Cam info needed, please

Goofing with the cam that came out of the '74 850 engine, and a spare I have on the shelf; I need to find out which is the better cam, they are definitely different.

"Cam A", the one with more rounded lobes, has a smaller base circle (0.880") and more lift - (0.330"), it's stamped with an "S", and then appears to be hand-scribed with a second "S". It has the tang slots and shouldered drillings for the timed breather. I sure don't believe it's a "2S" cam, unless it's a re-grind with a field-applied second "S".

"Cam B" the one with the more "pointy" lobes, has a larger base circle (0.900") and less lift - (0.315"), it has no stampings whatsoever, and is from the 850 engine.

(The above cam dimensions are rough, taken with a good caliper, not a micrometer)

Can anyone shed any light on which would be the better cam to use on the 850 +.020 with stock carbs & 2-into-1 header?







Thanx for the help, guys 'n gals.

hi gp,from the cam comparisons iv,e seen the 2s has 0.390 lift on the inlets and 0.346 on the exausts, the std cam has 0.330 on both inlet and exaust

NOC camshaft info.: http://nortonownersclub.org/technical/c ... etail.html

I re-checked lobe-by-lobe and determined the cam that came out of the 850 is stock.

Now, the "SS" (2S?) cam has more lift on the intake lobes than the exhaust, so is definitely NOT stock. MIGHT be a Combat cam, MIGHT be a Megacycle 560-SS / re-grind.

Next, I need to see if I can determine the timing events, then compare it to the chart that LAB linked to.

Either way, I'm going with the S/S cam IF I can verify that it will co-exist with the flat-top pistons. I'll send the cam followers to Megacycle for radius grinding if it all works out.

I'd agree that the fact someone has scribed a second "S" would indicate it was reground with a similar characteristics. I'm just wondering if this was a pull from an engine, did it have radiused followers installed. Also it was common practice to do a little porting and polishing along with the cam, mostly on the exhaust ports. The profile would suggest it may have had larger intake valves.

I don't even remember where I got this cam; I've made trades of trades over the years.

I for sure have never had a set of radiused followers in my hands.

hi gp,if cam A is a 2s or megacycle equivalent i think you will need valve pockets in the pistons,also you may need to enlarge the cam tunnel in the crankcases,also the 2s does,nt need radius followers, hope this helps

Chris-

Yep, I'm checking all of that out. Thanx.