Intake Manifold Lines
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Intake Manifold Lines
Was changin out the fuel filter today, when I took it off I noticed a line directly under the filter that had been cut off. I had never noticed it before since the filter was in the way. What is this, where should it go, do I need it? I'll post a pic if necessary.
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I should have posted that sorry, 1977 F150 400 C6 2WD. What did it use to hook up to? And what's with the empty threaded hole?
MSEE
Joined: Apr 2004
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From: Austin, TX
400 would be a dry manifold, so a vacuum tap is the only thing it could be. It's hard to say what it would have gone too; looks like a quarter inch ID so I would guess transmission modulator or heater controls maybe. The threaded hole is a mounting boss to mount an accessory bracket.
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MSEE
Joined: Apr 2004
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From: Austin, TX
I can't really answer that without knowing what vacuum accessories are missing from your truck, if any. A lot of times those came from the factory plugged; a previous owner probably put the hose there for some unknown reason. If you're not having any problems, just plug it and you should be fine.
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Postmaster
Joined: Jul 2001
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From: MD
Start the truck and put a finger over that hose. If you feel sucking, it's the front manifold vacuum source.
Some emissions calibrations use the front manifold vacuum source, some don't. That's why you see some with a nipple, some without. Mine has a nipple as my emissions diagram shows it was used for the vacuum reservoir by the main battery tray.
Since my vacuum routing is FUBAR, that hole was plugged with a vacuum cap. I use that source to hook up my vacuum gauge for diagnosing.
Some emissions calibrations use the front manifold vacuum source, some don't. That's why you see some with a nipple, some without. Mine has a nipple as my emissions diagram shows it was used for the vacuum reservoir by the main battery tray.
Since my vacuum routing is FUBAR, that hole was plugged with a vacuum cap. I use that source to hook up my vacuum gauge for diagnosing.
Postmaster
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From: MD
You can even use a bolt. But I'd just use a vacuum cap, so you can have easy access for a vacuum gauge whenever you need it.