too rich?
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too rich?
it's an 86 F150 351W. it has a Holley 650 Street Avenger, Dart Windsor heads, Performer intake, 160* thermostat, headers, and true duals that dump out Flowmaster 40s. i believe i'm getting too much fuel or not enough spark. the DuraSpark box, coil, wires, cap, rotor, and plugs are all new. my brother has been borrowing the truck while his jeep is in the shop. he only drives about a mile to work, then a mile back home. it runs horribly like this. it runs rough for a while after start up and blows some black smoke. after driving it for a while, it stops the smoking and runs great. it seems like the short trips are fouling the plugs, but getting it good and hot fixes everything. i still think it's running too rich. i'm no carb expert, so any help would be greatly appreciated. it also idles really high, like 1600-2000rpm.
different plugs, higher thermostat, better tuned carb, ... ?
thanks!
different plugs, higher thermostat, better tuned carb, ... ?
thanks!
Senior User
Joined: Sep 2005
Posts: 252
Likes: 0
From: Illinois
Originally Posted by jbirdsvt
it's an 86 F150 351W. it has a Holley 650 Street Avenger, Dart Windsor heads, Performer intake, 160* thermostat, headers, and true duals that dump out Flowmaster 40s. i believe i'm getting too much fuel or not enough spark. the DuraSpark box, coil, wires, cap, rotor, and plugs are all new. my brother has been borrowing the truck while his jeep is in the shop. he only drives about a mile to work, then a mile back home. it runs horribly like this. it runs rough for a while after start up and blows some black smoke. after driving it for a while, it stops the smoking and runs great. it seems like the short trips are fouling the plugs, but getting it good and hot fixes everything. i still think it's running too rich. i'm no carb expert, so any help would be greatly appreciated. it also idles really high, like 1600-2000rpm.
different plugs, higher thermostat, better tuned carb, ... ?
thanks!
different plugs, higher thermostat, better tuned carb, ... ?
thanks!
Does the engine continue to idle fast after it is fully warmed up? If so, you may have a choke problem that would also contribute to a rich condition.
Take off your air cleaner and observe the choke blade as the engine warms up. The choke blade should be standing straight up and down when the engine is warm. If it's not, the engine is being supplied with more fuel than it needs and since the the choke is connected to a fast idle cam, it will hold the engine at a higher idle.
Fleet Owner
Joined: Sep 2005
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From: Lake Tahoe, Nevada
Judging from all the mods you describe, I'm guessing the heat stove, hot air pickup off the manifold to the aircleaner has been eliminated. If so you will need to get that back in place. Also, scrap the 160 stat in favor of a 190-195degree stat.
Check the plugs for application, you may be a heat range too cold.
Check the plugs for application, you may be a heat range too cold.
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i was wondering if the plugs might be a heat range too cold. given that i don't have the stock heads, do you know a good place to check for the right plugs? i've emailed Dart, but to no avail.
to your response, Neb, how do i go about adjusting that choke. the carb that's on there has an electric choke, but has never been hooked up. even after the engine is up to operating temp it does still idle high. even after thrashing it all day in the woods, if put in park, it still idles just as high as the first time i started it. i was also wondering if the cam would make a difference in idle speed. i failed to mention that it has a Comp Cams cam, but i'm unsure of what the specs on it means. i have the spec sheet on the entire build if that would help. this engine was built from the bottom end up at a performance shop before i bought the truck.
to your response, Neb, how do i go about adjusting that choke. the carb that's on there has an electric choke, but has never been hooked up. even after the engine is up to operating temp it does still idle high. even after thrashing it all day in the woods, if put in park, it still idles just as high as the first time i started it. i was also wondering if the cam would make a difference in idle speed. i failed to mention that it has a Comp Cams cam, but i'm unsure of what the specs on it means. i have the spec sheet on the entire build if that would help. this engine was built from the bottom end up at a performance shop before i bought the truck.
Senior User
Joined: Sep 2005
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From: Illinois
As far as the choke goes, the first thing to do is to get 12 volts to it. The wire should have power on it only while the key is on. Your truck may have been fuel injected originally so you might have to run a wire specifically for the choke.
The important thing to remember is that the choke needs to be fully open when the engine is at operating temp.
Regarding adjustments, well, if you are idling at 1600 RPMs, that's a little fast for high idle but not out of line.
Also, when the engine is cold and not running, the choke blade should be fully closed. If it isn't just tap the throttle and it should snap closed with spring pressure. Watch the choke blade when the engine first starts... it should open slightly. There is an adjustment for that but, you'll need to consult a Holley manual or guru to find the exact measurement.
I wouldn't recommend driving your truck the way it is right now. Get your choke working then come back and let us know if you need anything else.
The important thing to remember is that the choke needs to be fully open when the engine is at operating temp.
Regarding adjustments, well, if you are idling at 1600 RPMs, that's a little fast for high idle but not out of line.
Also, when the engine is cold and not running, the choke blade should be fully closed. If it isn't just tap the throttle and it should snap closed with spring pressure. Watch the choke blade when the engine first starts... it should open slightly. There is an adjustment for that but, you'll need to consult a Holley manual or guru to find the exact measurement.
I wouldn't recommend driving your truck the way it is right now. Get your choke working then come back and let us know if you need anything else.
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From: Illinois
Originally Posted by Bdox
Do not tap into your ignition wires.
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From: Illinois
Originally Posted by ford390gashog
idles high = vacuum leak!
whats your vacuum reading?
whats your vacuum reading?
However, it may be important to note that a vacuum leak does not nesesarily equal high idle in a carbed engine. A properly adjusted carb should be providing the correct air/fuel mixture. A vacuum leak will upset the balance and cause rough idle, stumbling ect. Higher than normal idle on a fuel injected engine could indicate a vacuum leak because the computer is compensating for the extra air by adding more fuel.
One other thing I forgot to mention: Check your oil. If the oil smells like gas it may be diluted by unburned fuel. In fact, I would change the oil regardless. Cheap insurance!
Last edited by Neb86; Dec 19, 2005 at 05:50 AM.
Postmaster
Joined: Mar 2003
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From: Spokane WA
What plugs are you running in it?
learning how to tune the carb and playing with it wont hurt anything....
I am not a fan of electric chokes personally, I like to control when its open and when its closed....
That said, I spent a few hours playing with Rod and Jet combinations yesterday, and the carb was off the truck to do the jets the first time, It is about 13 degrees here this AM and I just got off work, it started up okay, but the choke cable wasnt changing anything.... So even the simplest setups can fail.....
I forgot to reattach it last night
learning how to tune the carb and playing with it wont hurt anything....
I am not a fan of electric chokes personally, I like to control when its open and when its closed....
That said, I spent a few hours playing with Rod and Jet combinations yesterday, and the carb was off the truck to do the jets the first time, It is about 13 degrees here this AM and I just got off work, it started up okay, but the choke cable wasnt changing anything.... So even the simplest setups can fail.....
I forgot to reattach it last night
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