Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

Rebuilt Rochester E4ME on a 1981 Corvette Code 45 Running Rich on Highway

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Reaper19:
I went out and bought a vacuum gauge today to help set the carb mixture screws and IAB along with using the dwell meter. I also brought the idle down to what the under the hood label and manual recommend, it is now set to 500-550 RPM while in drive, before it was around 650-700. The timing is set at 12 degrees BTDC, factory is 6 but my other corvette club members and gear heads are recommending 10-14 for best performance, do you agree?

The vacuum is sitting right at 18 1/2 now. The high end was 19 and 18 1/2 looks to be the sweet spot with the most stabile needle. Afterwards I readjusted the IAB to further stabilize the vacuum and allow the engine to run as smooth as possible. Ran the engine at 1800 RPM for a minute or so to get it in a closed loop, watched the dwell go up to 53 and then settled in at 31.5 at idle. This was the first time I was able to achieve a dwell close to 30, stable and hunting a half point up and down. Took the car out for a test drive and what a difference when accelerating from a stop or WOT, no hesitation at all and very responsive. But I still get a CEL at 50MPH or higher cruising speed and code 45, rich condition.

Next steps will be counting the numbers of turns to bottom out the lean stop and then back it out again to the same point for reference since it had to be removed by the carb rebuilder to install a new M/C and I am not sure if he placed it back in the same spot. The rich stop appears to be set at the factory setting since the plug is still installed. I also checked the space between the M/C rich and lean stop and it is right around 3/32, the setting recommended in the shop manual. I plan on turn the lean stop in a 1/4 turn at a time and test drive to see if that corrects the rich condition.

Cliff Ruggles:
I'd go back into the carb and check float height, and see if they even put the correct N/S assembly in it, most likely not. 

Fuel level is a big player with fuel delivery, and effects the calibration more than most folks think.

I would also set up the M/C solenoid and metering rod limit screw to be fully adjustable without taking the carb apart, then you can fine tune it to get it within "range" after it is verified that everything else is correct.

I'd also recommend installing our kit while it's apart, far superior parts than what they would have used in it.  Our pump has best seal on it in this industry, it is NOT the same as the blue seals others are using, and our pump comes with custom wound springs for increased efficiency and performance........Cliff

Reaper19:
Thanks again Cliff. I am waiting for the car to come back from the engine rebuilder for its 500 mile checkup, oil change, check torque on bolts etc. Once I get it back I am going to try a few more electrical checks, float level and M/C lean adjustment height, and possibly change out the ECM if necessary. If all still points to carb and I have issues with the carb I am going to give the local carb rebuilder one more chance and if he cannot dial it in ask for a refund and purchase one of your kits. I checked out the carb number (17085204) and it is the proper model used by GM on multiple cars from 81-90.

Thanks

Randy

Cliff Ruggles:
It's probably unrelated to the rich running condition (but could be a "player"), but SBC 882 heads are complete "door stops".  They are the WORST heads to ever sit on a 350 engine that left the factory.  Very poor flowing, and super-restrictive on the exhaust side.  This was done for emissions most likely, to hold back exhaust flow to lengthen burn time and/or more time for the CAT to do it's work.  Not sure about any of that, but we NEVER use those heads for any power level or type of SBC engine build.

624's were a tad better, but every set I've ever seen was cracked as they are paper thin.  I'd put a set of World Products heads on my wish list, or even a set of factory 441, 336, 487 or 993 castings would be a HUGE upgrade from where you are at now.......Cliff

Reaper19:
Hi Cliff,

Just an update, I talked to the carb re-builder again the other day and told him I am still having the same issues. He said he would rebuild one for me that was never touched and this would be the first time it was rebuilt. He asked for the series number on the carb I had, come to find out I had 17085202 that the previous owner put on the 1981 corvette which is actually from a 85 Monte Carlo SS or Trans AM H. O. So I looked up the carb that should have come on my 81 vette and it was 17081228. So he found one that was never rebuilt before. I put it on the car and so far the rich condition is gone   :-) after taking a pretty good test drive. I installed it on the car along with a new stainless steel fuel pump-to-carb line. The only item I will need to address is readjusting the TPS to correct the lockup on my tranny after adjusting the idle. They installed all the plugs this time so I will need to drill out the TPS plug for adjustment.

Do you sell the replacement plugs only for the TPS, Lean and Rich adjustments or have a good idea what I can use to plug the TPS adjusting hole back up?

Thanks again, Randy

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