Distributor Vacuum Question
Thread Starter
Racer
Joined: Mar 2008
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Distributor Vacuum Question
With a 1980 HEI distributor, does the vacuum line going to the carb get connected to a ported vacuum source or is it manifold vacuum? In other words, is the connection above or below the throttle plates? My routing diagram only shows the hose going to the carb.
Melting Slicks
Joined: Nov 2001
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From: Eastern US XX
Distributor vacuum is ALWAYS "below the throttle plates" whether it is manifold or ported - which are exactly the same EXCEPT at idle. See which one the car runs best with - usually manifold is preferred, but ymmv.
Safety Car
Joined: Oct 2006
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From: Gig Harbor WA
Race Director
Joined: Jul 2004
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From: Scottsdale Arizona
There is also a good paper that Lars has written with another author his name escapes me) on choosing the right vacuum advance. Drop him a line for a copy.
Le Mans Master
Joined: Apr 2004
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From: Newark DE
http://www.lbfun.com/warehouse/tech_...ance_Specs.pdf
It's on my tech articles page under the Timing & Vacuum Advance header
Thread Starter
Racer
Joined: Mar 2008
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But, I was hoping that somebody might know how the vacuum connection originally came in 1980.
Tech Contributor
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From: At my Bar drinking and wrenching in Lafayette Colorado
Lars
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Team Owner
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From: Crossville TN
Being "above or below the throttle plates" has little to do with where the vacuum port is located on the carburetor. Internal cast & drilled passages can allow 'manifold' vacuum to be up on the side of the carb body. The easy way to figure out if a port is linked to manifold or not is to remove the hose and see if a scrap of paper will remain held by the vacuum or not [when car is idling]. If it won't stay on the end of the port, it's "ported".
Tech Contributor
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From: At my Bar drinking and wrenching in Lafayette Colorado
Lars
