What is supposed to be connected to the top nipple on this thing? Also is it possible to remove this thing and the hoses, looks terrible and is always in my way when I'm trying to work on the engine.

 

If you're not running a catalytic converter, or if you're running a modern one which doesn't require Air Injection, then you can remove the whole system. But don't throw it away. (It kinda looks like the one on Boss 429s?) Is the pump still there? Is the belt on it?

Definitely a vacuum hose is needed on that nipple. I think that that is a Diverter Valve.

Where do the output hoses lead? To the backs of the heads? Where ever those output hoses go, they slip onto metal at the other end. And at least on '80s-'90s vehicles, there is a check valve where the other end of the hose connects, so you can remove the hose, and not have an exhaust leak.
A picture from farther back would be good, because I'd need to see where those hoses all go. Probably one comes from a Bypass Valve, which is connected to the Thermactor (smog pump) output. And I'm guessing that one of the other two hoses goes to the rear of the cylinder heads, and the other goes back to the catalytic converter, Upstream and Downstream. It doesn't have individual brakeline-size lines running externally to the exhaust manifold (ports) does it?



So to describe the system, you've got the Thermactor/pump which feeds Secondary Air to the Bypass Valve. The BV either dumps the Secondary Air and blows it on the ground, or routes it to the Diverter Valve.
The DV sends the Secondary Air either Upstream to the exhaust ports, or Downstream to the catalytic converter.

The Bypass and Diverter Valves are controlled by vacuum - hence that nipple. And the vacuum is controlled by a Temperature Controlled Vacuum Switch which threads into the intake manifold or thermostat housing, and senses coolant temperature. There might be another CTVS for the distributor vacuum advance. The BV and DV are controlled by computer-controlled vacuum switches on my Mustang.

Is there (still?) a VECI label under your hood? It will list the plug gap and idle specs, as well as provide a vacuum diagram, in case you want to restore function to the system.

Wow, I really got to rambling...

 

The smog pump has been disconnected by PO, no belt on it anymore. One hose runs to the pump, the others go to the cylinder heads I believe (at least one does I'll have to go take a look to confirm). No VECI tag anymore, I did just receive the shop manual on CD today so I'll have to give that a read to figure out the original setup. Is it okay to hookup vacuum even though the smog pump is disconnected? Is this manifold vacuum or ported?

 

If you remove the divertor valve, you will have open exhaust under the hood that you will need to plug off.

 

If the belt isn't on the pump, then I wouldn't bother connecting any vacuum to the controls. Pretty sure it uses manifold vacuum exclusively, but the vacuum gets processed by temperature controlled valves, so that the system works properly whether the engine is hot or cold. I'm guessing that when it's cold, it sends the Thermactor air to the catalytic converter, and once it warms up, the air is sent to the heads/exhaust valves.


He might, I'm not sure though. I am sure that by the Fox Mustang days, that Upstream and Downstream tubes (where the metal hoses from the Diverter Valve go) have check valves on them, in case a hose splits or gets removed.

 

Yes there are check valves in the system, I meant if he removed the whole system. The diverter valve lets the air pump air go to atmosphere when decelerating to prevent backfire.

 

D5TZ-9B289-B .. Air By Pass Valve / Marked: D5TE-9B289-AB / Obsolete

1975/79 F100/150 302 A/T // 1975/77 Bronco 302 A/T

Upper pic:

 

Thanks for the information guys, I ran into a problem with this system tonight. When I tried to start it up with the hood open I noticed smoke so I stopped and realized that the passengers side check valve had broke off the metal tube that comes from the head. I'd love to just get rid of this whole setup can I plug the heads somehow? Here is a picture of where the tube connects to the head.

 

Okay so I unbolted the part from the head and it looks like the head itself is not threaded at all, the metal pipe leading up to the check valve and the piece in the head are all one unit with a long bolt that goes through the center to hold it in place. Is there any way to plug this?

 

Hmm. The Upstream Air Tube on 5.0s is a little different, and some have cut the ends off of the tube, and bolted them backwards to the head! So that the closed side of the Air Tube 'end' is covering the hole in the cylinder head. On the old small blocks you can also thread a spark plug into those holes. But the holes are on the backs (and fronts) of the heads.

Are you saying that the bolt hole is not the air passage? If it's not, then the fix is bolting down something which covers the hole.

Maybe clean the hole real good and see if you don't uncover any threads. Even if you don't, you could still tap them for a plug or bolt. I don't think I'd be scared to do this on the truck, as I would start up the engine before putting in the plugs/bolts, and hopefully expel any shavings.
Can you post a pic of the head with the Air Tube removed?

I actually went the other way here, and used a hand drill on some junkyard-picked GT40P heads, to drill thermactor passages back to above the rearmost exhaust ports. I then drilled up through the tops of the ports to meet the passage. Also drilled and tapped bolt holes for the (one-piece) Upstream Air Tube. I bolted the heads onto my Mustang, and sure enough got all elevens when I scanned the EEC. No error codes, 44 and 94, which denote "no Upstream Air detected."













I never get tired of bragging about it either...

 

Probably hard to tell from my picture but the port in the head is on the side not the back like I keep seeing everywhere when trying to find out how others have done this. There is one on the front passengers side head and one on the back of the drivers side but both are on the side of the head. The bolt goes through the center of that flared fitting to hold it in the head but because of the size of the fitting internally the air can easily flow past the bolt and into the tube. For now I smashed the end of the tube with a hammer and vice to close it up but I need a cleaner longer term solution. I can't understand why I can't find any information on this setup, everything I can find has these on the back of the heads not the side. I need one of the flared fittings without the tube but it doesn't appear those exist. I could tap the holes to thread in something but if there is a part available to plug it without modifying the heads I would prefer that.

 

Naw, I noticed that they are on the sides, and I'd never seen that before. With what you've got, at least you can't put your heads on the wrong sides of the block. But folks have run into trouble when R&R'ing small block heads which have had their Thermactor holes plugged - because the passage starts life as an accessory bolt hole for the front of the engine...

I'm thinking you can cap the passage with a large washer, though you might need a shorter bolt - or else a huge stack of washers... You say the passage is one hole next to the bolt hole?

 

Yeah that is what I'm going to try tomorrow, see what I can find at the hardware store and use a washer with a shorter bolt and some ultra copper gasket maker between the washer and the head. Surprised no one makes an aftermarket part to plug them but I guess this must not be a common setup since I couldn't find much of anything about it googling for information.

 

Wait and see if anyone else chimes in, as I'm sure a few guys here have been exactly where you are, and will know the best parts for that job.

 

Bump, anyone else ran into this and know of a good solution or somewhere to find a replacement part?