I run a vac advance distributor (with EZ-EFI) and need a ported vacuum source. I have read that the small fitting under the TB (former EGR vac) is ported; also read the fitting under the fresh air/CCV nipple on the right side of the TB is also ported. Which would be better to connect my vac advance to?

Note: I had been running that advance from the plenum vac port, which is apparently manifold vacuum, with really bad results.

 

Both passages connect and are both ported. The small one under the tb will be the easiest to attach to.

 

Thanks man.

 

The CCP port drops straight in behind the butterflies and has constant ( not ported ) manifold vac

 

Depends how your dizzy vac advance can is calibrated
Some enlightenment
http://www.digitalcorvettes.com/foru...74&postcount=3

"Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration.
After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements,
and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream.
One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from
below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle.
This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value),
and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC).
This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness
of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system;
as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures
went up,combustion efficiency went down the drain, and fuel economy went down with it.

If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back.
The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - ported vacuum was strictly an early, pre-converter crude emissions strategy, and nothing more. "

 

I had to check to refresh my memory got me oz

 

On another topic op, how is your EZ-EFI treating you? I have 3 friends with it all ordered within a yr and a half of each other and they all have had issues. (FAST says on 2% are having problems, our small sample is 100%)
One had a inj driver crap out in 20mins of install run time.
Another one will not communicate with the hand held unit.
and another has had running issues since day 1, new harness,new ecm new dizzy new this and that.
Hope you have better luck.

 

I had decided to use the small brass fitting on the bottom of the TB because it fit the vac tube. One correct choice made..

Vetteoz: I have seen you post that before, however I don't really know if it applies to my situation. I am running the 8361 MSD ProB distributor, and in the literature it says to connect the vac can to a ported vacuum source. I'm not saying your info is wrong, but I originally had that vacuum line connected to the plenum, which is manifold vacuum. Car has only one issue, it can't keep a steady idle...see below.

TTOP350: I do not really know what grade to give the EZ for one reason, I don't think I know enough to make everything work right the first time (i.e. where ported vacuum is). I cannot say for sure that it is the EZ that has had me pull my hair out for the past 2 years. My problem has been and still is that the idle quality just plain sucks. I can get it to hold a steady idle sometimes, and other times not. No real rhyme or reason why it starts bouncing around. Had to hook the MAP, AFPR, vac advance and HVAC ball up 3 different ways and am just now trying the third. Turning the electric fans on makes it worse. Why? I am certain of one thing: plug-n-play it is not. Although it does do a very good job of tuning while the wheels are turning, getting it to purr smoothly does take some doing. Perhaps, again, it is simply my apparent lack of tuning skills (which is why I got it in the first place). Perhaps some folks can spot the issue right away; 2 years, 8 different "solutions" (yes I put a vac guage on it) and dozens of support calls later, I still cannot. I have posted the dyno results and that alone makes this system worth the effort. Granted, it has taken 2 years because I cannot work on it every day, or even every week. Most of the time I just get frustrated and rather than torch the whole car in an open field, I just walk away. Not to mention I also have about $1500 invested. If I cannot fix it this round of attempts, I am seriously contemplating selling it. For all practical purposes, I will not drive the car (weekender) while it acts like this. It's a pretty car, looks mean,until I pull up to a light and my idle is bouncing around making me look like an idiot.

At this point, I am switching the MAP and distributor vacuum around and increasing the fuel ratio to around 13.5 at idle. Still need to work out a hesitation when I stomp while rolling but I think I can fix that.

 

A friend of mine is on the hot rod power tour right now. He's had about the same issues as you since day one. The FAST guys are throwing parts at it like crazy and nothing is working. I have 3 friends that have it and they are all having issues.
FAST says only 2% are having issues but every time I hear of someone with it, I hear of more of the same issues.

 

You will want to try leaner idle mix and give it timing. Tune idle for max vacuum.Mild motor should see 22-25 deg at idle, some maybe more. Bigger cam may want 26-30. Thats why i like stock efi with programmable timing tables lol. Can dial in what it needs and lock idle area timing for more stability

 

Orr, right now (before I've tried anything) the ratio is around 14.5/14.6. It has 10 deg base right now (35 full adv). I'm using a 25 deg stop bushing but have a 28, 21, & 18 deg SB available if need be.

You are suggesting 22-25 deg with vac advance connected right? If not, then I'd have around 50 deg full advance.