I will have 4 items needing vacuum...
PCV
Brake Booster
Dizzy Advance
Adjustable Fuel Pressure Regulator

I know the booster needs to be hooked up to a direct source for constant vacuum but which of (or all) the other three need to be hooked up to vacuum only when the throttle is opened?

 

Only the distributor advance will need the timed vacuum port.

 

Depends on your cam. When I was running my carb setup with comp cams 288XR I made very like vacuum at idle, only 10" IIRC. I had the MSD dizzy with vac advance. The problem was the can was set to come in at 15" and I never made the 15" to activate it. So what I did was set my Mech curve for 15* at idle then 36*-38* all in at around 3000 rpm. What I did was use an adjustable vac can instead of the stock one that came with the MSD. I had it set to the lightest setting and just made a small stop with how much I wanted. The adjustable can would add 20*-25* and I only wanted around 15*. So with that installed, I had around 30* total at idle. Engine idled very smoothly and cool at ~800-825 rpms. Then when I was cruising the total timing was in the low-mid 40's allowing me to use less gas and get decent mileage.
My suggestion would go with a direct port for the vac advance.

I had my BB directly off the manifold.
PCV to the back of the carb.
Vac can to direct port on the carb.
Never hooked up the boost reference on the AFPR. (it wasn't necessary as I wasn't running any power adder).

 

Thanks Ward and Thomas. IIRC the AFPR needs the vac line hooked up under any circumstances, not just for boost but I'll go double check that.


Oh, and I am also going to have to seriously tune this dizzy like you have done. Its an eBay special and I was having some issues with the advance the last time it was up and running. For some reason it was maxing out the timing (with the vac advance hooked up) extremely soon...
I also have a feeling with the cam I will not pull much vacuum at all.

 

The PCV also needs to be connected to a dedicated PCV port, not just any old vacuum port.

 

Is your vac advance adjustable on the distributor? I READ A REALLY GOOD ARTICLE IN THE TECH SITE HERE ABOUT ADJUSTING THE ADVANCE AND THE TIMING SO YOU HAD ALL THAT YOU NEED.

 

The fuel pressure regulator doesn't need vacuum unless you run boost.

 

Would help to know what intake manifold youre running.

I have my brake booster going to the back of my holley carb. Edelbrock, and Q-jets have these as well, its basically the biggest vacuum port on a carb.

Then i have a fitting in my manifold, that is split amongst PCV, and two other hoses running gauges. Both interior and underhood.

My charcoal canister is hooked up to a little vacuum port at the front of the holley, and the timing is hooked up to the timed port. However, i was getting irratic behaviour for timing so i swapped the last two. You may decide that the timing prefers the timed port...

DO NOT SPLIT YOUR BRAKE BOOSTER HOSE. This is why i put mine at the back of the carb, because in the event i need to tune the carb or remove it, i only have to remove one hose, and not juggle with 3.

 

Apeiron What would be a dedicated PCV port/how would this differ? I have two direct ports (one small one large) on my Demon and one small timed port.

I am running an Edelbrock Air-Gap RPM with its one basically useless vacuum port towards the rear. I will be tapping another one or two, however.

rodrob1961 I'm unsure if this cheap thing is adjustable but I will make it. Need to do some more in depth reading on dizzy's and will hopefully solve that after I get the car running.

Also, it seems like the vac advance dizzy port will be a trial and error thing between the timed or direct ports.

online170 The brake booster hose will not be split. I did that earlier with the PCV when I added it and found out I lost 30% of my braking pressure The car still stopped fine but this cam should have even less vacuum...

five7kid Here's what my AFPR manual says about the vac port:
"This regulator is equipped with a vacuum/boost compensation port that can be used to momentarily decrease fuel pressure (vacuum compensation) at idle and part throttle, or increase fuel pressure under blower boost (boost compensation). While it is not necessary to connect a hose to the vacuum/boost compensation port, it may be beneficial in some cases. However, the small plug on the barb must be removed prior to use."

So it looks like it will also be a trial and error type thing.

 

Yea i am also running the RPM air gap, with a Holley DP. See if you can close your hood with a 1/4 inch gasket. if so, you might be ble to get away with using your vacuum port. Thats the combo im running, and it was a tight fit, requiring a little "triming" on my hood. However, i have a GTA hood, which has a frame underneath. The camaro hood might not. However, drilling 1 or 2 new ports is probably smarter, and easier.

if you dont need one, you could just plug it.