Can anyone help me identify this camshaft that I pulled out of a crossflow years ago? It is marked (crudely) BCF2. I can't upload a photo unfortunately, I wish I could.

The reason I am querying whether it is a genuine BCF2 is that the cam lift measurements don't correspond to the 6.62mm cam lift specified in the Kent Cams catalogue.

The numbers I get using a decent vernier, but with an inexpert hand are (all in mm):

6.27
6.30
6.31
6.24
6.25
6.27
6.23
6.15

[I got these numbers by taking the lobe to base circle distance and deducted the base circle.]

And the lobes don't look worn to me.

Have I got rogue cam?

Or does BCF2 indicate the profile more than the specific lift? It doesn't sound plausible to me.

Haas the BCF2 changed over time?

Am I missing something obvious? Or have I made some elementary error?

Any help appreciated.

Are the rockers 1:1? No experience but mechanical advantage might be part of the equation?

[Edited on 8/12/20 by Bluemoon]

Cam lift is not affected by rocker ratio.

Valve lift is. Valve lift is also influenced by clearance which is why Kent quote one figure for both inlet and exhaust cam lift, but different figures for valve lift as the clearance is different between inlet and exhaust.

quote:

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Originally posted by JMW
Cam lift is not affected by rocker ratio.

Valve lift is. Valve lift is also influenced by clearance which is why Kent quote one figure for both inlet and exhaust cam lift, but different figures for valve lift as the clearance is different between inlet and exhaust.

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Could it depend on how the cam is ground in the first place, so each lobe may be slightly different diameters so the cam lobe is then ground to suit the top height?

Jason

I think the standard rocker ratio is 1.54:1. Using your measured data ties up with the valve lift on the Kent cams website. I wonder if the cam lift is a typo. Might be worth giving them a call

If, i am reading this correctly, then the cam size has nothing to do with cam lift, as when the cam on a crossfliow hits the valve head, as long as the gap between the valve head, and the cam, is a constent in either exhaust 15 thou or inlet 13 thou , then the "lift"! will always be the same, assuming all the clearances were the same.

Im sorry to say, and ive built many many Xflows, but the tolerances on a Xflow. are not rocket science and you can swap bits from many many engines, and ive done so, and would never detect a problem, its only when your pushing around 150 Bhp from a 1700 does this come in to play

We are talking about an engine, that was designed in the late 1950's (pre crossflow but same bottom end) its an extremely basic engine for use today

steve