Atlas cam

pierodn · Oct 10, 2016

Hi.
Two questions, please:
First: what is the thread of the cam?;
Second: i have three good usable cam.
They all seems the same.
All are marked T2219 but only one is marked also X1.
Any differences?
Thank you.
Piero

Rohan · Oct 10, 2016

T2219 was just the number on the cam blank for dommie twins - for quite a long way back (late 1940s).
It doesn't seem to identify the cams in any way - other than that they are definitely Norton.

I'll leave the X1 for someone else, but have seen this mentioned as something to do with the hardening process
(as was X2 ?).
But this identifies them as Atlas era (?).

In theory, you can just measure the height of the 'bump' on the cam, and figure out which grind this makes it... (??).

pierodn · Oct 10, 2016

Rohan said:
T2219 was just the number on the cam blank for dommie twins - for quite a long way back (late 1940s).
It doesn't seem to identify the cams in any way - other than that they are definitely Norton.

I'll leave the X1 for someone else, but have seen this mentioned as something to do with the hardening process
(as was X2 ?).
But this identifies them as Atlas era (?).

In theory, you can just measure the height of the 'bump' on the cam, and figure out which grind this makes it... (??).

Hi.
The bumps measure all the same 33,5 mm.
Ciao
Piero

Mike B · Oct 10, 2016

X1 relates to hardness depth, X2 has twice the hardness, while you can consider anything without those markings to X1. (If memory serves me).
Don't what the actual depth of hardness is............no clue. The fact that the one cam is marked would indicate a more recent manufacture. (again, I think so).

Mike B.

texasSlick · Oct 10, 2016

pierodn said:
Rohan said:

In theory, you can just measure the height of the 'bump' on the cam, and figure out which grind this makes it... (??).

Click to expand...

Hi.
The bumps measure all the same 33,5 mm.
Ciao
Piero

Piero:

The base circle must be subtracted from your measurement to determine lift. Lift should be about 8.5 mm for Atlas cam.

Slick

pierodn · Oct 11, 2016

texasSlick said:
pierodn said:

Rohan said:

In theory, you can just measure the height of the 'bump' on the cam, and figure out which grind this makes it... (??).

Click to expand...

Hi.
The bumps measure all the same 33,5 mm.
Ciao
Piero

Click to expand...

Piero:

The base circle must be subtracted from your measurement to determine lift. Lift should be about 8.5 mm for Atlas cam.

Slick

Hi Slick,
the bumps measure about 8,5 mm, the same of my Commando 1970/71 cams.
Thank you.
Piero

Rohan · Oct 14, 2016

The std Commando cam is reportedly the same grind as an Atlas cam, so that would make sense...
Sounds like all 3 of your cams are the same, and Atlas then.

Do the cam lobes look like all the same shape.
This can be tough to just eyeball, some seeming slight differences can mean quite a difference...

texasSlick · Oct 15, 2016

Rohan said:
The std Commando cam is reportedly the same grind as an Atlas cam, so that would make sense...
Sounds like all 3 of your cams are the same, and Atlas then.

Do the cam lobes look like all the same shape.
This can be tough to just eyeball, some seeming slight differences can mean quite a difference...

Agree!

Only doing a degree wheel and dial indicator test can determine any differences.

Slick