Carburetor running rich
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Mountain Pass
Joined: Nov 2019
Posts: 139
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From: California
Carburetor running rich
Finally got my Rig going but it's running rich now I have never really messed with carburetor. 1978 f100 Ranger 302 holley carb 2 barrel avenger any pointers on how to adjust would be appreciated thanks
Lead Driver
Joined: Oct 2018
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Running rich ? idles rich? plugs are dark ?
First make sure your choke is opening all the way. check your float level if it has windows. set your idle mixture then check your vacuum reading. you may have the wrong power valve or a bad one. if that all checks out then it might need jets.
First make sure your choke is opening all the way. check your float level if it has windows. set your idle mixture then check your vacuum reading. you may have the wrong power valve or a bad one. if that all checks out then it might need jets.
Mountain Pass
Joined: Nov 2022
Posts: 226
Likes: 83
From: South East Kansas
Holley and Ford carbs are famous for blown power valves. Alcohol based fuels, are hard on rubber that make up the parts in these carbs.
Many times one good back fire, through the carb, will damage a power valve, so, take care to make sure the choke is working properly, and dont crowd it, when its cold, to help avoid kick backs.
Provided the choke is open, and the float level is right, i would take a look at the power valve. A couple of tests that can be used to figure out if a power valve is good, is to close the idle mixture screws, and if there is no affect on the idle, the valve is not good. Also if the float bowl is dry or low, after sitting over night, the valve is leaking. A difficult starting warm engine, after sitting for a few minutes, can also indicate a leaking valve.
Regards, Brad
Many times one good back fire, through the carb, will damage a power valve, so, take care to make sure the choke is working properly, and dont crowd it, when its cold, to help avoid kick backs.
Provided the choke is open, and the float level is right, i would take a look at the power valve. A couple of tests that can be used to figure out if a power valve is good, is to close the idle mixture screws, and if there is no affect on the idle, the valve is not good. Also if the float bowl is dry or low, after sitting over night, the valve is leaking. A difficult starting warm engine, after sitting for a few minutes, can also indicate a leaking valve.
Regards, Brad
Hotshot
Joined: Feb 2004
Posts: 10,808
Likes: 2,604
From: The Shenandoah Valley
Yeah, if the power valve leaks through the rubber diaphragm, intake vacuum that normally just opens and closes it then pulls fuel through at a good rate, rich. One back fire will do it.
I once read an article on drilling the base plate portion of the power valve passage just enough to accept a small ball point pen like spring and steel ball, then if a backfire did go boom, the ball gets blown upwards against the normal size portion to block the passage. Don't drill the gasket and it'll help seal the ball. Normal vacuum pulls the ball down on the spring away from the gasket hole, it blocks nothing then. Holley started adding the feature long ago but a year or more after I read about it in HRM.
I once read an article on drilling the base plate portion of the power valve passage just enough to accept a small ball point pen like spring and steel ball, then if a backfire did go boom, the ball gets blown upwards against the normal size portion to block the passage. Don't drill the gasket and it'll help seal the ball. Normal vacuum pulls the ball down on the spring away from the gasket hole, it blocks nothing then. Holley started adding the feature long ago but a year or more after I read about it in HRM.
Lead Driver
Joined: Oct 2018
Posts: 7,877
Likes: 2,365
Starting in the mid 90's Holley put a check ball in that eliminates most blown power valve problems. it sounds like the OP has a newer carb than that. but it's still a possibility the valve is bad of course. .
Hotshot
Joined: Feb 2004
Posts: 10,808
Likes: 2,604
From: The Shenandoah Valley
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