Vacuum Hoses

[Bitzer!]

Hey guys,

You can tell things are moving on by the amount of questions coming your way!

What would be the minimum vac hoses required?

I'm guessing from dizzy to carb, and top of inlet manifold (by the dizzy) to the side of the g/box?

There were all sorts of hoses going here there and every where before removal but they were so perished and loose I'm not sure they were actually doing anything. The thermostat housing has a plug type thing with vac hoses coming out but not long enough to reach anything.

I don't have any smog issues etc over here and looking to keep pipwork/wires to a minimum and out of site.

Checked the Tech section (back to 2006!) but couldn't quite reach a decision!

cheers again

Andy

[Jason S]

Howdy,

Aside from vacuum hoses for the carburetor to function (e.g., choke pull off), the minimum amount of vacuum hoses would be a hose from the ported vacuum source on the carburetor to the distributor and a hose from the PCV valve in the valve cover to the carburetor.   

Additional vacuum hoses will be needed depending upon options and accessories, such as:  Automatic transmission- you would need a vacuum hose from the intake manifold to the transmission;  Vacuum Power brakes- a vacuum hose from the back of the carburetor (or intake manifold) to the vacuum brake booster;  Air conditioning- a vacuum hose from straight vacuum (on carb) to the air conditioner vacuum reservoir on firewall.

Emissions equipment required additional vacuum and temperature operated switches to ensure the engine was operating within specs for the truck's particular emissions category.  The more stringent the emissions (e.g., California emissions on a 1/2 ton pickup), the more spaghetti mix of vacuum hoses and switches. 

Hope this helps. Good luck

[bake74]

     Jason S hit it right on.  He covered the basic's, the rest is up to which options your truck needs vacuum to operate.  Good luck and keep us informed on how your build is going.

[Bitzer!]

Jason S - cheers fella, easy to understand too!

If all goes to plan, I'l be able to fire up this weekend.

Bake - It's you guys that speed the process up no end! Without the help it'd be a nightmare!

European 4 pot stuff is easy over here, anything bigger and we struggle 

[Bitzer!]

Ooops, one last question on this!

The carb is a 750 Holley, I can only find vacuum at front and one at the rear. Is it acceptable to "T" off the rear one to the valve cover or should it be off the front one OR either is fine?

Getting there!!

cheers

Andy

[Jason S]

Here's a link to the Holley instruction manual for the fairly common Street/Strip 750:

http://holley.com/data/Products/Technical/199R9934-3rev1.pdf

Take a look on page 6.   The port on the rear of the carburetor is for the brake booster vacuum hose.  On the front is a port near the bottom with full manifold vacuum where you can connect the PCV hose. The ported vacuum fitting for the distributor is on the side of the carb near the choke thermostat above the idle mixture screw.

If you have a different carb than the Street/Strip, you might look around on the Holley website for manual on your particular carburetor. However, other versions of the Holley carb should be similar.  Hope it helps.

[Bitzer!]

Again, cheers for the help. Most of my 'net work is done from my phone. The PC I have keeps crashing so almost reliant on you guys!

[Bitzer!]

Oh me Oh my!

Had a quick look at the carb, found the Timed Spark Vacuum source that I'd missed. It had been blanked off and had been for a while by the look of it. Doess this mean they used alternative source or set the dizzy and ran with no advance?

Wouldn't it be nice to wave a wand!!

[Donut]

They may have used full (manifold) vacuum off of the carb or a vacuum "tree" in the intake. 
My trucks seemed to run better off of the full vacuum.  (some folks do prefer ported vacuum)