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81
Quadrajet Carb Talk and Tips / Re: Opinions on these "custom-50m-metering-rods"
« Last post by Kenth on January 19, 2026, 11:35:24 AM »
M4 rods w/suffix J are equivalent of early no-letter rods.
M4 rods w/suffix K are single taper and step to .026".
M4 rods w/suffix L are equivalent of 4M "B" rods.
M4 rods w/suffix M are single taper and step to .036".
M4 rods w/suffix P are single taper (steeper than K rods) and step to .026".
M4 rods w/suffix S are smooth single taper to .036".
82
Quadrajet Carb Talk and Tips / Re: Opinions on these "custom-50m-metering-rods"
« Last post by GSP7 on January 19, 2026, 09:20:43 AM »
No step, but the original rods had a "dual" taper near the tip.
83
Quadrajet Carb Talk and Tips / Re: Opinions on these "custom-50m-metering-rods"
« Last post by novadude on January 19, 2026, 05:27:32 AM »
I thought all OEM "M" rods had a smooth taper to the tip and no "step" like K rods, etc?
84
Quadrajet Carb Talk and Tips / Opinions on these "custom-50m-metering-rods"
« Last post by GSP7 on January 17, 2026, 08:42:07 PM »
'79 and later with.036 tip... My carb is 17080213

https://cliffshighperformance.com/product/custom-50m-metering-rods

Compared to the standard original 50m(etc) primary rod with .036 tip. with the dual taper/step

Im wondering, all things being equal, if these "custom" straight taper primary rods would need a larger jet to  run the same as the original dual taper with same size jet. Especially at off idle tip in.

Im wondering if I remove my Custom 50m rods and install my original dual taper 50m it would be richer off idle acceleration , all things being equal


.



85
Buy Quadrajet Parts, Quadrajet Kits, Service / 69 Pontiac GTO Qjet rebuild
« Last post by coakeGTO69 on January 16, 2026, 07:20:43 AM »
I have a carb off of a 69 GTO that I am going to rebuild. I am just trying to get the motor started and was thinking the standard rebuild would be best. Any advice/documentation/procedure you could provide? Someone mentioned making sure the parts do not stay in cleaner very long, any insight into the reason? Thanks
86
Quadrajet Carb Talk and Tips / Re: Contemplating Pontiac 7042262 Rebuild
« Last post by SoonerD on January 13, 2026, 10:43:19 AM »
Reviving my old thread.......I'm just now getting to actually starting to rebuild the 7042262 after having disassembled it at the time this thread was started.  I will need the choke bracket as discussed above but not sure what I need to do to get it seeing as the part is not listed anywhere on the site.

I just placed order #15958 two days ago and it would be nice to get the bracket included in the shipment, and I can pay for it however is needed.  Please let me know what I need to do.
87
Diagnose a Quadrajet carburetor problem / Re: 90% of 'Carburetor Problems' are 'Ignition Problems'
« Last post by Kenth on January 13, 2026, 09:10:25 AM »
To start with i would fix the mashed slot on air valve shaft and remove the secondary shaft lock out lever.

Then i would use #75-#76 main jets and CV, AU or CK secondary rods for better throttle respons.

HTH
88
Diagnose a Quadrajet carburetor problem / Re: 90% of 'Carburetor Problems' are 'Ignition Problems'
« Last post by Buick73 on January 13, 2026, 06:31:45 AM »
Quote from: Kenth on January 13, 2026, 04:15:41 AM
An engine must be in good mechanical condition (cylinder pressure) and have a well-functioning ignition system for the carburetor to do its job as intended.
A point breakerless ignition system where the ignition coil has too low an operating voltage will produce too weak a spark at the spark plugs and the engine will hesitate when the throttle is applied.
So, do you have good cylinder pressure and korrekt voltage to the ignition coil for the ignition system used?

Engine was completely rebuilt in 2018.  30-overbore (would have made 20, but pistons not available at that time).  Stock cam.  All cyllinders with about 180 psi.  Coil voltage at 12V to distributor (no resistor).

Yesterday, I replaced all the ignition components- new 0.040-gap plugs (see picture of old ones), wires, distributor cap, rotor, & a new magnet wheel (one had fallen out).

While into the distributor, I noticed springs were worn/ stretched; weights were floating outward & not returning to fully retarded positions.  I have a pack of various springs for it.

I put the stiffest ones in just to set initial timing (10 degrees BTDC).  Then, I started experimenting with softer ones (mix & match).  When I found the ones that I like for driving, I checked my results with timing light.  I have 26 mechanical (so 36 total), all in at 3,000 RPM.

I also swapped out my vac advance (B9) for a B27 (5-7 inHg tip-in), 18 total.  This is closer to the original spec sheet (please see attachment) than the recommended 'B1' (8-11 inHg tip-in), 16 total.

Carb rebalanced.  I found best vacuum at 2 3/4 turns from seated.  I returned both to 2 1/2 turns for best lean idle.

OVERALL RESULTS:

1. Part-throttle hill climbing has resolved.  I can climb a hill easily without having to floor it.

2. Off-idle hesitation has improved, but is still there.  Before, I was limited to about 25% throttle from a standstill.  Now, I can push about 50%.  Car accelerates smoothly & quickly 'gears-up'.  I can feel mechanical coming in.  Vacuum is probably contributing too after a few seconds as vacuum level rebounds with speed.

CURRENT QUESTIONS:

1. How do I improve the off-idle response?  If I floor it from a standstill, car dogs forward for about 2-3 seconds, then winds up & starts moving (kind of like if I had just started with 50% throttle, except now I'm 2 to 3 seconds behind).  Please see 'Results #2' above.

2. I've considered:
(a): Swapping more initial in exchange for limiting mechanical to maintain overall total.
(b): Installing softer distributor springs to bring advance in even quicker.

I currently don't have any knocking under any driving conditions, but I know I would have to be close with 36 total & another 18 vacuum.  However, I never cruise at 3,000 RPM (that would be more than 90 mph for me). So, I would never see the technical 54 degrees.

Any other carburetor tuning I'm missing?

Thanks again.
89
Diagnose a Quadrajet carburetor problem / Re: 90% of 'Carburetor Problems' are 'Ignition Problems'
« Last post by Kenth on January 13, 2026, 04:19:21 AM »
Quote from: mcx on January 10, 2026, 05:13:26 PM
…check the replaced air lid and verify it wasn’t replaced with the Buick 750cfm version, as those have the upper idle air bleeds in the air lid….the 800cfm version(7042240) do not have them in the air lid (unless custom modified)….Good luck.

Only 1967 Buick Quadrajets has the upper idle air bleeds in the air lid.
90
Diagnose a Quadrajet carburetor problem / Re: 90% of 'Carburetor Problems' are 'Ignition Problems'
« Last post by Kenth on January 13, 2026, 04:15:41 AM »
Quote from: Buick73 on January 10, 2026, 12:10:31 PM
So, I understand that people are divided on rather the Pertronix is a 'good thing' or a 'bad thing'.  But my original question was about the hesitation issue (please see original posts).

An engine must be in good mechanical condition (cylinder pressure) and have a well-functioning ignition system for the carburetor to do its job as intended.
A point breakerless ignition system where the ignition coil has too low an operating voltage will produce too weak a spark at the spark plugs and the engine will hesitate when the throttle is applied.
So, do you have good cylinder pressure and korrekt voltage to the ignition coil for the ignition system used?
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