Cliff's Quadrajet Parts and Rebuild Kits
General Category => Quadrajet Carb Talk and Tips => Topic started by: FStanley on April 24, 2016, 12:20:54 PM
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I have a 1979 Olds 350 Vin code "R" Federal 49 state car with 800 CFM quadrajet with:
Primary jet .073
Primary Rod .055
Secondary Rod .0530
I live in California and need to smog this car every 2 years.
I have had the carb rebuilt, all new ignition, new EGR, New cataylic converter checked all for vacuum leaks, operation, timing, all to stock specs, etc.
I seems I need to buy new Catalytic converter every 2 years to make it pass.
maximum Specs at Mph
15 Mph 139 HC 0.90 CO 913 NO
25 Mph 116 HC 0.76 CO 815 NO
Passed test measurements:
15 Mph 5 HC 0.00 CO 537 NO
25 Mph 16 HC 0.00 CO 715 NO
I think too much unburned fuel is being dumped into Catalytic converter and burning it out.
Curious, I found a 1975 year Olds 350 quad used .067 jet and .041 rod. but smallest rod end is .026 same as 1979 so less WOT fuel then in 1979 because of .073 jet.
Wondering if this is burning out catalytic converter or ??
Ideas please and thanks!
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The 1975 Olds q-jet is a completely different design, so you can't compare the jet/rod set-up to the 1979 model, it just doesn't apply. They used a front located APT system, and most had a secondary power valve and single jet/rod to add additional fuel. I avoid those carbs here if at all possible, they were only used in 1975 and early 1976 until they figured out a much better way to control part throttle A/F using tapered metering rods and an APT adjustment screw.
The 1979 carburetor uses tapered metering rods, most had "K" series rods in them, which provide very little control of part throttle A/F using the APT system. They could be "P" series rods, which would provide more adjustment as they taper .010" on the upper section vs .005" for the "K" rods.
It's also likely that the primary power piston arms are bent anyhow, and they MUST be exactly even on those units for the APT system to work correctly. Nearly 100 percent of the "rebuilt" carbs I get in here that don't work correct, woln't lean up and will not get thru emissions have bent arms for the primary metering rods.
There are other things that effect fuel delivery to the engine not related to jets and metering rods. Float height, fuel pressure, and the size of the fuel inlet seat are big players here. I'll bet the carb was "kitted" with the wrong size fuel inlet seat, and the float height may not be correct as well, which throws things off some.......Cliff
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The "passed" readings indicate you are running lean, not rich.
The high NOx readings indicate that.
I'd like to see it a little fatter. Is your EGR working? Plugged EGR ports maybe?
Too lean a condition, can also wipe out a catalytic converter, although not as fast as a rich condition.
What do the plugs look like?
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Update
More info
Carb is #17059253
Primary Jets: .073
Primary Rods: 055P
Secondary Rods CV
Power piston spring 17051705
Float: 13/32"
Had a friend check out the info above. I think stock specs for 1979 Federal(49 state) 350 Olds Delta engine
not quite sure I want to change jets/rods , car runs REALLY well all speeds. it just won't smog easily.
See original thread start for other info..
could APT, idle mixture screws, etc be off?
How to best adjust for smog?
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Update
More info
Carb is #17059253
Primary Jets: .073
Primary Rods: 055P
Secondary Rods CV
Power piston spring 17051705
Float: 13/32"
Had a friend check out the info above. I think stock specs for 1979 Federal(49 state) 350 Olds Delta engin
not quite sure I want to change jets/rods , car runs REALLY well all speeds. it just won't smog easily.
See original thread start for other info..
could APT, idle mixture screws, etc be off?
How to best adjust for smog?
Stock metering jets/rods are correct. The power piston spring isn't original though. What are your idle mixture screws adjusted out to? How many inches of vacuum are you pulling at idle?