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356-930 356-930 is offline
Acceleration Junkie
Join Date: Aug 2007
Location: Laguna Beach, CA
Posts: 263
Originally Posted by billjam View Post
Is there anyone out there with a vacuum unit from a 930/68 motor that they can test for me?
I would like to know what happens when you blow and suck in each of the ports.
My '79 930 distributor has a similar looking vac/boost unit. It is unlikely Porsche altered the operation of this accessory over time.
Note that it's very easy to draw almost a full vacuum by mouth, near impossible to generate even +1-psi by mouth. Get yourself a hand pump, even a bulb and rubber hose off a blood pressure cuff. Easy to generate 15-psi with a blood pressure cuff bulb.
Port A is vac. retard (vac pulls timing out of distributor). A positive pressure on port A will do nothing. Port B is boost pressure retard (positive pressure on port B also retards timing). Vacuum on port B will not affect timing.
Both ports should hold vac or pressure.
Old 08-19-2008, 05:54 PM
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