 750 using measured lift @TDC on the inlet pushrod

watson rider said:

why early Commando.s went better than later (inc C0mbats) has more to do witn cylinder heads than any thing else,check out the port sizes and shaping.this was explained to me directly by a ex factory road tester,recounting his days riding his own early green Fastback,regards Watson Rider

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I'd have to see the lobe centers of the Combat cam and the early model bikes they testers ran. I have only a few experiences with lobe center on both models cams and would have to see many examples to be sure. But for drag racing purposes you can take any cam and make it suck in the 1/4 mile with crappy lobe centers like my Combat had. The lobe centers were off approx 8-10 degrees of what I believe earlier models had. How they took a high lift cam and higher compression and decent shaped ports( for the time) and 32mm carbs slower ( if that holds up for a large sampling) was strange. But I've heard some guys back in the day with Combats say some real fast times, they did., What was done to them I don't know. Rider skill and track conditions and tuning as well as engine freshness and how they are broken in, play a huge part too.

Off the same assembly line, some bikes have it and some bikes don't. I know my cam builders WEB and Norris gave me good LCs for bottom end and acceleration and it showed at the track.

watson rider said:

why early Commando.s went better than later (inc C0mbats) has more to do witn cylinder heads than any thing else,check out the port sizes and shaping.this was explained to me directly by a ex factory road tester,recounting his days riding his own early green Fastback,regards Watson Rider

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The easy fix for Combat heads is the new raised intake (and exhaust) port floors. Increased velocity and flow.

jseng1 said:

The easy fix for Combat heads is the new raised intake (and exhaust) port floors. Increased velocity and flow.

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I do not know why I did not think of doing that. The whole thing is about resonance at around TDC. I was very careful to make sure the pipe was very smooth internally where it fits to the head - no ridges or steps. If I am ever going to ride my bike again, I will buy those.
In the old days, we made a lot of assumptions based on what was already being raced - megaphone exhausts looked good, but they were really bad - same with big inlet ports, I actually ported a Triumph head bigger when I was seeking more torque.