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68gmsee · 11-07-2008, 11:46 AM

It seems like you have some sort of smog/emissions control stuff on your truck that is not installed on other trucks like mine. I believe it"s called a "Thermac" system. It's also possible someone changed things around on you. Maybe somenone from the west coast has more info.

I have a plain vanilla six on my 68 and as you mentioned, the pvc valve goes to a fitting on the intake manifold next to the carburetor. The vacuum advance goes to a fitting on the carb that's on the passenger side of the carb next to the pvc fitting. This is ported vacuum. There should be another vacuum on your carb lower than that one that's engine vacuum. I've used both but prefer the ported vacuum on this truck. Any other open vacuum ports should be capped off.

If you need it, I can take a picture of mine later on today to give you an idea.

11-07-2008, 11:46 AM	#2
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Need Help 70 250 vaccum hose route? It seems like you have some sort of smog/emissions control stuff on your truck that is not installed on other trucks like mine. I believe it"s called a "Thermac" system. It's also possible someone changed things around on you. Maybe somenone from the west coast has more info. I have a plain vanilla six on my 68 and as you mentioned, the pvc valve goes to a fitting on the intake manifold next to the carburetor. The vacuum advance goes to a fitting on the carb that's on the passenger side of the carb next to the pvc fitting. This is ported vacuum. There should be another vacuum on your carb lower than that one that's engine vacuum. I've used both but prefer the ported vacuum on this truck. Any other open vacuum ports should be capped off. If you need it, I can take a picture of mine later on today to give you an idea.