Distributor can vacuum source

[Steve D.]

The link below is to photos of a Holley 4160 carburetor showing the vacuum take-offs. Could someone tell me which one(or ones)would qualify as a "full time" source as opposed to a "ported source?

Steve




Vacuum take-offs

[Duke W.]

Re: Distributor can vacuum source

I could not expand the photos, but since I'm not a Holley guru, it probably doesnt make any difference.

If you don't get an definitive answer, test all the available ports with your vacuum gage. I would expect at least one to be full manifold vacuum, but you never know. If it has an external chock vacuum break line, that will work. You can tee into it.

The other alternative is to use a source directly from the manifold is one is available.

Duke

[G B.]

Odd duck

That 4160 has a large atmospheric vent(?) hose connection on the passenger side of the primary fuel bowl. Weird. That connection has no vacuum. It should be plumbed to the smog system charcoal canister, assuming your car has one.

The large hose connection in the baseplate near the rear on the passenger side should have a hose routed to the PCV valve. This connection has full-time vacuum.

The two small hose connections in the baseplate near the passenger side front corner are probably full-time vacuum sources. One tiny hose is normally routed from one of these connections to a vacuum choke pull-off diaphragm (which your carb doesn't have). The other small connector is usually routed to the distributor vacuum advance if it's full-time.

The medium sized hose connection located half-way up the passenger side of the primary metering block is a ported vacuum source. It would be connected to the distributor vacuum advance canister if your car was one of those communist smog control late madels made after 1967.

[Craig S.]

Re: Odd duck

Jerry - looks like the baseplate on my 3814 (67 A.I.R.) L79. I think the 3810's had the port plumbed out the back.....Craig

[Craig S.]

Re: Odd duck

However, the electric choke is not correct......should be divorced choke to manifold.....Craig

[Steve D.]

Thanks. *NM*

[G B.]

A much later carb

Craig, Steve's carb isn't a stock Corvette Holley, and I'm sure he's aware of that. That large hose connection on the top of his primary bowl is to capture gas vapors from the bowl vent. That was a feature found only on much later Holleys.

Also, I believe you have two large hose connections in your 3814 baseplate: a huge one for the smog pump by-pass hose as well as a 3/8" connection for the PCV valve hose. Right?

[Craig S.]

Re: A much later carb

Jerry - Yep, you are right........I was "snoozing" when I looked at that picture! And my brain must have been off. The large opening in the baseplate is on the passenger side of the plate in the rear, near the location in Steves picture of the fitting with the rubber nipple. The PCV fitting on my 3814 is in the back if I recall. I guess the 3810 had the PCV in the same location I have the large opening for the smog valve, only smaller. That will teach me for responding without thinking things through Craig