Q: Camshaft marking?

Ladies and gents,

I found a camshaft with the making "R" in one of my "Rotten Commandos", am I correct that this is actually an 2S grind?


Tim

Tintin,
Thanks for starting this thread. I can't answer your question, but have a similar question about cams; I suspect that the amswer to your question will also supply an answer to my question, so I'll include my question as well, not tryimg to hijack your thread:

I have a '72 750 which has a "C" stamped on the head, was fitted with 932 Amals, had a deck height of +1mm and was fitted with a cam that has two markings, A "v", "y" or "x" and SS. I assume that I have a Combat and there is evidence that someone was inside the engine, at one point; both mains are SuperBlends, and the engine has 18K+ miles on it, which lead me to believe that something was changed; I thought that I should have found a SSSS (4S?) cam; what do you folks think?

RS

Sorry I can't answer either of the previous questions,

If it's any help my Mk3 cam was marked "P" which stands for "Piss Poor"

Graeme.

RoadScholar said:

I have a '72 750 which has a "C" stamped on the head, was fitted with 932 Amals, had a deck height of +1mm and was fitted with a cam that has two markings, A "v", "y" or "x" and SS.

Click to expand...

My engine definetly is not a Combat but heavily modified. CR must be higher than 12:1, it's the one with this head on:

commando-flathead-well-somehow-t5354.html

Carbs are 930s, ports are polished but still rather small with my vernier gauge reading at 29.whatever. The pistons are of the evil slotted "mechanical rev limiter" type and the engine has no Superblends. I strongly assume that this engine was assembled by some nitwit who slightly overdid it and when it was first started it ran like sh*t and whoever did it lost interest. There is no wear on moving parts and the oil in the engine is still clear and yellow.

From the details (1971 serial no. on the case, no Superblends and slotted pistons) I'd guess that it was either assembled before Superblends became standard (1972 IIRC) or in a region with absolutely no means of communication....;-)



Tim

Since the topic has been resurrected, and my related question was never definitively answere, I'll thow out the basis for the question again, and ask "what is it?"

It has a single "S" stamped by the manufacturer, and a second "S" scribed with an engraver.

RoadScholar said:

Tintin,
Thanks for starting this thread. I can't answer your question, but have a similar question about cams; I suspect that the amswer to your question will also supply an answer to my question, so I'll include my question as well, not tryimg to hijack your thread:

I have a '72 750 which has a "C" stamped on the head, was fitted with 932 Amals, had a deck height of +1mm and was fitted with a cam that has two markings, A "v", "y" or "x" and SS. I assume that I have a Combat and there is evidence that someone was inside the engine, at one point; both mains are SuperBlends, and the engine has 18K+ miles on it, which lead me to believe that something was changed; I thought that I should have found a SSSS (4S?) cam; what do you folks think?

RS

Click to expand...

Your 2S cam (stamped SS) is the correct original cam for the Combat. The 4S (stamped 4S) is a later profile. The only production engine that came from the factory with it intalled was the 750 short stroke, although it became a popular cam with racers for use in the conventional long-stroke engines too. FYI, the 3S (stamped SSS) cam was the same timing as the 2S, but with more lift, and the same .016" clearance spec as the 4S. It was the spec cam for the Production Racers, although it didn't get installed in all of them. Although it gave a slight horsepower increase over the 2S, it wasn't a particularly good cam, and never gained much popularity with racers.

Ken

Tintin said:

Ladies and gents,

I found a camshaft with the making "R" in one of my "Rotten Commandos", am I correct that this is actually an 2S grind?


Tim

Click to expand...

Back in the '70s, Norris had an "R" grind cam for the 750 Norton (and a D grind). It had .424" of lift at the valve, and 318 degrees duration. I'm not sure how it was marked, but that might be a possibility. As far as I know, all the Commando 2S cams were stamped either SS (early) or 2S (later).

Ken

lcrken said:

Back in the '70s, Norris had an "R" grind cam for the 750 Norton (and a D grind).

Click to expand...

Thanks, very nice info! I googled for Norris Commando and guess what I found:

megacycle-cam-install-t2393.html

I'll measure lift and duration.

If it is a Norris, how good would an early 70ies items be in terms of quality, hardness etc.?


Tim

lcrken said:

:Back in the '70s, Norris had an "R" grind cam for the 750 Norton (and a D grind). It had .424" of lift at the valve, ....

Click to expand...

:cry: No, it's not a Norris R, it's more likely a stock cam with a measured .33? lift.....on the other hand I intend to build the engine as a lazy tourer anyway....


Tim

Yep, with that sort of lift at the cam it can't be anything but a stock cam. It should be fine. The stock cam is actually pretty decent for performance. I road raced a 750 for a while with a stock cam, and it worked very well, good enough for some second place finishes back in the early '70s.

Ken

I have this cam in my 1970 Roadster, there were no markings on it, has the breather facing on the end of the cam, what is it ?.

Looks like a stock early Commando cam to me. I have a couple just like it, and they also have no markings. Unless it's been hardfaced welded and reground (hard to tell for sure from the pictures), there's no reason to believe it's anything but stock.

Ken