Holley 4160 Metering Block vacuum line?

Posted By: sharpie

Holley 4160 Metering Block vacuum line? - 05/13/09 05:56 PM

I remembered something kind of important - when I was rebuilding my Holley 4160, I broke off a line barb on the main metering block (above the idle mixture screw):

Will this have serious consequences? I ended up connecting the vacuum advance for the distributor to the base of the main body. You can see it just under the primary fuel bowl in the picture.

Posted By: CJK440

Re: Holley 4160 Metering Block vacuum line? - 05/13/09 06:01 PM

Thats ported vacuum which should have zero vacuum at idle and what your vacuum advance should be connected to.

You can probably drill it out and press/epoxy in a metal tube.

Posted By: GomangoCuda

Re: Holley 4160 Metering Block vacuum line? - 05/13/09 06:04 PM

The one on the base plate is manifold vacuum instead of ported vacuum. Vacuum advance is not normally connected to manifold vacuum. A few people like to use manifold vacuum and who knows there may infact be combinations that it would work good on.

Posted By: sharpie

Re: Holley 4160 Metering Block vacuum line? - 05/13/09 08:11 PM

So, there's three vacuum ports as far as I can see. The first is the one which my vacuum choke attaches to. The second is the metering block, the third is the one under the primary fuel bowl. Just so I'm clear, which is which and what gets plugged in on the other side of each? Thanks,

Posted By: Dodgem

Re: Holley 4160 Metering Block vacuum line? - 05/13/09 09:00 PM

one underneath soulld be manifold Plug it it's only for checking vacuum.
One in the metering block is ported vacuum plug it too!!!! LOL!! (or if you must hook to vacuum advance.)

Posted By: Dodgem

Re: Holley 4160 Metering Block vacuum line? - 05/13/09 09:03 PM

I would run lighter springs in the dizzy and forget the vacuum advance it is a crude cruise gas mileage feature and if not on the right port totally wrong!!

Posted By: RapidRobert

Re: Holley 4160 Metering Block vacuum line? - 05/13/09 09:12 PM

Quote:

So, there's three vacuum ports as far as I can see. The first is the one which my vacuum choke attaches to. The second is the metering block, the third is the one under the primary fuel bowl. Just so I'm clear, which is which and what gets plugged in on the other side of each? Thanks,

(1) correct (2) metering block one is ported for the dist if you use ported dis vac & most but not all apps do (3) extra manifold vac source for air cleaner hot air door vac servo or any other needed full vac source,& good for checking manifold vac level, cap it with a plastic vacuum plug if you dont need it.

Posted By: Crizila

Re: Holley 4160 Metering Block vacuum line? - 05/13/09 11:48 PM

If you are driving on the street and your distributor has a vacuum advance unit on it, use it. Most Mopars ( from the factory ) ran ported vacuum. If you are running stock stuff, run ported vacuum. If you are running a pretty hot cam and have idle issues. switch over to manifold vacuum. The extra advance at idle will help with idle quality. Mileage will be better if you use the vacuum advance, not to mention the motor will run cooler.

Posted By: Dodgem

Re: Holley 4160 Metering Block vacuum line? - 05/13/09 11:56 PM

Quote:

If you are driving on the street and your distributor has a vacuum advance unit on it, use it. Most Mopars ( from the factory ) ran ported vacuum. If you are running stock stuff, run ported vacuum. If you are running a pretty hot cam and have idle issues. switch over to manifold vacuum. The extra advance at idle will help with idle quality. Mileage will be better if you use the vacuum advance, not to mention the motor will run cooler.

People who know nothing about tuning a performance car compensate by putting the vacuum advance on manifold vacuum. It helps hold the idle for those with lack of tuning ability. But at WOT there is no vacuum and you give up a huge amount of Performance! Some people should not be offering up advice period!

Posted By: marklock

Re: Holley 4160 Metering Block vacuum line? - 05/14/09 02:58 PM

Posted By: CJK440

Re: Holley 4160 Metering Block vacuum line? - 05/14/09 03:06 PM

One problem I have seen with using manifold vacuum is that get into a loop where

1-RPM fluctuates and affects vacuum
2-which affects the ignition timing at idle
3-which affects the RPM,
4-go back to 1.

Ported vacuum works just like manifold vacuum to give you the same vacuum timing affect during cruise, but "shuts off" at idle.

One other thing, if you do have vacuum at the ported vacuum barb at idle you can be reasonably sure your idle screw is opened too far and you are going to have other drivability/tunability problems.

Posted By: dmerc

Re: Holley 4160 Metering Block vacuum line? - 05/14/09 06:36 PM

Ive got about 8 inches of vacuum on my ported vacuum connection Its a quickfuel metering block. what's with that?

Posted By: Crizila

Re: Holley 4160 Metering Block vacuum line? - 05/14/09 07:21 PM

Quote:

Quote:

If you are driving on the street and your distributor has a vacuum advance unit on it, use it. Most Mopars ( from the factory ) ran ported vacuum. If you are running stock stuff, run ported vacuum. If you are running a pretty hot cam and have idle issues. switch over to manifold vacuum. The extra advance at idle will help with idle quality. Mileage will be better if you use the vacuum advance, not to mention the motor will run cooler.

People who know nothing about tuning a performance car compensate by putting the vacuum advance on manifold vacuum. It helps hold the idle for those with lack of tuning ability. But at WOT there is no vacuum and you give up a huge amount of Performance! Some people should not be offering up advice period!

Right! Vacuum advance has nothing to do with performance - at WOT. Vacuum advance is ment for idle and cruise, when you want to lite that mixture earlier to maintain that peak cylinder pressure at 10-15 degrees ATDC. On engines with big cams where you need lots of air at idle, running manifold vacuum ( dumping in an extra 8-10 of advance )can help keep you out of the fuel transition slots by letting you close those throttle blades a little bit - improving idle quality. Did I mention it helps the engine run cooler?

Posted By: CJK440

Re: Holley 4160 Metering Block vacuum line? - 05/14/09 07:35 PM

Quote:

Ive got about 8 inches of vacuum on my ported vacuum connection Its a quickfuel metering block. what's with that?

The ported vacuum tap "should" enter the barrel at a point above the butterfly blade where there is no negative pressure at idle. When the throttle opens the leading edge of the throttle blade moves up past the hole and Ported vacuum now behaves simiar to manifold vacuum since they both reference a point below the throttle blades now.

If you see vacuum at the ported vacuum fitting at idle it means the throttle blade has moved too far and uncovered the hole. The throttle blade also probably uncovered too much of the transition slot and you are suffering problems getting the ideal idle mixture right.

If it were me, I'd adjust the secondary idle stop screw to open the secondaries a little more and back off on the curb idle to get the throttle blade position back where it should be. You could drill holes in the primary plates but those are hard to reverse.