Original Distrubutor 75,76,77

[pbets756]

Can anyone with their original distributor and smog equipment please take a look and see how many vacuum lines on the distributor. They have single or dual lines. My 76 I am getting close to finishing had the original distributor replaced with a points set up years ago by the gentlemen who bought it new and we couldn't find the original in his shed. All the other smog equipment is there yet and I want to keep it original as it has only 52000 miles. I'm about to purchase the distributor and new smog pump and want to get it correct. I am going with the Duraspark II which comes with either dual or single. thanks Paul

 

[Rustytruck]

Take a picture of your emissions decal on your valve cover if its there. It will show what emission equipment package the engine was built with. It will also help if you have the DSO # from you vin tag and can sort where the truck was actually sent after being built and that may help identify what emission package was originally on the truck.

Distributors are tough to sort out since there were so many variations between the models of cars and trucks and emission packages for each one. I believe the Factory service manuals has a break down for each model and there is usually about 6-8 different part#s that could be used in the same model truck or car depending on where its sent. Some distributors had Identification metal tags or part numbers stamped on them. They all had different weights inside or different vacuum canisters with different vacuum advance calibrations.
Not that you need a specific Distributer as any of them can be recalibrated to what is needed. They can make or break a a vehicle with a full package of emission equipment back in the mid to late 70's.

 

[pbets756]

Mine was shipped to Nebraska dealer then went to a dealership in NW Iowa where the precious owner bought it new. I wish he would have kept the original distributor. it has smog pump and all the lines to the air cleaner. I have all that. I had the motor rebuilt so the stickers aren't there anymore but I bet I have pics of the decal cuz I took lots of the engine. maybe I should forget about keeping it original and take the smog stuff off but its all there except the darn dist. thanks paul

 

[Rustytruck]

Does your truck Have Catalytic converters? Does the dash gage bezel say unleaded fuel only under the speedo needle?

On your intake manifold do you have a water controlled vacuum switch by the thermostat? They can have 2 or 3 nipples on it.

Do you have EGR valve at the back of the intake or attached to a spacer under the carburetor?
You say you need a smog pump do you have the diverter valve and the hoses going to the heads with the check valves on the ends? Do you have air injection tubes going into the heads right over the exhaust ports.

My 1974 California smog monster came with a dual canister distributor but it doesn't have the same system at the 1975 when the cats and unleaded fuel came in.

Post some good pictures in and around the engine compartment of what you have would help.

Some of these engines used two water heated vacuum switches to control the timing through the end port of the vacuum canister. one to control normal ported vacuum and another to add manifold vacuum to the vacuum canister to raise the idle if the engine gets too hot. The second port by the cap was used to retard the timing when at Idle to reduce Nox and to lower the idle to prevent engine run on with the leaner fuel mixtures working in conjunction with the idle solenoid.
I know the vacuum diagrams for the most common stuff and pictures are on this site but it will take a whole lot of searching to find them.

Do you know what the production date on your Bronco was?

It is unfortunate after all these years that we haven't compiled concise information on Smog equipment for each model year. I guess it just wasn't important as these trucks were less valuable so everyone started abandoning these failing systems and converting back to basics. Now that stock trucks are so valuable we just don't have the basic information to restore these systems and we have to peck and see little bits here and there.

Use to be just a California problem, now its other states and a collector restoration Issue.

 

[DirtDonk]

Even the '71's and '72's had the dual-diaphragm distributors, but with fewer controlling components to deal with. After '73 those engine compartments were getting pretty full!
The CA-equipped '76 we have at the shop had a dual-diaphragm distributor.
I've seen some '77's (I think) that had only one, but those are the only ones I think I ever saw from the factory that way after about '69 or '70.
A couple of guys still have their purchased-new '77's here, so maybe they'll know.
jckkys? Maybe bluebuckaroo too, but I don't remember what year his is.

Paul

 

[jckkys]

My '77 had one vacuum nipple on the distributor ie. no vacuum retard from the factory. The '77 Ford truck shop manual has no diagram or other information that indicates any 302 had a vacuum retard. If California emissions were different, there is no mention of it. My '73 Bronco did have two nipples. A '76 460 car I owned came with one nipple. It seems the addition of catalytic converters made the retard unnecessarily. I'll check a '72-'78 Motor Manual I have, since they made a real effort to describe the emissions equipment in cars for those years and EBs had a GVW so light that the equipment was the same as cars. High GVW trucks escaped some of the emissions requirements, including cats.

 

[pbets756]

Thanks guys. My 76 does have a catalytic converter on it and the unleaded gas printed in the dash. I know where all the vacuum lines go as they were all hooked up when I bought it. The only line that has been plugged is the one coming off the carburetor located on the bottom/middle coming out the passenger side of the carburetor. not sure what went to that. I will post a picture tomorrow. I was thinking of leaving the catalytic converter off when I finish the exhaust, maybe I should put a new one on if it is needed. thanks again Paul

 

[DirtDonk]

In some instances at least, both the vacuum hoses you describe go to the distributor, but not directly. They run variously through the thermal switches described earlier, through multiple paths before they get to do the actual work at the vacuum advance can.

In '74, CA spec Broncos got the early Duraspark setups with the small caps. I think FED spec still had points until '75, when they all went electronic.
Pretty much the same with catalytic converters. CA trucks had them in '74 (nope, '75 it was), but ALL Broncos came with cats from '75 (or was that '76?) on up.

Thanks for the info on the '77's jckkys.

Paul

 

[pbets756]

Here are some photos of the engine and carb with the smog stuff before it was rebuilt. On the one carb picture is a short rubber line that is plugged off. anyone know what went there. thanks for all the replies.

 

[jckkys]

My further research using the Motor Manual reveals the '76 vacuum routing is identical to the '77. The Duraspark distributor has just one nipple on the vacuum advance. The 2150 carb has a so called EGR nipple on the front below the accelerator pump that is capped off and not used. On some vehicles, this was used to open the EGR valve. Of all the knuckle head things POs have done to EBs, removing a Duraspark ignition system to run points is near the top of the list. Even within this description there are several sub systems that differ with local emissions requirements.

 

[pbets756]

Thanks so much jckkys for your help. Who would have thought it would be so difficult to find this out. Maybe I'm a fool for putting it all back to original but that's just what I want to do. I went to my local parts store to order the Duraspark II and he had no idea what I was talking about. He said it doesn't list what kind of distributor it is other than rebuilt. I checked with Ford dealership and they are no longer available. thanks again Paul

 

[Rustytruck]

No 1974 Broncos in California didn't get cats only the cars. Bronco was exempt due to being a truck. But they did get the duraspark in California where 49 state still had points. The 1974 Bronco had a 1 year only very complicated amplified vacuum system. There were 2 other districts that got the duraspark in 1974 but I don't remember where it was.

My Bronco was an original 1974 delivered to Los Angeles California

 

[Rustytruck]

You have to remember back in the day a replacement Duraspark module was only available from Ford and very expensive. I had to pay almost $140.00 for one new from the dealer. Minimum wage back then was about $2.30 and hour Points distributors were a whole lot easier to get, cheaper and everyone was familiar with them.
Modules didn't get a whole lot cheaper until we all sold out to the Chinese. And we all prefer the original used one's made by Ford.

 

[jckkys]

The original ignition system WAS Duraspark on '76-'77 Broncos. So the replacement parts would all be Duraspark on any '76-'77. If you're dealing with a kid on a computer, go to a real parts store, not O'Rielly's or AutoZone. Ask a repair shop where they get their parts, if you don't know what I mean. '74-'75s had what Ford called electronic ignition that only resembled Duraspark. The module and wiring harness were different.

 

[jckkys]

The early modules over heated and killed the engine. By early 1978, I had mine replaced with a new Motorcraft module on warranty, that supposedly fixed the problem. This one went till the mid '80s. The 3rd one is still in the truck. New US made Motorcraft modules are still available if you're willing to make the effort. None of these were more than 60 bucks. I remember it all quite well. At no time did I consider going to points. Points were always a PITA.

 

[Rustytruck]

You insuating I am a liar?

 

[jckkys]

No, just uninformed. I can provide reference cites for my information, if you dispute any specific assertion.