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Hi all,
I replaced the thermostat on my 86 F250, 460 engine, and when I was putting things back together I noticed a segment of tubing going from the distributor to the carburetor that was burnt in the middle. It broke when I examined it. I need to know what it is for and how to replace it. The tubing is brittle and has a very small inside diameter, like less than 1/8 inch.
There is a similar broken piece of tubing connected to some sort of device mounted above the belts. The other end of the tubing isn't attached to anything, it also looks burnt. I'm wondering what it's supposed to connect to.
Dont know what that can is but you can cut the plastic tubing to good tubing that isn't deformed and slide some 5/32 rubber vacuum hose over it to reconnct it. I believe its 5/32 if I remember right.
Those black cans are the diverter valves for the air injection systtem.
One is for the thermactor ports in the back of the heads, the other for the 'log' above each exhaust manifold.
The one from the carb to the distributor is for the timing vacuum advance. The others are for the air pump system and diverter valves. Take a look on the underside of the hood or near the radiator support for an emissions sticker, there is a vaccum diagram from the factory there if it is not worn or gone.
Those black cans are the diverter valves for the air injection systtem.
One is for the thermactor ports in the back of the heads, the other for the 'log' above each exhaust manifold.
I can only find one of the black cans. Are you sure there are 2? Any idea what the front one is supposed to connect to? Haven't looked for the diagram yet.
Dont know what that can is but you can cut the plastic tubing to good tubing that isn't deformed and slide some 5/32 rubber vacuum hose over it to reconnct it. I believe its 5/32 if I remember right.
I can only find one of the black cans. Are you sure there are 2? Any idea what the front one is supposed to connect to? Haven't looked for the diagram yet.
You have two AIR pumps, right?
The front diverter valve should be on a bracket attached to the pump bracket casting directly behind the upper pump.
Maybe things are different for trucks over 9,200 gvw?
I'm sorry but I don't remember for sure.
I have posted pic's of my routing diagram here on the forum before.
The vacuum control systems on these trucks are, to me anyway, complex and there is no guarantee that your vacuum lines haven't been modified after all these years.
For example, the vacuum line going from your carb to your distributor appears to be ported vacuum whereas the vacuum to the distributor on mine comes from the manifold through a thermal vacuum switch mounted on the thermostat housing neck.
Anyway, you should have two air pumps driven off the alternator and two diverter valves, one up front and the other back toward the fire wall on the passenger side, and each of the diverter valves should have two vacuum lines running to them. You might take a look at the vacuum lines attached to the rear diverter valve to get an idea how the front valve should look.
The vacuum control systems on these trucks are, to me anyway, complex and there is no guarantee that your vacuum lines haven't been modified after all these years.
For example, the vacuum line going from your carb to your distributor appears to be ported vacuum whereas the vacuum to the distributor on mine comes from the manifold through a thermal vacuum switch mounted on the thermostat housing neck.
Anyway, you should have two air pumps driven off the alternator and two diverter valves, one up front and the other back toward the fire wall on the passenger side, and each of the diverter valves should have two vacuum lines running to them. You might take a look at the vacuum lines attached to the rear diverter valve to get an idea how the front valve should look.
Also depends on vehicles my ford truck the 302 runs on manifold vacuum where as my Mercury the 351w runs on ported vacuum and the factory shop manual set I have says that is correct. Which makes sense when you are idling you really don't need to advance your timing only when you start racing the engine up. I might go ported on my truck when I build the engine.
But you are right that vacuum lines can and do get modified and swapped around I had one that bunch of vacuum lines had nails and screws in them as they didn't want to fix them just stuffed a nail in the broken line.
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