Holley Carb Question

[stevewhitmore]

Hey Guys,
I have a Holley 650 Double Pumper and the port for the timed vacuum is plugged.
The trans vac line is going to the correct port.
The hose coming from the distributor vacuum goes nowhere and does nothing that I can tell, actually they had it plugged onto one of the the valve cover T handles on the valve cover hold downs.
Any clues what I do with the vac hose from the disti or just plug it at the disti
Thanks for any help

[67mbsc]

myself, I'd tee the existing line, and connect both to full time vaccuum.

[68Stepbed]

The dist. vac advance needs to be connected to ported vacuum. The tranny needs full vacuum. All vacuum ports on the baseplate are full manifold vacuum. The port in the side of the metering block is ported.

[prostreetC-10]

Originally Posted by 68Stepbed

The dist. vac advance needs to be connected to ported vacuum. The tranny needs full vacuum. All vacuum ports on the baseplate are full manifold vacuum. The port in the side of the metering block is ported.

When you say "ported", do you mean timed? The distributor line needs to go to the metering block because it supplies a timed signal. That means that at idle there is literally no vaccum signal so your timing will not advance and your initial will stay initial. Once enough rpms are reached, there will be enough vacuum to start to advance the distributor.

It's weird but not uncommon that someone would do that. If it was me, I'd make sure there wasn't something wrong with the vacuum can on the distributor or that there is not a crack or something in the line. You can actually take the vac line and suck on it to bring the rpms up. This will tell you if the vacuum advance is working in the dist.

[stevewhitmore]

The only two places for vacuum on the carb is on the base plate in the front where the trans vacuum hose is connected and then there is a vacuum port on the right side of the carb which is plugged.
The truck seems to run good the way it is but I know that vacuum hose from the disti always goes to the carb but I am not familar with Holley carbs, only Edelbrock.
Should the truck run good with the hose being plugged as it is now, or might it run better if I connected it to the carb?
Sorry, but I am confused with this timed vacuum stuff
Thanks,
Still Confused

[prostreetC-10]

Ideally, you should have your trans line going to a port off the manifold itself. The 3/8th port on the carb should go to your PVC. The little port under the front bowls is "usually" plugged and the metering block port is for the dizzy. You absolutely need the vaccum on the dist hooked up because you are not getting full advance under a load which will really affect performance. As the motor spins up in RPMs, the spark starts to lag behind. Having the dist advance causes the spark to catch up for best performace. You think it runs okay now......should run better with the vacuum hooked up. Granted, there is a little mechanical advance built in but you need the vacuum. If you are still confused....just hook it up!!!

[stevewhitmore]

Hi ProstreetC10
Thanks for the advice, I just went out and hooked it up but it is pouring down rain here so when it drys up I will see what it does.
The 3/8 port in the back of the carb is hooked to the PVC and the trans hose is hooked in front like the Holley instructions call for. The small port on the side is the only one left that I can see. I did suck on the hose (that don't sound good) going to the disti but I didn't get any rev change.
Thanks again

[Wrenchbender Ret]

The vacuum advance is basically for increased gas mileage. It often helps driveability at low speeds.

[prostreetC-10]

Something else you can do is to hook the vacuum advance line to the constant port under the front bowl. It should pull up the idle a bit if the vac can is working. How much idle you have and your motors overall Hg will have an affect on if this test will work or not. Best thing in the world for you to do is get a timing light....or borrow a timing light that has advance built into it. This way you can see what your initial timing is, what your total timing is and when your timing curve starts to kick in.

Are we working with an H.E.I. dizzy? The fact that you didn't get any change when you sucked on it (oh man...that just doesn't sound right) and the fact that someone had it stuck to a vavle cover bolt makes me wonder if there is something wrong with it. You can replace those vac cans and they are pretty darn cheap. Having a correctly working vacuum advance dizzy will have a big affect on overall streetability because the dist will "sense" when to start to advance.

[stevewhitmore]

Yes it is an HEI Distributor with what appears to be a new cap and the vacuum canister looks like it could be new as well.

[prostreetC-10]

hmmmmmm

['72customdeluxe]

timed vacuum is pretty much only better for emissions (with air injection, cats etc.), helps cat light off. Worse fuel economy and rougher running that way in my experience with my truck. I would just tee it off as mentioned before.