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Ported versus manifold vaccum.

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Okay, I dug out one of a huge supply of manuals.
1969 Ford Official Shop Manual, Volume 2, Engine, page 09-02-02, under the section Distributor Dual Vacuum Advance:
Paragraph One:
The inner (secondary) diaphragm is actuated by intake manifold vacuum to provide additional ignition timing retard during periods of closed throttle deceleration and idle, thereby assisting in the reduction of exhaust system hydrocarbons.

"reduction of exhaust system hydrocarbons " is emissions control.

I gots more.......
 
TOC said:
The two-port advance on Fords was ABSOLUTELY emissions related.
I worked for Ford when they came out, and was a state-certified emmissions specialist.

Ported vacuum advances on basically ALL Fords from 1949 until they went to the EEC system.

The retard was off a TCVS (Temperature Controlled Vacuum Switch) which operated diminished performance until warm.

BB's seemed to find their way into those hoses with regularity.
Click to expand...

We are talking about two different systems. The one I was describing was on, for example, my 1968 Cougar 302 with AC without thermactor, and was used with the single diaphram advance dashpot in California. I'm hip to the system you are describing. I guess that system was not used for long after 1968, I thought I saw in in 1972.

Speaking of BBs, I did the opposite once. I had a Q-code '72 Torino with an Edelbrock F351-4V (pre-Performer) intake and had to smog it. So I grabbed a squarebore EGR plate from a Lincoln, filled the underside chambers with silicone and painted the intake blue with the logos covered with silicone and sand. I added a hose nipple to the side of the plate and ran a hose behind the engine down by the trans, and then I hooked up the stock vacuum system. When I got to the check site the car passed the sniffer and then the tech used a vacuum pump to open the EGR valve at idle. The engine stumbled like it was supposed to. Approved. Funny that he didn't flag the 3310 Holley.
 
TOC said:
Okay, I dug out one of a huge supply of manuals.
1969 Ford Official Shop Manual, Volume 2, Engine, page 09-02-02, under the section Distributor Dual Vacuum Advance:
Paragraph One:
The inner (secondary) diaphragm is actuated by intake manifold vacuum to provide additional ignition timing retard during periods of closed throttle deceleration and idle, thereby assisting in the reduction of exhaust system hydrocarbons.

"reduction of exhaust system hydrocarbons " is emissions control.

I gots more.......
Click to expand...

The system I am describing is in 1969 Ford Car Shop Manual, Vol 2, page 09-01-20, fig. 37.

Man, are we nerds or what!
 
The interesting bit is that's General Misunderstanding.
The cams, heads, carbs were designed for straight manifold, like almost from day one of the V-8, while Fords were ported.
I know, absolutely, what happens to performance on my Fords if the diaphragm goes, and I get no increase in advance with increase in differential pressure across the throttle plate.

The dual-feed diaphragms of the late 60's, 70's and sometimes early 80's were a CARB and FED band-aid.

I have run straight mechanical advance, and removed it (dual-point, mechanical Mallory) as it did not perform as well as my stock distributor (acceleration, power going over the pass, and mileage).

You run a GM on ported, when the distributor, cams and such depend on manifold, and the diaphragm actually dropping away when you nail it, you've got serious issues.

Had an old Ford in the shop a while back, with an AFB (and I won't tell you what that stands for) that just would not get out of it's own way, no matter what you did.
The AFB had NO ported vacuum source.

Nothing I could do with it to make it right.
 
Please note:
I think I was fairly specific on using what your vehicle came with and was designed for, rather than swapping lines around.

Quadra-Flush and Thermo-Toilets (QuadraJet and ThermoQuad) cover up the bogs with a very rich mixture at times in their cycle.

When you dump two 2" (I know...but they LOOK that big!) secondaries on top of primaries being wide open......well, more gas can cover a multitude of sins.

One of the "tricks" to get GM's to idle was to pop the Fed plugs out and richen idle mixture by a bunch.

To change to subject slightly.....

Remember US Variable Venturi carbs?
In the dealership and shop, I seemed to be the only guy who could get them to work.
Never could figure out why, until years later.

They were a variable choke.....sort of like an SU.

The things they tried to get emissions down.....

I remember Midgets with a catalytic converter UNDER the intake manifold.
The heat from that setup sure made short work of carb gaskets.
 
So, I guess the question for me is how should I hook up the vacuum advance with a 1275 (very mild upgrade) with a Flame Thrower distributor. The SUs are of the ported design. Sould I use the stock vacuum advance on the dizzy, not use a vacuum advance, and if I do, do I hook it up to the ported connection or to one on the intake manifold?
Thanks,
Scott in CA
 
You can experiment, but if the distributor is a direct replacement style, set up for your car, I would ALWAYS start with the original design hookup.

Let me give you an idea of the odd things that can happen.

I have, somewhere, a Ford Technical Service Bulletin from 1967 or 1968 on 289/302 V-8 and rod knock issues.

Rod knock. New cars.

Seems someone on the assembly line decided to connect up some of the vacuum advances to manifold vacuum, and at idle, a low end knock was being diagnosed and opened for repair.

The "fix" was to put the advance line back where it went.

I have watched all sorts of "experts" try to re-invent the wheel, so to speak, over the decades.

Intake port match, then mis-match, then match....cams, tuned headers, some work, some make no discernible difference....even to the point of welding the breaker plate and disconnecting the vacuum advance unit.

Seen that.
 
So, a stock set up would be ported vacuum on HS2? I seem to recall there being a good pull off that line at idle so maybe it really is manifold? This is an easy question to answer I know, go check, but I can't. Just curious. I assume, back when the A series and ignition were set up in '63, it would be conventional manifold vacuum pulling on a regular vac. advance set up. Maybe if I'm lucky I'll have a chance to play with my car tonight and check. BTW, what would be a good target for full advance at, say 3000 rpm? 32ish? by then you'd be at max advance right?
One would:
disable the vac advance by pulling the line and plugging
idle car at 700ish
set idle at 8 BTDC (spec for my 1098)
reconnect vac advance (should see a few more degrees advance now, still idling, how much?)
rev engine, and advance should increase with revs to about 24ish advance, so you had 8 initial, 24 mechanical (vac advance not in effect at 3000 rpms) for 32 total.

For more enjoyment tuning Lucas dizzy
 
What ever your car/carb/dist setup was, start there.
Some were manifold, and fogy memory banks indicate the easy spotting feature was the vacuum line went to the fitting on the intake log.
 
Since starting this post I would like to appologize for not participating. My computer took a dive the next morning. Thanks for all of the excellent info. More than I really want to get involved with just now. TOC has the best plan and that is to go with the system the dizzy was designed for. I went to these carbs because the original carbs have the crankcase vent fitting and I could'nt get the car to run without falling on its face at 3K and up until I filed the needles ala Visard. Ran OK but hard on fuel. Engine I believe is stock except for maniflow. If I plug the crankcase vent fittings on the carbs and get ahold of the correct data on springs and needles will these carbs be satisfactory? I would then use a pcv setup for crank vent.
Thanks again, KA.
 
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