79 400m runing right issues
Freshman User
Joined: Nov 2003
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If the idle mixture screws don't seem to do much, then you are probably idling on the main circuits in the carb because your idle screw is in too far. This could easily be due to a vacuum leak. Did you have any backfires? I had a backfire blow out an intake gasket on two different cylinders. The gasket was blown out into the lifter galley. I've also had troubles with some gaskets slipping when I put the intake manifold back on if I didn't use enough gasket tack to keep it in place during the re-assembly.
I have also had trouble with a vacuum leak around the base of the vacuum tree where it screws into the manifold. Being in the back, behind the carb and around the A/C box (if you have AC), it is easy to overlook. Spray some starting fuid there with the engine running and see if it smooths out any.
Good Luck!
I have also had trouble with a vacuum leak around the base of the vacuum tree where it screws into the manifold. Being in the back, behind the carb and around the A/C box (if you have AC), it is easy to overlook. Spray some starting fuid there with the engine running and see if it smooths out any.
Good Luck!
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Senior User
Joined: Nov 2005
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From: belton mo
yea ive done the wd40 around the intake no leaks there.. and i guess there could be some leaks within all the hoses but i dont have the tree in the back the guy who removed all the egr crap put a thread in with a nipple i wanna call it and put the brake booster on it.. and the tranny vaccum on the big port on the back bottom of the carb which i thought was supposed to go to the top of the valve cover?.. its been a long time since i have worked on an older ford. suck in the new age . 
Elder User
Joined: Feb 2008
Posts: 999
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From: Davison, Mi.
The transmission modulator vacuum line taps into the same source of vacuum as the brake booster's. It gets full time access to manifold vacuum.
And yes the big vacuum line on the back of the carb is reserved for the PCV system.
Sounds like you have a DAPO.
And yes the big vacuum line on the back of the carb is reserved for the PCV system.
Sounds like you have a DAPO.
Elder User
Joined: Feb 2008
Posts: 999
Likes: 1
From: Davison, Mi.
Nope, it won't hurt anything and engines run well without PCV systems, but the fumes are noxious. Ok on a race vehicle but it sucks without one on a street machine.
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Senior User
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From: belton mo
Its a little late now But just so everyone knows i found out what my problem was the previous owner had ran it without the headers for about 2 weeks. so It cracked and screwed the valves all up.. 
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