Two port Vacuum Advance help

[triracer67]

Replaced original 1969 351w intake and carb, with aftermarket Edelbrock stuff. The original distributor works fine and I replaced the points with Pertronix unit. The vacuum advance has two ports, can I "T" them and send to the front of the carb, or replace the vacuum advance with a single port?

 

[Rustytruck]

It is possible to swap in a single port vacuum can.
The 2 ports serve different functions. The port next to the cap is a timing retard. The port on the end is a regular timing advance port usually hooked up to ported venturi vacuum and not manifold vacuum. For a Bronco that doesnt need emission control you can leave the port next to the cap not connected but you should not cap it as it will act like a timing advance restricter. Vacuum will have to over come the vacuum created by the plugged port slowing the rate of vacuum advance just off idle.

 

[B RON CO]

Hi, X2. The easiest thing to do is ignore the port closest to the cap and just use the outer port. Your Bronco came set up with ported vacuum at the carb, but some guys like direct manifold vacuum. Good luck

 

[DirtDonk]

When the dual port diaphragm was used on models before '73, there was a very crazy connection to manifold vacuum, often for both ports.
There was a square-ish brass block as a vacuum manifold on the back of the intake with multiple ports. Then there was the springy/valvy/thingy nearby that got two or three hose connections of it's own.
They ran a circuitous route back and forth, then they went to the distributor to do weird things!

So do what they said, eliminate any of the oddball stuff you don't need anymore (if it's even still there that is) and run a single hose from the ported vacuum port on the carburetor to the front hose fitting on the vacuum advance.
Take pictures first though, in case you ever want to put it back to pure stock for a restoration. Or to help others here with the stock layout.

Unlike most people back in the seventies, and many people still here on the forums, I don't believe that all smog control stuff was evil incarnate and made only to be removed. But on a '69 and unless you have all the other stuff and want to keep it stock (it did run pretty well at that point by the way) this is one of those items I actually prefer to remove.

Back then they were literally just learning about emissions reduction methods. We'd had the beginning of the stiffer regulations for just 3 short years at that point.
All the mistakes, steps forward and back, and all the learning that has gone on in the last 50 years has resulted in what we have now. Cars from the factories with computer controlled EFI and ignitions that have 400 to 800 hp, go over 200 mph and spew cleaner exhaust than ever. And get 30 mpg as well!
Oh, and 300 hp V6's and probably even I4's that do the same thing!%)

But in the case of your '69, those pesky things can be reduced to their basic components and run a single hose.;D

Paul

 

[Broncobowsher]

When we say to ignore the port closest to the distributor, just leave it. Don't put a cap on it. That seals that chamber and that messes with the normal vacuum advance. Leave it open so it can breath.

 

[Quick & Dirty]

FYI:
The rear can connection retards timing to make the exhaust hotter at idle. This makes the air injection work better for cleaning up unburned fuel in the exhaust. If the engine starts to overheat from prolonged idling, the thermal switch on the intake shuts off the retard so it runs normal timing and cools down.

As said, if you don't need the original emissions equipment, just bypass it.

 

[triracer67]

Thanks!

Ran a new line last night, thanks for the help.

 

[DirtDonk]

...If the engine starts to overheat from prolonged idling, the thermal switch on the intake shuts off the retard so it runs normal timing and cools down.

Not sure about '67 specifically, but none of the EB's I've ever seen with the dual-diaphragm setup up to '72 had any thermal switches. At least not the normal kind we're used to seeing. The '73 and later ones had the usual suspects threaded into the intake, thermostat housing, and air cleaner housing.
Perhaps that big "beehive shaped springy thingy" on the earlier ones had some thermal properties, but I always thought it was strictly vacuum operated.

Then again, I thought the '67's came with the single diaphragm even here in CA. So shows what I know!
Now I wish I'd paid more attention to such things.:-[

Paul

 

[trekgurl]

thermactor

mine has it and I think it's called a "thermactor"?.. I want to do a few upgrades and try to do away with as much of this as I can.

 

[DirtDonk]

The Thermactor system on Fords was the air pump. Not sure if I've ever heard that they gave a name to the dual-diaphragm controller setup. Probably did and I just don't remember.
Everyone was competing to be the cleverest. GM's air pump system was called "A.I.R." for Air Injection Reactor system.

Guess we know who was cleverest most often though, as we're stuck with all limited-slip diffs being "posi" (short for Posi-Traction), all high energy electronic ignitions being "HEI" (oddly enough, High Energy Ignition) and "starter solenoids" for our starter relays, and probably plenty of other things as well.
Fun stuff.

Now someone just needs to find out what Ford called this thingy.
Thanks for the pic.

Paul

 

[trekgurl]

ok,, I thought that's what it was,,,, but,,,,, I have the "book" in my stuff somewhere,, well I printed from somewhere online ( about 45 pages). It tells all about this pollution stuff ( and what that thing is),,,and tuning of dual point set up and vacuum lines etc. I was trying to figure out what all that stuff was. Maybe I can find a link to it.

 

[DirtDonk]

That'd be great to see all the info in print. I still can't find my Ford Duraspark tech manual, but I know I still have it somewhere.

Maybe it originally came out as part of the Thermactor system, but they continued to use it even when Broncos didn't have the air pump? Not sure, but that would make sense.
First air pumps on Broncos were the first model year, at least in CA. But the continued implementation was erratic. Some years had pumps, others did not. My '71 is a Fed truck, so wouldn't likely have had it anyway. But have seen a mixture of CA trucks where some had them and some didn't.
Even my '79 F350 got one, even though it didn't have catalytic converters (over 8500 GVWR) so it's hard to know what the criteria was for them.

Hope you find the book.

Paul

 

[trekgurl]

I found it,,,,Deceleration Valve

Distributor Vacuum Advance Control Valve - Deceleration_ Valve.

So I found my document I was talking about. Printed in 1969 Autolite Engine Emisions Control Systems. It's 65 pages and I've scanned in a few pages.

One can probably search online for Autolite Engine Emisions Control Systems and maybe find it?

 

[DirtDonk]

Excellent! Thanks for posting that up.
Too bad the pic doesn't show whether the carb attachment is the manifold vacuum or ported vacuum. Might say in the text, but I hadn't read that far yet.

And for EB owners without the air pump, we don't have the temperature control switches or the air bypass valve.

Paul

 

[trekgurl]

http://www.mustangtek.com/Library6/1969AutoliteEmissionControl.html