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| | | | Joined: Dec 2021 Posts: 20 'Bolter | | 'Bolter Joined: Dec 2021 Posts: 20 | Hey again everyone! so this time we have a question about the carburetor on our GMC 5500, for those new we are working on a 1972 GMC 5500 with a 350 V8 engine inside of it. Person we got it from had given a new carb with it and while reading one of the manuals we bought for working on it we learned about the distributor advance/speed governer thing and swithced the vacuum lines to run that we think properly which gave us a better idle. but now we have like, 3 vacuum lines total for the carb and many ports closed off. anyone have any diagrams or anything that might be able to help us with this? | | | | | Joined: May 2005 Posts: 8,983 Sir Searchalot | | Sir Searchalot Joined: May 2005 Posts: 8,983 | Sure would be nice to know what carb it is. There should be a special port for your vacuum advance which has low or no vacuum at idle. This is above the throttle places. It will be a small nipple. The others can be for PCV, brake booster, automatic kick down, wipers......... Some of those can be on the manifold.
If you don't have a use for anything but vacuum advance, you cap the rest.
Manifold vacuum and carb base (below throttle plates) vacuum is the same.
There will be a vacuum diagram for your truck somewhere on the web or a member here will have a manual. Seems like your "manual" should identify each port???? The one for the distributor is called "timed".
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn
| | | | | Joined: Dec 2021 Posts: 20 'Bolter | | 'Bolter Joined: Dec 2021 Posts: 20 | The one for the distributor is actually just labled as "Distributor Vacuum" plus as I said, a non-original carb was put onto it which has WAAAY more then it needs to have. As far as I can tell, we have one line that goes into a diaphram for the advance, one for a missing "TSC" system, and one for the PCV valve. Windshild wipers are not vacuum powered on this truck, and Im also having to use the 1970's manual since 1972 does NOT have a manual for my truck. | | | | | Joined: May 2005 Posts: 8,983 Sir Searchalot | | Sir Searchalot Joined: May 2005 Posts: 8,983 | I guess you've answered the question? 
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn
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