Atlas vs Commando Lifters

I plan on using an Atlas barrel on my 1972 Commando.
I would like to use the lifters that were in the Atlas barrel, rather than the lifters that came out of the Commando barrel.

The Atlas and Commando lifters have flat (non-radiused) stellite pads and a chamfer on the long vertical edges.

The only difference is the Atlas lifters have a short chamfer on the front and rear of the stellite foot.
This produces a working length (front to back) of .948 for the Atlas lifter, vs 1.078 for the Commando lifter.

Anybody know if Atlas lifters in a Commando engine can deal with a 2S cam?

They will work. I had a 2S in the Atlas motor in my P11 using the Atlas lifters (flat tappets with chamfered ends). Some work was done to the cases and a timing cover change was made to get the 2S in there, but the lifters were not modified. Chamfered lifter edges are not that close to where the cam lobes hit the lifters. No problems. I did not baby the motor.

Thanks Schwany. Very helpful. I was just getting ready to blue the contact surfaces to confirm that they would work through the full rotation of the cam lobes.
I still might do this. Having dressed the lifters square, I am curious about the resulting lateral/radial contact pattern.

found this:
"f you are reusing the original camshaft than you will reuse the commando followers and keep them matched to the same lobes..."

YukoNorton, normally you would be correct. But the lifter surfaces on both the Atlas and the Commando cylinder were compromised. Which is why I machined them flat, and honed them to a 600 grit finish. At that point I could use either, and theoretically it didn't matter what lobe they went back on. Initially I decided that it wqw preferable to keep the Atlas lifters in the Atlas cylinders, just because they had bedded in to that location. I was curious about width of the Atlas lifter faces with the 2S cam, because a higher lift lobe uses more surface on the lifter.

Schwany's advice was that he had no problem using the Atlas lifters with a 2S cam. Because I had machined the lifters and was using them with a used cam, I was curious about the resulting contact pattern. Using prussian blue, I was able to confirm good contact, as in the lifter was hitting the cam squarely. However with the narrower Atlas lifters, the cam lobes were making contact very close to the front and back edge of the lifter. Close enough that I could not tell if this was going to be a problem. Since I had a set of refinished Commando lifters available with a larger surface area, I used those, and built in a .0625 safety margin on the front and back side of the lifter.

I just looked at my old tappets. The SS cam gets very close, but does not hit the chamfered surface of the Atlas tappets in Atlas barrels on top of a set of Atlas cases. Can't be that much difference as far as where the cam is positioned in the Commando cases. I would have had serious problems if the cam was hitting those poorly machines chamfers. I had no problems doing it. Cam was new. The tappets were resurfaced.

Rabers or I did grind some of the arc on the bottom of the tappet bores to get added clearance for the SS cam. It was one of those safety measure things. The cam I am referring to as a 2S has an SS stamped on it. Not sure if that makes much difference.



More useless off topic and out of bounds thoughts: If Atlas pushrods are actually shorter than Commando pushrods, it would be an opportunity to use stellite caps on top of the valves if the geometry worked out for you or your trusted advisors. In my experience the stellite caps wear better than KW stellite tipped valve stems. I've never had a stellite cap break, but I suppose anything is possible. I don't know whether or not Norton engine building experts would ever use a stellite cap on a valve tip. I suppose it would depend on who they get their motor building advice from, or what they have actually tried and found worked.

I have just acquired a cam with very similar SS marking. Is it the standard Commando cam or a 2S?

jan nelder said:

I have just acquired a cam with very similar SS marking. Is it the standard Commando cam or a 2S?

Click to expand...

"The camshaft on a combat is stamped with SS, this is called a 2S camshaft and not actually an SS camshaft (the SS camshaft is actually stamped X1 or X2 - this is a point of much confusion)."

Also confirmed on dynodaves camshaft profile survey:

“ 063536 The famous or "infamous" 2S combat cam. Note*** this is MARKED "SS" on the camshaft, but it is not the 650SS (1S) grind”.

I've never seen the SS stamped on a lobe, just on the shaft near the oil slinger. Looks like an aftermarket camshaft.
A 650 camshaft wouldn't have a tach drive worm gear on it, so I wouldn't mistake it for a Combat 2S cam.
Seems straightforward, am I missing something?

I have run lash caps on a Commando with a stock cam with no troubles. I currently have a 2S cam but can't remember if I ever used lash caps on it. The 2S cam sacrifices bottom end but yielded significantly better gas mileage than the stock cam. I personally like the stock Atlas cam in my 750 Atlas best.

For anyone that enjoys going off topic even more, the JS2SS cam has all that SS top end and more torque down low. It is a very nice street cam for crazy guys like myself. Not sure if anyone else would ever agree, but I am not caring. I'm running lash caps on the KW valves being pushed down by the JS2SS and pushed up by the JSM springs. Fun motor.

Deckard said:

I've never seen the SS stamped on a lobe, just on the shaft near the oil slinger. Looks like an aftermarket camshaft.
A 650 camshaft wouldn't have a tach drive worm gear on it, so I wouldn't mistake it for a Combat 2S cam.
Seems straightforward, am I missing something?

Click to expand...

My Norton history knowledge is very limited. My BS supply is endless.

What I know is the cam I posted a pic of is a SS cam for a Commando and it supports an AAU or IE at the timing side and no timed breather machine work on the drive side. I'd never heard of a Combat Commando when I got the cam. Too many other toys to really care that much. The case modifications I mentioned basically turned my P11 Atlas engine into a tweener Atlas that uses Commando cams. My engine has an early Commando timing cover on it. The SS cam was purchased new from Bob Raber of Raber's Parts Mart in San Jose CA. He was still in the old Brook's building at the time. I don't really have a clue where he got it. His people did the work in the P11 cases to support Commando cams. The SS marked cam, be it aftermarket or not, has more lift than the JS2SS cam I replaced it with. The SS cam was a little more on the violent side because it lacked some torque at the bottom end. The JS2SS has a linear feel to it, but still gets to getting it on top.

I did not ask Bob for a SS cam. All I told him is I wanted to make my P11 engine a little quicker. He chose the cam, and said it'll require a few changes to the engine.

Schwany, your comment earlier: "Rabers or I did grind some of the arc on the bottom of the tappet bores to get added clearance for the SS cam." is important.

I noticed the camshaft was trying to lift the barrel as it rotated. The cam was bumping the bottom of the tapper bores. I had to regrind the bottom of the tapper bores, as per the Commando barrel I was using previously, to get the clearance for the larger sweep of the 2S cam.

Schwany said:

My Norton history knowledge is very limited. My BS supply is endless.

Click to expand...

That describes a good few of us...