Help with bucking bronco!
Thread Starter
Le Mans Master
Joined: Mar 2001
Posts: 6,640
Likes: 287
From: Ann Arbor Michigan
Help with bucking bronco!
My 78' 4 speed has started bucking during acceleration. Worst at part throttle. Lars just rebuilt the Q-Jet (it did it before he rebuilt it too). I have installed the Lars recommended vacuum advance and set timing per his paper. Still does it. I removed my MSD distributor and box and installed the bone stock 78' HEI. Still does it. It idles fine but seems to misfire during off idle light load. I have not touched the carb since Lars rebuilt it (though it is tempting). Compression is 160-170 on all cylinders. Installed new plugs also. It has good power once it gets past the bucking. Where do I go from here?
Thread Starter
Le Mans Master
Joined: Mar 2001
Posts: 6,640
Likes: 287
From: Ann Arbor Michigan
Thread Starter
Le Mans Master
Joined: Mar 2001
Posts: 6,640
Likes: 287
From: Ann Arbor Michigan
Le Mans Master
Joined: Jan 2006
Posts: 9,192
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From: Boca Raton Florida
Mine gets a ground for the distributor thru the harness. The ground and power come in thru 2 different connectors. Stick a test light on the distributor and wiggle the wires around.
Thread Starter
Le Mans Master
Joined: Mar 2001
Posts: 6,640
Likes: 287
From: Ann Arbor Michigan
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Thread Starter
Le Mans Master
Joined: Mar 2001
Posts: 6,640
Likes: 287
From: Ann Arbor Michigan
Good point, tunnel vision I guess. If I had a fuel starvation problem wouldn't I see a drop in fuel pressure? I have an electric pressure gage installed and it stays right on 7 PSI. What would be the best way to trouble shoot the fuel system without just changing parts?
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
It stays at 7psi when it's at idle or when you just rev the engine a tad with the linkage. What does it do under load when you are at half throttle? If you have an auto. tranny, have someone sit in the car with it in "Drive", brakes applied and rev it up a bit...then see what the fuel pressure is. I'm not sure what you do if you have a stick.
Thread Starter
Le Mans Master
Joined: Mar 2001
Posts: 6,640
Likes: 287
From: Ann Arbor Michigan
Thread Starter
Le Mans Master
Joined: Mar 2001
Posts: 6,640
Likes: 287
From: Ann Arbor Michigan
Thread Starter
Le Mans Master
Joined: Mar 2001
Posts: 6,640
Likes: 287
From: Ann Arbor Michigan
Race Director
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From: Dayton, Ohio
Race Director
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From: Florida
You can use a 3/8 stainless allen set screw. Be carefull when you thread the hole, use a starter tap and just thread deep enough so it will act as a pipe thread.
The early form of apt in 75 cannot be done with this method. It is a different style apt. You need a carb that has an aluminum plug on top of the fuel bowl.
Pictured also is an adjustment tool you must make.
The early form of apt in 75 cannot be done with this method. It is a different style apt. You need a carb that has an aluminum plug on top of the fuel bowl.
Pictured also is an adjustment tool you must make.