carb vacuum query

Anonymous · Post by **Anonymous** » Tue Aug 10, 04 2:51 pm

Fitted the 'mystery'(holley 600) carb to my 318, ran much better than my existing Holley 600 but, vacuum connections seem wrong. There is no port for vacuum other than at manifold level. I have blanked off egr and other small vacuum port (rear of carb). Where should advance vacuum be connected?

Dave-R · Post by **Dave-R** » Tue Aug 10, 04 3:12 pm

Any port that gets its signal from above the throttle blades rather than below. On most Holleys the port in on the metering block between the fuel bowl and the body. Same place the idle mixture screws are at. Not sure which family model this carb of your is?

Anonymous · Post by **Anonymous** » Tue Aug 10, 04 3:38 pm

That what I thought, Dave. There is no vacuum port above the throttle blades. Carb is essentially a 600cfm (details in post below this one). I read somewhere (web) that vacuum can be connected to manifold vac port . Runs well anyway!

Dave-R · Post by **Dave-R** » Tue Aug 10, 04 4:23 pm

I would not connect it to manifold vacuum. You will have a lot of timing at idle which will effect your idle speed settings. You can get away with that though if you feel you must.

For myself, if it really does not have a dizzy vacuum port, I would rather run without the vacuum advance. It is only there to give you better mileage during light load part throttle situations.

Dave-R · Post by **Dave-R** » Tue Aug 10, 04 5:18 pm

OK so it is a 4160 model?

Well in that case it should have a metering block between the fuel bowl and the carb body yes?

What is just above the idle mixture screws on your carb??

Look at this photo of one of my 2bbl carbs. This should be the same as the PRIMARY side of your carb. I am pointing to the vacuum port for the dizzy. Some people blank this off on race cars because they don't need it. If yours is missing you can get (or in my case make) one.