Crane adjustable vacuum advance

40cpe

40cpe

Well-known member
Can anyone tell me what the advance range is on the Crane advance? I haven't bee able to find it with searches. I'm trying to get my static advance up and stay within tolerance on the total advance. My current advance is adjustable, but I can't get it below 13-14 degrees.
 
The Ford distributor vacuum pot adjustment screws (down inside the vacuum port) must vary in their total travel???? May be but I have set many down as far as 5º-7º or so. It turns CCW to reduce travel - opposite the intuitive "screw it in" tendency we all have.

I've got one hanging around that won't adjust (screw turns freely) because the threads must be stripped. Many old originals have rust down in the mechanism and the frozen threads strip easily.

 
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The one I have is like the one pictured. It feels like it has backed out of the threads. Thanks for all your help.

Gene
 
The adjusting screw on the vacuum unit appears to be working, I just have it backed all the way to minimum advance. Do the springs in the mechanical advance have any effect on the vacuum advance? I have them set for all in about 2500 rpm.

I called Crane and they don't have any specs on the adjustment range of their advance unit. The tech said the springs in their kit are to help adjust the vacuum advance. It appears to me that the vacuum plate moves independent of the centrifugal advance.

Thanks for any education you can give me.
 
I don't have any idea about your compression ratio or expected state of tune so ......for a four barrel stocker. Try 10 - 12 degrees initial crank advance, limit the distributor mechanical advance to 12 to 13 degrees (additional 24 to 26 at the crank) for a total of 34 to 38. That is with no vacuum advance at all - hose sealed at the carb and open at the vac pot. At idle, tuned for max vacuum, apply manifold vacuum to the distributor and take a look at how much the timing advances. To take a stab at it, try to adjust for 10 degrees vac advance and take a drive. Avoid getting so much early mechanical advance that she knocks. Learning how to set it up in the drive is an old tradition - have fun.
 
Thanks Greenbird. I've been playing with this combination for a while now. I bought the Crane adjustable vacuum can/springs and it will only adjust to a minimum of 12 degrees advance at the crank. I then bought a remanned distributor with an adjustable unit on it and it only adjusts to a minimum of about 16 degrees advance. All of these advances will turn CCW until I can feel them run out of threads and hear the "click" as the last thread disengages.

With this distributor set for the 26 degree mechanical advance and 10 degrees initial, the engine has about 55 degrees advance all in at about 3200 RPM. I have installed a timing tape for my size balancer, so the reading should be fairly accurate. The engine seems to run good with no knocking/pinging at any speed that I can hear. I realize that the engine probably isn't making full vacuum on the road under load, thus reducing the advance some from what I see in the garage. My concern is about the total I'm seeing. Most articles I read say to limit the total of initial, mechanical, and vacuum to about 45 degrees. Am I in danger of hurting my engine with the total I have?

Thanks for any comments/experience from all.

Gene
 
Ideally 38 degrees is the maximum total advance that Ford recommended. I would guess that if you are getting a total of 45 degrees that the engine could be miss firing if you brought the throttle up over 3000 rpms (or wherever max advance comes in) and held it there. Connect a vac gauge to manifold vac and make the test yourself at 3K, then slowly retard the distributor and see if the vac increases or decreases. Better yet connect to an infra red and watch the hydrocarbons
 
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