I have an assortment of 5.0 & 5.8 throttle bodies and have been looking at them trying to decide which to use. They seem to be the same size but the vacuum line setups vary.

One TB has a single kinda large vacuum inlet on the left side, set at an angle between the barrels, and it's vacuum line is controlled by an electrically activated valve located between the TB and the charcoal Evac canister. This inlet has a passage that runs through the TB and ends in the IAC cavity, where it has access to the two large IAC holes in the TB. One for each barrel.

Another TB does not have the kinda large inlet but has two smaller inlets on the opposite side of the TB, above and below the IAC. These two simply 'Y' together into one line that runs to the Evac canister and there is no control valve. These two inlets are quite a bit smaller than the single one, are drilled straight into each barrel, and will apparently operate whenever the engine is running.

A third TB has all three. One large inlet controlled with the Evac Valve and the two smaller ones with no valve. They are arranged so that the two smaller ones again 'Y' together and are 'straight-wired' to the charcoal can with a single line. But there is a 'T' in that single line and it branches off to an Evac valve, which in turn connects to the larger inlet. Combining the designs of the previous two TBs. So in operation it appears that the two smaller inlets will put a slight vacuum on that canister whenever the motor is running but the computer (I assume) has the option of adding additional vacuum to that canister by opening the Evac valve. Which would seem to massively add to the vacuum put on that canister when open.

I'm guess I'm going to use the last one, which seems the most versatile, and use all the ports but it is the most oxidized of the bunch and the ends of the water inlet/outlet tubes are rotted away. Like I said, unless there's a good reason not to, I'm just going to cut the water lines flush and plug the holes. The rest is just a matter of cleaning and wire brushing.

Rob

 

Does whatever vehicle this is gong on have the ability to control a canister purge solenoid? If not then there's no point putting one on there.

 

It does. The original 5.0 had the single kinda large port and not the other two. So the wiring is there for the purge valve. I was wondering about codes.

The TB that has only the two smaller inlets has relatively intact water pipes and is generally in better shape and I had considered using it but was worried about computer issues and also was unsure if those small inlets would be adequate. I had thought to maybe use the purge valve inline with those small inlets alone, thus solving the computer problem but not sure about the vacuum capacity.

Rob

 

I say use the TB that's in the best shape regardles how it's setup. The computer simply opens and closes the solenoid.. it doesn't know how much vapor is passed so it doesn't matter what size the ports on the TB are or what size the vacuum line is. If you simply want to avoid codes you could even just plug a solenoid into the electrcial connector with no vacuum lines on it and just attach the canister directly to the TB, though that is a little silly if the valve is there and it works correctly.

 

I tend to agree with you.

As long as it vents the tank properly, I guess.

It appears that Ford increased the venting capacity as time went on. My bros '90 has only the small inlets and no valving. The '92 has the larger single inlet with the valve (which means there would be no venting until the valve was activated). My Dad's '93 has all three inlets as I described. And the raggedy '95 also has all three. And the one with two inlets that's in pretty good shape is from an '89, if I remember right.

One thing that may help is that I removed the mid fuel tank completely and installed a single 32 gal Bronco tank in the rear in place of the original 19 gal. So there is only one tank to vent.

I guess I'll try it with the valve inline with the two small inlets and see what happens.

Rob

 

After cleaning the baked on gunk inside the barrels and on the butterflyes, I discovered another difference among them. There are two types of butterfly, type 'A' and type 'B', (stamped right on the butterfly). Type 'A' has a 1/16" or so hole dilled in each throttle plate and is in the TBs that have three inlets and the TBs that have the single kinda large inlet. Type 'B' has no holes drilled in the butterflyes and is found in the TBs that have the two small inlets.

I have no idea why those are different. The ones with the holes would seem to negate or diminish the ability of the IAC to control idle air but maybe that's why they do it.

In any case, I think I'm going to have to use the raggedy 3 inlet TB or one that has only the single inlet, both of which have the butterfly holes, as I'm sure that will affect idle quality.

Maybe I can cut those rotten water pipes off and tap the holes for some small elbow fittings.

 

My truck has the two smaller vacuum ports and non-drilled butterflies. It has a plate between the IAC and the throttle body with adjustable set screws to adjust the amount of air bypassed at idle irrespective of IAC demand, which has the same effect as the drilled holes in the butterflies. Did any of the throttle bodies you have come with this adjusting plate/IAC spacer?

 

Sorry to take so long to reply, my wife dragged me off on vacation and I'm just now getting back to my truck.

No, I don't recall any plate such as you describe, but I'll check my bro's '90 as it's the oldest one I have access to (the '89 is in the great junkyard in the sky). I know the '92, '93, and '95 do not have such a plate.

I did manage to get the '95 TB cleaned and painted and it's now in pretty good shape so am going to use it, I guess, and go with the three vac line setup.

Seeing all that gunk has made me want to get rid of the EGR valve, though. Got to make me a blockoff plate for the intake and plug the header outlet. Saw an EGR eliminator doodad for twenty bucks somewhere to stop any codes.

Rob