Quadrajet too rich!

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DemarioM

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Good evening. I have an 85 c10 with a 305 in it. It's my dream since I was a child. The carburetor I've got is I quadrajet 17085226. I'm inquiring because I'm having a hard time passing emissions due to it's running too rich and, I don't know what else I can do to correct it. I'm pretty sure at this point I just need to change the jets due to the altitude. I live in Aurora Colorado and the altitude is 5,403 ft. I need help purchasing the correct jets. I'd really like be able to drive my dream truck legit but I can't get a registration until I pass emissions.
PLEASE HELP!
 

C10MixMaster

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Good evening. I have an 85 c10 with a 305 in it. It's my dream since I was a child. The carburetor I've got is I quadrajet 17085226. I'm inquiring because I'm having a hard time passing emissions due to it's running too rich and, I don't know what else I can do to correct it. I'm pretty sure at this point I just need to change the jets due to the altitude. I live in Aurora Colorado and the altitude is 5,403 ft. I need help purchasing the correct jets. I'd really like be able to drive my dream truck legit but I can't get a registration until I pass emissions.
PLEASE HELP!

to rich at idle cruise or acceleration? do you have a copy of your emissions test it would help
 

DemarioM

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I have about 7 copies, the best I've done so far is..
HC 4.7O
LIMIT : 4.5
CO 90.03
LIMIT : 45.00
 

C10MixMaster

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I have about 7 copies, the best I've done so far is..
HC 4.7O
LIMIT : 4.5
CO 90.03
LIMIT : 45.00


are these idle readings or do they do a dyno run and take reading?
 

DemarioM

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These are on a dyno
 

C10MixMaster

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These are on a dyno


OK things that's can cause hi CO and HC under load

problems with the ignition system causing a miss under load. plugs use only stock type plugs nothing fancy, no platinum's , no iridium's , no multi tipped plugs they are just going to cause you problems. check you plug wires , I like to use a spray bottle and mist the plug wire if there is a bad spot in the wire you will get an audible tick and drop a cylinder. Also make sure your mechanical advance is working.

If your ignition system is good and it is a carb problem . things to look at are float level to high will go rich, primary rods bent, power piston stuck, mains jets too big. If it is a carb issue I would build it by the book first before changing jets or any think else.

the books are here https://www.gmsquarebody.com/threads/1973-1991-service-manuals.14499/
 
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bob seifert

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Your carb 17085226 has a solinoid in it to cause a double pump in the idle circuit when cold. If its stuck open that maybe the problem.
 

peats

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emissions on a 30 something year truck??? WTF?? move to a friendlier state.
 

Ricko1966

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Couple of things come to mind, check for vacuum/ intake leaks. Make sure all your vacuum hoses are routed correctly that truck should have like 0 advance at idle from an emissions stand point so a failed tvs, improperly routed vacuum line etc. can cause you to fail.Pull some timing out and fill up with 10 percent ethanol fuel just for the emissions test.
 

SirRobyn0

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OK things that's can cause hi CO and HC under load

problems with the ignition system causing a miss under load. plugs use only stock type plugs nothing fancy, no platinum's , no iridium's , no multi tipped plugs they are just going to cause you problems. check you plug wires , I like to use a spray bottle and mist the plug wire if there is a bad spot in the wire you will get an audible tick and drop a cylinder. Also make sure your mechanical advance is working.

If your ignition system is good and it is a carb problem . things to look at are float level to high will go rich, primary rods bent, power piston stuck, mains jets too big. If it is a carb issue I would build it by the book first before changing jets or any think else.

the books are here https://www.gmsquarebody.com/threads/1973-1991-service-manuals.14499/

Your carb 17085226 has a solinoid in it to cause a double pump in the idle circuit when cold. If its stuck open that maybe the problem.
The above is great advice. Ricko, talks about timing, yes it would be a great idea to set it with a timing light, I'd only retard the timing for the purposes of getting it though emissions if everything else checks out first, but that is me.
 

squarelyfe

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It's a 750 cfm carb on a 305... It's a little rich to begin with. Get yourself a Holley 600 cfm or Edelbrock if you can pass smog with one of those. Lean the af mixtures in and check timing.
 

Blue Ox

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Check for leaking well plugs. Simple fix, but can lead to uncontrolled extra fuel in the system.
 

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