Rich at idle

[Liquidrush]

Hello,
 This is my first post. My name is Mike, I've been a carburetor guy since the early 80s and prefer a Qjet over a holley or edelbrock any day. I've been in an out of them for many years and consider myself fairly knowledgeable with them. Until now. I bought a 79 Corvette, an L82 4 speed car and someone had replaced the Q with an edelbrock which I have. It didn't run all that well and it was rich so I searched around for about 6 months and came up with the correct 17059211 carburetor. I bought a rebuild kit, a pair of idle tubes, a new float and a new choke pull off. I cleaned the carb in Napa 5 gallon bucket dip, then glass bead blasted it at low pressure, cleaned it again and then plated it with Caswell's plating kit. I did the body and airhorn in the greenish color and all of the steel like the choke plate, throttle parts, choke parts etc..in the gold cad. It looks great. I installed a new set of throttle shaft bushings on assembly, I epoxied the well plugs and installed the sealing rubber in the well also. I pulled the idle tubes, made sure the passages were clear and installed the new ones. I assembles the rest of it, put a lighter primary metering rod spring in, set the float and completed assembly. I set the choke pull off and installed it on the car. Of course I had to replace t he steel fuel line since they cut it for the other carb. So the car started right up, went to fast idle, the pull off did it's job and after a minute or so it was at slow idle. I adjusted the mixture screws  and it was idling smoothly. So the problem? The exhaust smells so rich you can't stand it. I mean eye watering, gagging rich. I don't see anything obvious, the car responds very well to the mixture screws and I have the hard idle screw backed all the way off so the blades are closed. I don't see any fuel dribbling when I look down the holes and even after driving a bit I put it back in the garage and it's gagging me almost immediately. I can turn the mixture screws in and the car responds to the point that it'll die if I go too lean. I don't know what else to look for, I'm going to replace the fuel pump for an oil leak problem and I'll check pressure when I open it up. I run premium ethanol free fuel exclusively too. Any suggestions?

[Cliff Ruggles]

Gagging smell from the exhaust is almost always too lean, not to rich.

Did you measure the idle tubes removed?  What size idle tubes did you install?

Those later model L-82 carbs don't have enough idle fuel right to start with and too lean jet/rod relationship as well. 

Where did the parts come from? 

[Liquidrush]

Pickup tubes are .035 and all of my parts came from quadrajet parts.com. It's definitely rich, there's black smoke.

[Cliff Ruggles]

You have to keep in mind that unburned fuel in the tail pipes can result from NOT putting in enough fuel for complete combustion, so you get some really stinky chit out the back but adding more idle fuel will cure it.

To know which way to go gently "tip-in" the choke flap and see how the engine responds?

Since you used some substandard and incorrect parts compared to what I would have supplied the issues could also be "fundamental". 

I would have supplied tuning parts, sized idle tubes and some recommendations to change a few things in other areas to help the carb work like it's supposed to..........

[Liquidrush]

At a slow idle, warmed up, I can tip the choke blade and it'll get rough and want to die. If I turn the mixture screws in to the point that it barely idles I can tip the blade and it'll smooth out. So what did I use that's sub standard and incorrect?

[Cliff Ruggles]

I've never found .035" idle tubes enough for the later L-82 carbs, assuming the engine is completely "stock".    Those carb use a pretty big lower IAB which doesn't help things either.  Initial timing is also a big player with stinky exhaust, not enough it will struggle to idle and too much it will run you clear out of the shop and the wife woln't ride in it because it will stink her hair up!......

[Liquidrush]

So what all do you recommend? I don't have a problem paying, as long as I get what I'm paying for.

[Cliff Ruggles]

Lots of unknowns, but at a minimum I'd go up on the idle tubes .002", different jet/rod combo, the correct PP spring, nitrophyl float if you installed a brass one, and for sure verify the float setting and fuel pressure.  Those carbs used really LOW float settings and the pumps put out pretty high fuel pressure.  One can quickly get into trouble right there using a higher float setting with a high pressure OEM mechanical fuel pump.

You will also need the correct non-windowed high flow N/S assembly and one of my accl pumps.

There is also no reason to run premium gas in one of those engines or to avoid ethanol.  Those engine don't "squeeze" anything very hard so high octane fuel is not needed and just hurts combustion efficiency even more. 

Sadly from 1974 well into the 1980's those engines were "turds" for power production.  They had really LOW compression, too much quench area, and some of the WORST flowing cylinder heads to ever sit on a 350 SBC engine.  The factory just didn't get it right trying to make the EPA happy, but eventually figured it out and started producing heads with far superior combustion chambers and excellent flow characteristics.......

[Liquidrush]

I'm the 3rd owner of this car, it went from father to son to me. I was told it had a camshaft replacement but they couldn't remember what it is. Dual exhaust with no cats and I gotta tell you, it really runs great for what it is. The camshaft is why I used a lighter power valve spring. I can't recall what I set the float at but I always set them a little low to compensate for play in the float parts. Whatever else you need to know just ask and I'll tell you what I can. Put me together what I need and let me know the cost. Feel free to email me at ezgeo1@gmail.com.

[Cliff Ruggles]

The camshaft change may be a good part of the problem.  The factory cam was wide LSA to reduce overlap.  Anything from the aftermarket would have been tighter LSA. 

Those heads also have deficient exhaust ports which doesn't help the stinky situation when teamed up with aftermarket cams.

I'm still assuming it has the factory 882 castings on it.  They may have been changed out as well, and possibly thicker head gaskets installed, etc.....