choke vacuum leak?
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Tuned
Joined: Jun 2010
Posts: 390
Likes: 5
choke vacuum leak?
The old 86 F150 4.9 (300) again ....
So the previous owner took off the automatic choke and put on a manual choke.
It is working fine.
When I was looking at the engine today, I heard a vacuum leak. Looking around I found that the leak was where the choke tube use to go into the carb (tube is long gone).
The engine has been running fine with this leak ... maybe a bit lean looking at the plugs but not bad.
I was about to plug the leak then I started thinking ... the carb is designed to have gas (exhaust) flowing into this hole. Maybe it works better with air flowing in (not sure what is really does in the carb).
Should I block if off or leave it leaking in air?
Thanks .... Mike
So the previous owner took off the automatic choke and put on a manual choke.
It is working fine.
When I was looking at the engine today, I heard a vacuum leak. Looking around I found that the leak was where the choke tube use to go into the carb (tube is long gone).
The engine has been running fine with this leak ... maybe a bit lean looking at the plugs but not bad.
I was about to plug the leak then I started thinking ... the carb is designed to have gas (exhaust) flowing into this hole. Maybe it works better with air flowing in (not sure what is really does in the carb).
Should I block if off or leave it leaking in air?
Thanks .... Mike
Lead Driver
Joined: Jul 2009
Posts: 6,477
Likes: 19
From: Sheffield, AL
Connect a rubber vacuum hose to the metal tube stub exiting the choke housing and the other end of the hose to the port located high on the carburetor [where the red original vacuum hose was connected which connected to the metal tube which connected to the exhaust manifold]. The air going into the choke housing will now be "clean/filtered" and will be the amount the engineers worked with when they calibrated the carburetor based on the designed vacuum leak which originally pulled in warmed air for the choke spring.
Thread Starter
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Tuned
Joined: Jun 2010
Posts: 390
Likes: 5
Fantastic!!!!!!!!!!
Once again, exactly what I needed to know!
I just got the new ignition on on the truck and I don't know how I didn't notice this before.
I realize vehicles are "engineered" to work a certain way and I am always afraid of doing more harm than good when I change things.
Thanks so very much!!!!!!!!!
Mike
I just got the new ignition on on the truck and I don't know how I didn't notice this before.
I realize vehicles are "engineered" to work a certain way and I am always afraid of doing more harm than good when I change things.
Thanks so very much!!!!!!!!!
Mike
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