Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

Edelbrock 1910 850 tuning

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matt69olds:
As the title says, trying to dial in my Q-jet after some engine upgrades. The carb is stock with the exception of Cliffs updated accelerator pump. I tried the metering rod "tip in" procedure with the old combination, with the metering rod adjustment screw all the way down engine speed JUST started to climb. I'm guessing I need a smaller jet and/or different metering rods? My 2nd issue, the idle mixture screws have little effect on idle speed, once again with the screws almost fully seated seems to work best. Do I need different idle air bleeds or other changes? If I need to get into the carb to make changes Id like to do it once. I also installed a Innovate LM1 air/fuel gauge, best I can get is 14.2 cruising, 14.5-14.7ish at idle. WOT reads 10.9-11.00?!!!! Can that be correct?  After reading some of the tech questions it would seem most people don't care for using the LM1 for tuning, but the numbers do seem to confirm my suspicions. Opinions? Haven't been to the track yet this year, best car ran last year was 11.74. Thanks.

69 Cutlass, 3900lbs with driver
455, 10.9 compression, stock Edelbrock heads, Torker intake,  Comp Cams custom roller cam 248, 255 .050 .577/608 lift. TH400 with Gear Vendor, 3800 10 inch converter.

Shark Racer:
Changing a jet will impact cruise and WOT. Changing rods will impact cruise only (as long as you swap with the same power tips).

Where in WOT are you seeing this AFR? I test the primary jetting by pulling up hills and giving about half throttle.

Secondary rods will come into play with WOT as well.

I think you can go a little leaner on the cruise, 14.5-15 should be good.

So my recommendation would be to find a hill and verify your primary AFR (should be mid-high 12s) and then after you've got the jets locked down, re-adjust cruise. Then tune WOT with secondary rods.

Good luck!

matt69olds:
I have a bunch of metering rods and jets, I assume the all will interchange as long as they are from the same "family" ot carbs? Meaning if the are all from APT style carbs? I havent disassembled my carb yet, according to cliffs book the Edelbrock 1910 should have a 72 jet and 52m rod. Got any opinion as to what I should swap in? Hopefully I have the parts needed.

Shark Racer:
Jets are the same across all carbs. There are two "kinds" of rods for the M4M carbs; 026 tips for the dual main air bleed carbs and 036 tips for the single main air bleed carbs (like yours, these are the "M" rods).

You really need to do the "passing" test to see if you're super rich on the primary side. If so, go down a jet size or two until you get that passing AFR into the mid-high 12s.

Going down 1 jet size may get your cruise AFR perfect, but you need to know if a jet change is required or not.

Cliff Ruggles:
Those units require "M" series metering rods.  The stock metering rods are fine for that unit.

74 jets were stock in most of those, but Edelbrock was all over the map for calibrations with the 1910's. 

Most will have huge idle tubes and small idle airbleeds with .055" idle down channels.  I've seen different calibrations in them, all virgin units, so you just have to measure everything and start from scratch with them.

Most of the ones we build here will end up with 73 or 74 main jets, and 49-52M metering rods.....Cliff

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