The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - Opinions needed, change the ignition timing?

**swervin ervin** · 06-23-2003, 09:35 PM

I don't know why everyone thinks GM always ran the vacuum advance on a ported source. It just ain't true.

Even when my truck had the 305, it was hooked to full manifold vacuum, throught the TVS. Full manifold vacuum is the preferred place to hook it too. Never heard of any off idle miss because of it. Only reason you would ever want to run ported vacuum advance is because the distributor refuses to work with manifold vacuum. This is because it's not set up right in the first place.

A properly setup distributor will work wonders with mileage and power. Don't just limit vacuum advance, do the whole nine yards.

Check this article for some good advice.

06-23-2003, 09:35 PM	#8
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	I don't know why everyone thinks GM always ran the vacuum advance on a ported source. It just ain't true. Even when my truck had the 305, it was hooked to full manifold vacuum, throught the TVS. Full manifold vacuum is the preferred place to hook it too. Never heard of any off idle miss because of it. Only reason you would ever want to run ported vacuum advance is because the distributor refuses to work with manifold vacuum. This is because it's not set up right in the first place. A properly setup distributor will work wonders with mileage and power. Don't just limit vacuum advance, do the whole nine yards. Check this article for some good advice.