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I have a very clean 1987 F-250 with the 460. I am posting here since the 87 was the last of the carbureted years and has more mechanical similarities to the Bullnose years. It was my grandfather's that I am trying to keep on the road. Now I reached a year when I wasn't supposed to have emissions on the truck anymore, but they changed the law the next year, so I need to keep the thermactor system going. I was eventually able to get it to pass emissions, so I am good on the tags for a year. Yet it was a bit of a pain. Well, I think I also found reasons why it was hard to tune the carburetor correctly. While I was taking the entire front assembly off, many of the black vacuum hoses were old and cracked; I can replace those, but one of the green, harder-plastic vacuum lines seems to have been cut by someone. The very reason I don't like anyone else working on this old of a truck. Does anyone have a source for these kinds of lines? If not, does anyone have any suggestions for a different type of line that would work? My second question is about the large silver up pipe coming from the passenger-side exhaust manifold. What is it for? It seems like it should be connected to the bottom of the inlet to the air cleaner, as I have seen a hose for sale for that position. Yet that round piece on the air cleaner, where a soft pipe should go, doesn't actually go through into the air cleaner inlet. I also suspect this is why I smell more exhaust in the last few years than I used to.
Cool! Apparently that stuff is pretty amazing. Look at all it can do:
For example, I often worry if my daughter's boyfriend is right for her. I will have to order this kit so I can stop worrying.
All seriousness aside, if you only need to re-establish that cut vacuum line, just slip some ordinary rubber vacuum line over the stub of the rigid line. At the other end, you can probably slip the rubber hose directly over the existing fitting.
My second question is about the large silver up pipe coming from the passenger-side exhaust manifold. What is it for? It seems like it should be connected to the bottom of the inlet to the air cleaner, as I have seen a hose for sale for that position. Yet that round piece on the air cleaner, where a soft pipe should go, doesn't actually go through into the air cleaner inlet. I also suspect this is why I smell more exhaust in the last few years than I used to.
There should be a flex duct between the elbow (at the exhaust manifold) and the opening on the bottom of the air cleaner snorkel.
Look inside the snorkel. There should be a flapper door at the hose connection, with a vacuum actuator on top. IIRC, the default position is closed to heat from the exhaust manifold. With the engine off, that is what you will find. That actuator is automatically controlled by a temp sensor in the air cleaner housing. The idea is to provide a constant air temperature to the carb inlet. This helps the air/fuel mixture from fluctuating wildly with temperature changes. It also helps reduce icing at the carb venturi.
This thread has some details about how this heated air intake works. There is some other material, and the subject engine was a 351W, but the general principles are the same:
Exhaust smell in the cab? Even if the heated air intake was jammed open, so it only drew air from under the hood (and not via the fresh air hose drawing from the front), any exhaust fumes present would be drawn into the engine and then back out the exhaust. The heated air intake shroud on the exhaust manifold? That should be totally sealed from exhaust fumes. Most likely you have an exhaust leak somewhere, and the fumes are getting drawn into the ductwork for the cabin heat/AC system. That air intake is in the cowl at the base of the windshield. Check the seal between the hood and cowl. While never intended as a perfect seal, it should keep most fumes from reaching the cabin air intake. And you may not have an exhaust leak per se. Might just be an oil leak hitting the exhaust somewhere, causing a burnt smell similar to exhaust.
In your picture above, is that a plastic Tyrap between the exhaust manifold and cylinder head? If so, snip that off because it will melt and make a nasty mess/smell.
if you only need to re-establish that cut vacuum line, just slip some ordinary rubber vacuum line over the stub of the rigid line. At the other end, you can probably slip the rubber hose directly over the existing fitting.
This works. Been there, done that. You can use regular small diameter rubber hose as a sleeve to splice the two ends back together. I believe the green line is for the EGR, with another green line that branches over to the EVAP purge valves.
Or, just get standard vacuum hose from the auto parts store.
Thank you, that link is definitely for the win. For now, I was able to buy a second-hand setup for the entire Thermactor system, which also included the fittings and lines I needed. But between you and another form, where someone showed that Rock Auto has the rubber elbows. I can remake any of the vacuum lines now!
There should be a flex duct between the elbow (at the exhaust manifold) and the opening on the bottom of the air cleaner snorkel.
Look inside the snorkel. There should be a flapper door at the hose connection, with a vacuum actuator on top. IIRC, the default position is closed to heat from the exhaust manifold. With the engine off, that is what you will find. That actuator is automatically controlled by a temp sensor in the air cleaner housing. The idea is to provide a constant air temperature to the carb inlet. This helps the air/fuel mixture from fluctuating wildly with temperature changes. It also helps reduce icing at the carb venturi.
This thread has some details about how this heated air intake works. There is some other material, and the subject engine was a 351W, but the general principles are the same:
Exhaust smell in the cab? Even if the heated air intake was jammed open, so it only drew air from under the hood (and not via the fresh air hose drawing from the front), any exhaust fumes present would be drawn into the engine and then back out the exhaust. The heated air intake shroud on the exhaust manifold? That should be totally sealed from exhaust fumes. Most likely you have an exhaust leak somewhere, and the fumes are getting drawn into the ductwork for the cabin heat/AC system. That air intake is in the cowl at the base of the windshield. Check the seal between the hood and cowl. While never intended as a perfect seal, it should keep most fumes from reaching the cabin air intake. And you may not have an exhaust leak per se. Might just be an oil leak hitting the exhaust somewhere, causing a burnt smell similar to exhaust.
In your picture above, is that a plastic Tyrap between the exhaust manifold and cylinder head? If so, snip that off because it will melt and make a nasty mess/smell.
Well, I learn something new on this thing every day, it seems. I always saw the inlet flap open when the truck was off. I just had no idea that there was a second flap at the bottom. When I had always looked before, I thought it was weird that it seemed just solid there, but had a place for that silver hose while browsing parts online. So thank you for the link and information. As for the exhaust fumes, I was just wondering, since I didn't have the aluminum hose that attaches to the heated air intake shroud, if that would be an issue. Does that silver elbow on the exhaust manifold not connect fully into the manifold, then? Is it just to direct heat from the manifold externally? I mean, an exhaust leak is likely since it's almost 40 years old now, and I have no idea if the gaskets have ever been replaced.
The plastic-looking piece between the cylinder head and manifold is the spark plug wire, right above the shield to protect it. Or do you mean the other black line farther to the left in the photo?
This works. Been there, done that. You can use regular small diameter rubber hose as a sleeve to splice the two ends back together. I believe the green line is for the EGR, with another green line that branches over to the EVAP purge valves.
Thankfully, I found a replacement one for sale. But yes, that would be a simple enough fix as well. As for all the vacuum routing on this thing, I still really have no idea where most of the lines go or what they do. Deciphering the vacuum routing diagram under the hood has a lot of abbreviations for what they are hooked to.
Cool! Apparently that stuff is pretty amazing. Look at all it can do:
For example, I often worry if my daughter's boyfriend is right for her. I will have to order this kit so I can stop worrying.
All seriousness aside, if you only need to re-establish that cut vacuum line, just slip some ordinary rubber vacuum line over the stub of the rigid line. At the other end, you can probably slip the rubber hose directly over the existing fitting.
I think some of my main goals with this truck is to keep is as OEM as possible since it still has under 80,000 miles and has sentimental value to me. If I just wanted it to work I would do as you suggested though.
Ha, as your your daughters boyfriend, well even if you wonder if he is right for her. Ususally kids don't listen it seems.
In your picture above, is that a plastic Tyrap between the exhaust manifold and cylinder head? If so, snip that off because it will melt and make a nasty mess/smell.
I think I see what you are talking about now....didn't even notice that till just now, It looks like a zip tie. I'll get it out tomorrow.
Does that silver elbow on the exhaust manifold not connect fully into the manifold, then? Is it just to direct heat from the manifold externally?
The silver elbow is part of an external shroud around the exhaust manifold. As long as the manifold is not leaking, no exhaust enters or passes through that shroud. All the shroud does is hold in the heat from the exhaust manifold to warm up the air being drawn into the carb.
The shroud is not a tight fit around the exhaust manifold. It is deliberately loose to allow airflow via the flex hose to the carb.
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