Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

is it ok to mix and match metering rods

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lightning boy:
You can try a richer rod no problem. Bit be careful chasing afr numbers. If you see and improvement good deal. If not go back to the old ones. If it is lean at part throttle it will buck and surge. Give the motor what it wants, don't trust the afr.

MRSOFTE:
Was just out driving with no surging at cruise as far as I can tell. Nothing jumps out at me no pinging leaning into it, feels good, and I bumped up the timing 5 more degrees to 32 total all in by 2500.  That made the throttle a little crispier.

I will put in one 46 rod today just to richen the cruise a tad.

77cruiser:
I'd go up more on the timing.

Kenth:
Factory jetting for 7043213 is #74 jets and 44B primary rods. DA secondary rods and 7036019 8 - 4 in/hg power piston spring.

Burning the eyes at idle indicates a too lean idle circuit, has very little if anything to do with the power piston spring.
With todays fuels the only thing i would do in your carb is opening the idle/low speed jets (tubes) to about .039"-.040" for a proper combustible mixture.

Remember the engine is running on the idle/lowspeed circuit up to about 35-40 mph before the main circuit/jetting complements the mixture, and at that (engine) speed the factory jetting is adequat.

And, with a properly set up/modified carburetor there is seldom, if ever, a need for a modified ignition curve.

HTH

MRSOFTE:
Finally got time to respond. I mentioned the 12HG spring as the engine, IMHO makes low vacuum. My Vac gauge shows 12-12.5 Hg and who know how "accurate" it is. So I believe that maybe the spring was pushing the rods up a tiny bit. At the same time very black water was dripping out the tailpipes. It was nasty.  I made two changes at the same time. Went with Cliffs black spring and 48 rods.
This car has very low static compression at 120PSI all within 1–2 lbs. This car is a survivor unicorn.
Lived in a dry garage its whole life and stopped being driven in1978, then from 78 to 82 summers only after that to 93 only driven once to the PA inspection station for a new sticker. I thought it important you knew something about the engine. Perhaps with time and some miles the compression will come back up, and I'll get better combustion action.                                        So with 74-48 and black spring combo.
Getting cold start 1st step down 13.2ish, warmed up idle A/F 14.3-14.6ish 40mph 15.2-15.8ish 60 mph pretty much the same as 40 WOT 11.5 then it comes up to around 12. And moved the Acc pump rod to the back hole. That alone made the engine much happier right off idle. But maybe it's not getting enough pump shot at tip in? I have to drive it more and watch the AF gauge.

These changes have made it more enjoyable to drive and no more soot black condensation puddles on the garage floor or choking clouds of fumes.

Not crazy about drilling bigger passages that is too permanent for me with this car. I think I have pretty good control over the idle screws? Maybe more experimentation is required? Haha. What's a good test for that please.                                                                                                                  All I want is a nice driving experience with minimum fuss. Converting over to electric choke since I have blocked off the intake/carb heat crossover. And need the high idle to step down faster.

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