I'm finally getting around to a carb and intake swap on my truck. It's an '86 F250 with the 351w, HO, and I think C6 transmission. It's 4x4 with a long bed and a plow setup. I bought it a couple years ago and it didn't run well enough to use regularly. My mechanic suggested that I get rid of that old stock Holley, I guess they weren't very good to begin with. So after a lot of reading on this forum and others, I decided to swap it with an Edelbrock 1406. I will also be installing a 2181 intake manifold from Edelbrock.

While I usually maintain my own cars and my old motorcycle, I don't know much about trucks in general, especially 80s trucks with their unbelievable rats nest of emissions wiring and hoses. That is all coming off. Somebody has already tossed the smog pump, and there are a bunch of capped off vacuum lines. It's a horrible mess, and I don't even know what most of it is.

When I started researching this, I thought "gee I can figure out vacuum hoses." But I wasn't expecting all that crap to have so many wires running everywhere. We don't have emissions testing for rigs this old, and really I'm not going to use it much. I commute by car or motorcycle, the truck is just for errands and picking up projects. Haven't figured it all out yet but I know I need vacuum for the brake booster, distributor advance, pcv, and maybe something on the dash.
Where is the current PCV valve on these?


For the edelbrock swap, I will be eliminating much of that mess. But before I begin removing things, I am hoping to understand what some of it is so I don't cut or remove anything I'll need later.

First off, what is this thing in the yellow circle? There are two, looks like one should be mounted to each valve cover (I know the one on the right isn't, but should be on the right valve cover I believe).
And, can you see the cable end I circled in green? I'm guessing that is the choke cable?



Next, the item in the green circle I believe is in line with the hose to the brake booster. What is it?
The thing circled in yellow, there are two of them.
And the thing circled in blue, is that my temp gauge sender? Because the temp gauge does not seem to work.


Old carb, the red arrow points to the throttle cable and the green one points to the trans kick down linkage? I ask because there is a linkage kit I need to get from edelbrock for that, trying to envision how it all hooks up.


Finally, what is this bank of red wires?




One more thing, do these trucks have any electric trickery with the ignition? Or is it an old school cap and rotor, points, etc? This looks unfamiliar to me:




Thanks everyone, and if you made it this far then good on ya! This will take me a while, I am juggling many projects, but I'll be starting this week and would love any help you all can offer!

 

The thing in the yellow circle is a EGR load control WOT valve. I see it has orange lines going to it. If you can make out your vacuum diagram on the radiator, see if orange is the EGR system. If it is, then that is what that valve is in the yellow circle. It can leave.

These trucks did not have a choke cable. But someone may have added one. If you have a choke cable mounted under the dash, then that is what it most likely is. in the green circle.

 

Are you sure that line in the green circle goes to the brake booster? That is the front of the engine. The brake booster is always fed from the rear of the engine behind the carb on any engine I have messed with. But someone could have hooked it up wrong also.

The yellow and blue circled items look like temperature controlled vacuum valves. They screw into the water passage and block or pass vacuum when the water gets to a set temperature. All that can leave also.

 

That is the kickdown rod for the trans. Play with the throttle a little bit before you take it loose from the original carb. You will see it does nothing during most of the throttle travel, but when you get near wide open, the linkage hits the rod and starts moving it. When you mash the throttle to the floor, it makes the trans downshift to 2nd gear. Your new throttle kit will have to be adjusted so it works the same. You will have to adjust the throttle on the new carb so when someone presses the pedal all the way to the floor, the carb linkage is wide open, and then you can adjust the trans kick down so it activates at the upper end of the travel.

 

I think red is manifold vacuum. That looks like a manifold that is distributing manifold vacuum to different components on the engine. Sort of a "vacuum tree". You will have to check your diagram, it is colored. Believe it or not there was a method to this madness.

 

Ford did have distributor trickery. But lucky for you, your engine is a 4v HO engine. It has the standard duraspark II distributor with the duraspark II ignition box mounted over on the inner fender.

 

The Edelbrock kit for the trans. kick-down rod sucks. I bought the kit but didn't use it because the hook up is wonky. I just left off the kick-down rod. Since I converted from stick to auto (another story) I used a Hurst Pro-matic 2 floor shifter. If I need to down shift to accelerate, I just slap the shifter into 2nd.
If you want my downshift kit you let me know.

 

Thanks a million Franklin! That is a huge help.

My Edelbrock 2181 intake has no provisions for EGR, so I will remove all that I guess.
I will double check that cable. The Edelbrock 1406 I ordered has an electric choke.

I will double check that vacuum hose from the brake booster. It's all so tangled in there, I could be wrong.

Saving this for when I get to the carb. Very helpful, thank you!

Ok, so I think what I assumed were wires are actually very small vacuum lines? That eases my mind as I was afraid this truck might have a computer somewhere that would go nuts if I started cutting stuff out!

Cool, I googled Duraspark II, makes sense now. It's just an old school distributor with elec. ignition instead of points. Is there any other computer crap associated besides the ignition module?

 

Thanks I will keep that in mind.

 

Going forward, I know I need vacuum for the PCV, distributor advance, brake booster, and maybe something on the dash. I am also reading online about the transmission vacuum module. Does this get its vacuum from the intake manifold as well? I need to plumb it in to my 2181 Edelbrock intake?

 

Yes to the intake.
Now your transmission may not have vacuum as it has the kick down rod but I could be wrong.
The dash vacuum is for HVAC. If you have AC vacuum is what works the doors to switch from defrost / vents / floor.
Dave ----

 

If the trans. is a C-6, it does have a vacuum controlled modulator; one single line from manifold vacuum source to the trans. modulator valve.

 

Thanks! I will try to trace it later today.

I'm thinking of getting new valve covers just to clean up the top of the engine. Do I get a pcv valve that goes on the valve cover? I'm not sure where the one on my truck currently is.

 

I consider the Holley and Motorcraft 2100/2150 carbs superior to the Edlebrock. Sounds like you already have the Edlebrock, so that's fine.

--You will notice a vacuum tree on the passenger-ish side of the firewall. That will need to be left in place--it controls the HVAC and transmission. This gets full manifold vac.
--PCV goes from either valve cover into carb/spacer. Breather must be installed in opposite valve cover. For best results it should be routed into air cleaner assembly via 11/32 or 5/8 hose. Use push-in breather if original air cleaner assembly gone.
--Distributor vac advance goes to Carb port above throttle plates
--EGR goes to coolant temp switch (yellow thing in pic) then to EGR port on carb below throttle plates

 

I would be careful getting aftermarket valve covers. They all will have a hole for the PCV valve, and some of them do not have very good oil baffles in them for the PCV valve. The PCV valve is continually sucking the bad stuff out of the engine when it's running, but there needs be a shield or baffle under it so it doesn't suck any oil in it that is splashing around under there when the engine is running. I have had cheap valve covers before, and the engine actually used oil till I figured out what was going on. I am assuming a quality valve cover will have a good baffle, but it's hard to beat the factory cover baffles that come in those.

And jackie was right, if no one has messed with it, you should have a small plastic tree mounted on the firewall above the engine. It will have one coming off it going to the pass side to feed the HVAC controls. Another going down to the transmisson. And another going to the engine to get manifold vacuum.

You will need a large port on the back of the manifold for the brake booster. You can see if you can rob something off the original manifold or you can use pipe fittings from the store to get it going.

Your carb will usually have large port for the PCV valve. Read the instructions to find the proper port. Try to use that port, it will let the gases from the PCV valve go in very near the base of the carb through a passageway, and this lets the gases get mixed equally to all the cylinders. If you put the PCV valve on the back of the manifold, the rear cylinders can get too much of it and it can cause the engine to run a little rough.

For the small vacuum line that feeds the plastic firewall manifold, you can see what you have left, sometimes the carb will have a manifold vacuum port and you can use that. I highly recommend you use the ported vacuum port on the carb for the distributor. It will not have vacuum at idle, only when you rev the engine.