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fireant911 fireant911 is offline
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Join Date: Dec 2003
Location: Huntsville, AL
Posts: 735
Porsche Crest Distributor Vacuum Readings on 911SC

Could someone help me out with the proper vacuum readings on a 1981 911SC. I connected (spliced in-line) a vacuum gauge to the retard vacuum line on the distributor and the reading was 17 in @ 950 rpm idle. When the rpms were raised the vacuum dropped to atmospheric pressure. I rationalized with that outcome that I should see 0 in vacuum on the advance vacuum line @ idle and some 'higher' vacuum at increased rpms. I tested this and saw 0 vacuum at idle and @ 2,000 rpm I was only seeing a slight vacuum (maybe 1 in). Are these readings correct / do I need to increase the rpms to see an increase on the advance vacuum line / do I have any idea of what I am doing?
I did properly (I think) test the vacuum by tying into the vacuum port adjacent to the idle adjustment screw and recorded 17 in at idle and approximately 20 in at 2,000 rpms - though this question directly relates to the vacuum readings on the retard and advance lines at .
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Daryl G.
1981 911 SC - sold 06/29/12
Old 01-01-2004, 10:26 AM
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