Camshafts in housings - how much resistance?

[Jonny042]

Hello all,

When checking the fit of my new cams in the bare housings there is a slight resistance to them turning. I can turn them by grabbing the snout with my fingers and thumb and giving it a twist, but there is slight friction, and the cam doesn't "spin" freely in the housing due to some slight drag.

If I had to guess I'd say there is 1/4 foot-pounds of torque required to get them to spin. It's very slight, but is accompanied by a bit of a rubbing noise.

I'm telling myself that obviously the cam journals aren't subjected to the huge loads a conrod big end or crank sees, that it spins at half the speed, and that the old cams fit/turn/feel the same.

I did a very quick check of the oil clearance and it's in the .0025" range. Pretty much what you'd expect.

Maybe the result of a few nicks in the bare aluminum bores from taking the cams in and out?

EDIT/PS - I did try the cams in the housings on the bench before bolting them to the motor. No difference when installed/torqued to the heads.

[dannobee]

Were the cam journals were oiled on installation?

Use v-blocks and a dial indicator to measure the runout on the cams to see if they're straight.

[mike sampsel]

FWIW:

I decided if I could turn my cam easily with a finger and gimpy thumb I was good. Cams were lubed with assembly lube prior to insertion. There is still some friction with the lube and inertia with the cam mass, it won’t be a perpetual motion machine once you move it. I could hear a bit of noise too if I recall correctly, the joy of cam journals with 115k miles I expect.

If you have new cams, I suspect they are straight.

[Bigtoe32067]

If you can turn them all the around with your fingers then you’re good
Tony

[Jonny042]

Originally Posted by mike sampsel

FWIW:

I decided if I could turn my cam easily with a finger and gimpy thumb I was good. Cams were lubed with assembly lube prior to insertion. There is still some friction with the lube and inertia with the cam mass, it won’t be a perpetual motion machine once you move it. I could hear a bit of noise too if I recall correctly, the joy of cam journals with 115k miles I expect.

If you have new cams, I suspect they are straight.

Haha I'm using my gimpy thumb too! My physiotherapist measures the strength and says I'm at least 100% of my left hand but it's still limited in certain directions.

[Flat6pac]

Once you start with oil pressure and flow the resistance becomes insignificant
Bruce