Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor
Rich at WOT, lean at idle and cruise
modrummer:
--- Quote from: 77cruiser on May 30, 2018, 09:19:37 AM ---How long does it take for the pulloff to release from fully pulled in to all the way out?
--- End quote ---
I'll test this tonight. I'm assuming I can just apply a vacuum to the hose to test this?
I'm wondering if I could fix the WOT issue with M series rods (maybe 50m). The bigger .036 tip might be what i need to lean out that mixture a bit more.
Cliff Ruggles:
It's already lean on the primary side so that will only make things worse.
The order for tuning is to get the idle system up to par first.
Then determine the best main jet size with the .026" tipped metering rods.
Then dial in the part throttle A/F with the correct primary metering rods using the APT system.
Then leave all that alone and tune the secondaries for best power at WOT throttle......Cliff
modrummer:
--- Quote from: Cliff Ruggles on May 31, 2018, 01:57:28 AM ---It's already lean on the primary side so that will only make things worse.
The order for tuning is to get the idle system up to par first.
Then determine the best main jet size with the .026" tipped metering rods.
Then dial in the part throttle A/F with the correct primary metering rods using the APT system.
Then leave all that alone and tune the secondaries for best power at WOT throttle......Cliff
--- End quote ---
I was thinking more along the lines of that I have 10:1 A/F at WOT, so a fatter power tip of the M rods would lean out that part. My cruise is sitting at 12.5:1 so I think it would be fine with the fatter rods leaning it out as well.
But I see what you are saying about getting the idle dialed in first. I was more thinking ahead that with my WOT mixture SO rich I may end up needing to try some of the fat tip rods to lean it out.
Your book should be at my house today or tomorrow so I will read up this weekend.
Plan of action is to drill out idle mix screws a small amount (.090) and see if that gives me enough adjustable range. If not, I will look into changing the idle tubes.
Thanks for the help, I'll report back when I make some progress.
Cliff Ruggles:
It will need bigger idle tubes, DCR's and probably some bypass air for the idle system.
Keep in mind that the idle system feeds the main system at light throttle thru the transfer slots so very important to start there first.
I'd also check the MAB size in that carb, it should be quite lean on the primary side with small jets in it.
Dial in the primary side first, idle, then heavy throttle, then cruise with the APT.
Forget using the primary side for WOT, do all that with the secondaries after you get the primary side up to par for what you are doing........Cliff
modrummer:
--- Quote from: Cliff Ruggles on June 04, 2018, 03:44:29 AM ---It will need bigger idle tubes, DCR's and probably some bypass air for the idle system.
Keep in mind that the idle system feeds the main system at light throttle thru the transfer slots so very important to start there first.
I'd also check the MAB size in that carb, it should be quite lean on the primary side with small jets in it.
Dial in the primary side first, idle, then heavy throttle, then cruise with the APT.
Forget using the primary side for WOT, do all that with the secondaries after you get the primary side up to par for what you are doing........Cliff
--- End quote ---
Ok so your book came in end of last week and I spent some time reading it over the weekend while I worked on the car. Nice work! Wish I would have bought it sooner! I kinda picked and chose what sections to read for now, but I'll go back and read the rest when I have more time.
I made some progress on the carb. Took it fully apart and measured what passages I could with a digital caliper and some drill bits.
I also drilled out the idle mixture screw holes to .093".
The Upper and Lower MAB passages were both about .120" according to my measurements (does that sound right?)
I lowered the APT screw another turn since I was running rich at cruise.
I also loosened the secondary vacuum doors spring a half turn and bent down my secondary hanger to .650" to lean the mixture out a little (running CH rods currently, as I understand it these rods should be pretty lean already?)
MADE A BIG DIFFERENCE! With idle mix screws 8 turns out, I have 13.5:1 at idle (is this about where I should be once warmed up, or should I make it a little leaner?)
My cruise at partial throttle is around 13-14:1, off throttle coasting or going downhill it is running rich at about 12:1. So I'm thinking I need to lower my APT screw a bit more to lean up the cruise.
WOT is better, but not perfect. Not much hesitation as it transitions to the secondaries, but it does peg 10:1 A/F for a split second right as I go WOT before settling around 11.5:1.
One thing I noticed, there is a small tear in the accelerator pump rubber seal. Any idea what kind of issues this causes? I plan to order a new one from you, but I wanted to do a few more tests this week first to see if I need anything else from you before I order so I don't have to pay shipping twice.
Thanks again for the help!
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