Norris Cam and Regrind Questions

comnoz · Sep 14, 2019

And here are two Norton cams that give exactly the same motion at the valve.
The left is made for 7/8th radius Triumph follower and the right is for a flat Norton follower.

comnoz · Sep 14, 2019

Ron L said:
I have a 2S in my '74 850 Interstate that is otherwise stock. Runs fine, good freeway power with a 22 tooth gearbox sprocket. A little sluggish at low rpm compared to my 19 tooth 750's, but quite tolerable.

If you want to liven up the lower end when using a 2s cam on a low compression motor then re-mesh the cam gears to advance the cam 5 degrees. [or more]
It helps get back some of that grunt you lost between 3 and 5000 rpm.

o0norton0o · Sep 14, 2019

comnoz said:
And here are two Norton cams that give exactly the same motion at the valve.
The left is made for 7/8th radius Triumph follower and the right is for a flat Norton follower.

Given that the 2 cams transmit the same motion to their valve train, does either cam/follower set up wear significantly better than the other? ... and if so why... (yeah, I got questions...)

comnoz · Sep 14, 2019

o0norton0o said:
Given that the 2 cams transmit the same motion to their valve train, does either cam/follower set up wear significantly better than the other? ... and if so why... (yeah, I got questions...)

No, they seem to wear the same. This is a relatively mild street grind.

If it was a big race cam like a Norris D grind or bigger then there may be a wear advantage due to the lighter Triumph follower.

jseng1 · Sep 15, 2019

o0norton0o said:
Given that the 2 cams transmit the same motion to their valve train, does either cam/follower set up wear significantly better than the other? ... and if so why... (yeah, I got questions...)

Axtell#3 cams didn't have a lot of lift and they were available for flat lifters as well as radiused lifters. Some racers tried them both. A flat lifter Axtell cam looked beat up after a season. A radius lifter cam with the same valve action looked better with less wear. You had the choice of a pointy nose cam shape wearing on a flat surface lifter or a roundish nose cam wearing against a roundish lifter.

Matchless · Sep 15, 2019

comnoz said:
If you want to liven up the lower end when using a 2s cam on a low compression motor then re-mesh the cam gears to advance the cam 5 degrees. [or more]
It helps get back some of that grunt you lost between 3 and 5000 rpm.

Jim ,
Could the same thing work for a Maney cam which I believe is more or less the same as a 4S ?

Martyn.

comnoz · Sep 15, 2019

Matchless said:
Jim ,
Could the same thing work for a Maney cam which I believe is more or less the same as a 4S ?

Martyn.

Actually the Maney cam is a 2s combat cam. It will help to advance it with low compression.

Matchless · Sep 15, 2019

Thanks Jim, I'll give it a go on my 750 which I have always found a bit lacking at lower revs. Steve insisted that there was no need to alter it from the standard setting. The engine has a stage 1 head job & the CR is 8.7 : 1 if I remember correctly.

Ron L · Sep 15, 2019

gortnipper said:
Well, that sluggishness has nothing to do with the 2s cam.

Agreed. More a function of the 22 tooth gear vs. the 19 tooth.

swooshdave · Sep 15, 2019

comnoz said:
If you want to liven up the lower end when using a 2s cam on a low compression motor then re-mesh the cam gears to advance the cam 5 degrees. [or more]
It helps get back some of that grunt you lost between 3 and 5000 rpm.

So 9 links instead of 10?

comnoz · Sep 15, 2019

swooshdave said:
So 9 links instead of 10?

No, you would go 11 links and then go forward 3 teeth between the crank and intermediate.
1 chain tooth is 15 degrees and three gear teeth is 17.5 degrees. So that gives you 2.5 cam degrees or 5 crank degrees of advance.

Norris Cam and Regrind Questions

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