valve clearence , B motor

[[email protected]]

I am building a B motor with modern valves, stock B cam, high compression head , down draft carb 81. What should the valves be set to ?

[ursus]

Have you measured the lift on all of the lobes on the B-cam?

[[email protected]]

brand new cam never been used

[mcgarrett]

I don't know if it applies to "B" cams, but Les Andrews' book calls for .013" for intake valves and .015" for exhaust ford Model A cams. Maybe others here on the Barn will chime in.

[Big hammer]

I think on the ford garage site there’s a chart for valve clearances with different cams

[ursus]

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Originally Posted by [email protected]

brand new cam never been used

A new NOS Ford Model B cam or some other interpretation thereof? The stock Model B cam had an intake lobe lift of 0.334 inches (0.015 inch valve clearance) and an exhaust lobe lift of 0.341 inches (0.022 inch valve clearance. Reground B cams can come in a variety of specs.

What does the maker of the cam recommend?

[Benson]

Also the stock NOS Model B camshaft (un-reground cam) used a unique lifter (lifter is longer and heel is larger in diameter) which if used with the smaller diameter model A lifter will result in damage to both the camshaft and the lifter.

[Jim Brierley]

Originally Posted by ursus

A new NOS Ford Model B cam or some other interpretation thereof? The stock Model B cam had an intake lobe lift of 0.334 inches (0.015 inch valve clearance) and an exhaust lobe lift of 0.341 inches (0.022 inch valve clearance. Reground B cams can come in a variety of specs.

What does the maker of the cam recommend?

There were 3 different B grinds, the most common one had .302" lift, the next one had .315" and the latest one had .339" an slightly more duration than the others.

[nkaminar]

Valve clearance has to do with how things change with temperature and how the cam was ground. Some have a ramp that closes up the gap so that the tappet noise is reduced, and some don't. I would start with the Model A clearances and then measure the gap as the cam comes up on the lift part. If the gap gets smaller as the cam approaches the lifting part, then there is a ramp and you may want to increase the gap. If the tappets are really noisy than you may want to reduce the gap.