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1985 vacum break queston

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Aug 12, 2012, 9:58 AM

Post #1 of 2 (1882 views)
1985 vacum break queston Sign In

I have an 1985 gmc c/2500 pickup with a 350 ci engine and a four barrel carb. there is a vacum line on the vacume break secondary side, but there is a place on the back for what looks like another vacum line. it is on the back side closest to the firewall. should there be a vacum line there and if so, where should it go.

Tom Greenleaf
Ultimate Carjunky / Moderator
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Aug 12, 2012, 11:28 AM

Post #2 of 2 (1866 views)
Re: 1985 vacuum break question Sign In

Primary choke pull off (that's what they are) is the front most diaphragm and most important. It should get instant manifold vacuum. Second one should be routed from a thermal switch in the metal of air filter housing when warmed a bit inside will open choke a bit more than the first. Specs for Primary and Secondary is what you want to set those.

It doesn't take too long if choke warms up on time for neither to be doing anything but going along for the ride. Without the primary working at all carb will flood out fairly easily,


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