Crab vaccuum brake rubber seal

[pooch]

I dug out the remains of the seal between the crab body and the block and found it to be about 1/4 inch deep.

Obviously too deep for an O ring.

I guess the seal is like a short cut piece of rubber pipe?

[Mart]

Yes, if you can't source a genuine part, you can use a piece cut from a suitable rubber hose. I did it, it took a few tries to get one I was happy with, but it is do-able.

Mart.

[RKS.PA]

I seem to remember an earlier post by Charlieny on this topic. I needed a seal at the time, followed his advice with a piece to rubber tubing, and it worked like a charm. Can't recall the timing of the post, but it was a couple of years ago.

[philipswanson]

Why use it? All it does is slow down the advance on an already anemic advance curve.

[Mart]

It steadies the mechanism. Light drag is better than no contact. It isn't like a modern setup with return springs. there are springs but it requires the slight drag to keep it all settled.

Mart.

[pooch]

Sponsored Links (Register now to hide all advertisements)

Yep, our resident guru Bubba, says to have a slight drag on brake, so I will go with that.

[philipswanson]

OK, so how do you adjust for a slight drag? In all the way and back out how much?

[pooch]

I found it took very little suction to draw the piston back.

I doubt there would be much drag on it anyway once the engine started and even under acceleration..

Handy to have a bit of drag /retard /non advance tho, when occasionally I have to hand crank the sucker.

[BUBBAS IGNITION]

Originally Posted by philipswanson

OK, so how do you adjust for a slight drag? In all the way and back out how much?

On our rebuilds we turn all out and then in three turns for contact. Seems to work until it can be properly adjusted on the car..

[philipswanson]

OK good but how would you adjust it on the car? Is it the same for helmets?

[BUBBAS IGNITION]

Originally Posted by philipswanson

OK good but how would you adjust it on the car? Is it the same for helmets?

The Ford TSB says to clean, lube and turn three turns inward. Then drive the car and turn screw outward until slight spark knock is audible under load , turn inward until you experience no knock under slight load......
And a helmet would be the same issue.........