Ok ya'll, where are all the vac lines that need to be plugged? Man we keep finding those things every where seems like! haha I just want to make sure we aren't missing any. Can someone give me a detailed walk through of where they will be (diagram on the hood isn't worth the paper its printed on). If someone could provide pics of all the different vac lines that'd be GREAT. We can't get it timed right till we have all those plugged. We thought we had them all plugged so we got it timed and then we could hear a slight air noise so we got to looking and there was a vac line over by the passenger wall that was coming from something up right in the top left corner of the engine bay. There was a little bolt coming out of this little canister looking thing and when we would plug the vac line, that bold would move! Not sure what that is. It looked like it was supposed to be plugged into this round, softball size ball thing right behind the battery so that's where we put it for now till we hear if that is wrong. Anyway, if anyone could post pics or a detailed description of the vac line routing I would GREATLY appreciate it.

Also, we were trying to time it via a vac gauge but we weren't sure what it was supposed to read at idle so if anyone knows that, that would be great too! Thanks gang!

 

Can you take pictures of the part you're talking about? Trying to visualize it, but can't.

Okay, first off, what stock parts do you still have and want to use? Air cleaner warm air valve? (the one that's in line between the hose coming from the grill to the air cleaner), charcoal canister? EGR valve? Etc. Much of the vacuum line routing will depend on what you still have on the engine and what you want to use.


If not, and all of that is removed and you simply have the carb with nothing else.
All you need is:

Line from ported vacuum to the vacuum advance on the distributor.
Large line from full manifold vacuum to the PVC valve.
Large line from full manifold vacuum to the brake booster.

Everything else should be capped off, except for the large port coming out of the front of the carb. That's a fuel bowl vent.



At idle, once all vacuum lines are sealed and the engine is nice and tight, and the engine is fully warmed up, you want to adjust the idle mixture screw until the vacuum is as high as you can get it. Readjust the RPMs until they're at 700. Readjust idle fuel mixture to highest vacuum, readjust RPMs, etc. until no more adjustments can be made.

Disconnect vacuum advance from carburetor and cap it off so it's not pulling vacuum. Advance the timing on the distributor until you get the highest vacuum reading possible. Then back it down 2hg. (Ie. highest reading = 20. back it down to 18)

Anywhere from 18 - 21 is a nice, good vacuum. The higher your elevation, the lower the number will be. (And visa versa)


Take a couple pictures of your engine bay so we can see what you still have in there after the conversion.

 

Thanks AB!! That info is VERY helpful!

As of right now, we haven't removed anything. We weren't sure what all we could remove really. Kind of scare to start pulling stuff off you know! ha

Anyway, here is a picture of the little thing at the top left corner of the engine bay. The rusted little bolt sticking up on the right side of it will move left and right when you plug/unplug the vac line coming from it.



And here is the large ball object directly behind the battery that we think this vac line plugs into. We aren't sure on that though.

 

Hrmm... Don't have that stuff on either mine, so not 100% sure!

The one on the top also could be part of the heater control vent, actuates the door for warm air vs. cold air.


Does the vehicle have cruise control? The one on the bottom looks reminiscent of cruise control components I've seen.

Other than that, that stuff is and never was on either my '81 or '84, so maybe someone with your year may know.

 

Nope no cruise. My buddy said the same thing about the vent.

This is an xlt stripped down bronco. ha It has vinyl seats and floor and is your very base model. No bells or whistles on this thing...which I like.

 

Sounds about like mine. The biggest luxury mine came with was a vent.

Now that I think about it, I vaguely remember the round ball being a vacuum canister. It's purpose is to store excess vacuum to use when the engine is under load and not producing vacuum (ie. engine floored, vacuum needle drops to zero). It's necessary for later models that use vacuum for things such as vents/AC/heater controls.
Wasn't on early models because they used cables.

You won't really miss having it, except that in the winter, you may get a burst of cold air when you floor it since the vacuum won't be keeping the heater door open for a few moments.

 

Makes sense.

My buddy that has been helping me with this is working on a write-up with some questions. He is a more mechanic mindset than I am so I'll post it on here when he gets done.

 

Ok folks. Here is what my buddy who has been helping me wanted me to post. Your thoughts...



My apologies in advance for typing errors/things I forget to type….
Hi I am helping Arkdriver on the conversion. Here what has been done and noted.
1. Wiring harness was hooked up, found a few shorts so it has all been rewired so it has all new wiring for the system (from dizzy to ignition box), the adapter ends have all be checked and bad ones replaced.
2. New distributor (1981 model) (TDC set perfectly, retimed and reset multiple times just to make sure)
3. New ignition box/dura spark (for 1981 model)
4. New plug wires
5. New plugs a little dirty but run well
6. New carb (1981 model)
7. New manual choke conversion

Noted items
1. Prior to the full conversion there was a plastic “Y” connector for the vac line system. It broke and was never routed to the carb to our memory (it’s been a while).
2. The intake manifold has a screw in large metal fitting that has 4 or more lines coming off of it, that unit is good but some of the lines coming off it are either not hooked up because of number 1 above, or they were capped by us.
3. The egr is present and is functioning normally when pressed in at idle (it makes it die out as you know), it’s not to say it is not bad though.
4. From the egr going toward the carb and the wire harness, we found a small vac line that was unplugged, I think it came off the broken “Y” connector.
5. Brake vac lines and vac lines for the AC/Heating system I bet are out of place thus causing vac leaks.
6. The main thing that I need to know is the factory routing for the all the vac lines for all vac line systems, those that are not hooked to the carb.

The Running of the vehicle
1. With the air filter off (it’s all stock so re-burns are open, PVC is hooked up)
2. We didn’t check to charcoal canister (I’ll have to do that)
3. Vac advance off carb and plugged on both
4. Set at TDC, started at 6 BTDC
5. After it was warmed up timing was set between 9 to 11, it really liked 10.
6. Vac wouldn’t go any higher than 17 (tuned everything to get it higher but nothing, it held steady though)
7. So we are doing all the tuning—fine tuning the idle mixture and the throttle for the highest vac as “AbandonedBronco” mentioned.
8. The engine pretty smooth. I forgot my RPM gauge to see what RPM’s it was at, I have tuned a lot of motors and I bet money it wasn’t much off 700rpms, I’ll have bring my gauge to next time.
9. Well the engine was turned off. We started it again…It was very hard on the starter and wouldn’t turn over/locked up---it was having starter kick back!!! Fun!! So I have been there done that and knew right off that while Arkdriver was starting it I would deadvance the distributor and it would rotate and once started I would advance it back to where it like it (10 degrees).

This is what I/we need:
1. We have vac leaks in the system not related to lines that go to the carb. So can someone do a video sweep of their motor? I just need to see a factory motor and we can line it all up.
2. Once the vac leaks are taken care of, we should not have starter kick back due to over advancement, but with these broncos is there anything in the starting system that adds some type of initial electrical resistance at start up that would de-advance the distributor at start up so it turns over and quickly goes to proper timing? Some vehicles have them and I am not sure if this model does. And if so is it in the ignition wiring somewhere (I can’t remember the name of this resistor)

Other odds and ends:
The opening right behind the oil cap will suck air rather that push air (blowby) it get hooked up to the stock air filter houseing, the PVC valve is hooked up so I am guessing it is causing the suck as it is hooked to full vac.

After we tuned it we heard a hiss---it was two open vac lines off the A/C/heater system (I think) and one that looks like it coming off the egr. We hooked up the advance line and it worked good, we drove it a little and still heard other hissing… I hate vac systems…there everywhere on this thing…

Final thoughts:
With all the vac lines identified we should element that issue. After that we can retune it and identify anything missing. You can’t make it run right if your vac lines leak—been there done that over the years…

Please keep in mind I typed this fast so I may have errors and thing I forgot…
-Sparky

 

First off, there's one big thing to keep in mind. The engine is no longer stock. So, no vacuum diagram is going to match your current setup, and a pre-feedback engine vacuum setup isn't going to completely match yours. Various different components, such as that vacuum reservoir and the vacuum operated heater controls, were cable operated until '85 or '86, so they may not match either.

Not saying its difficult to get correct, but just cloning someone else's vacuum setup may not be the way to go.

One quick question, are you using the stock lines? Or have you replaced them with new rubber vacuum lines?


If it were mine, what I would do, is go over the engine with a fine toothed comb and cap off every vacuum port that isn't in use. Then connect the ones you know you need, especially the ones listed above (vacuum advance, PVC, brake booster). After you get the engine running smoothly, you can focus on getting the other ones hooked up.


That vacuum tree that comes out of the manifold is for options. Some used all the ports, some used a few, etc. It's there for whatever accessories may or may not need it. Don't think all of the ports need to be used for something.

Secondly, some of the components were for the feedback setup and will no longer be needed. An example would be that large cluster of vacuum solenoids on the rear of the valve cover. You can pretty much remove those and anything they go to.

Can you take a bunch of pictures of your engine bay? It'll help to see what's still there and what may need to be hooked up, as well as the ability to see what isn't needed or what can be capped off, or might be out of place.

 

Thanks for the reply AB!

We understand it's not stock and that some will need to be capped but several vac lines were/are out of order/broke prior to conversion and we wanted a baseline to work with. We can post some pics and a video soon.