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21
Dialing in your rebuilt Quadrajet carburetor / Re: is it ok to mix and match metering rods
« Last post by MRSOFTE on April 30, 2026, 11:14:08 PM »
No, not going to change anything but jet/rods with this carb as it is 100% original. Will leave drilling mods to any future owner. I did settle in on 73/48 combination. Which slightly changed my previously stated A/F levels a touch more rich at cruise.
Feels better by the seat of my pants.
Its definately less fussy then a few short weeks ago.
22
Diagnose a Quadrajet carburetor problem / Re: Quadrajet Throttle Body Swap - Will it work?
« Last post by DJD OLDS 4MC on April 30, 2026, 05:53:38 PM »
Thanks for your advice.

So far, I'm 2 for 2.
However, I had to drill one of them out because the slot in the screw got buggered.

I've got a third throttle body soaking, but the screw slot feels like it's buggered too.
Another candidate for drilling!

Attached, please find a copy of the successful workflow I followed that seems to be effective in removing a buggered seized APT screw.

Hope it helps someone out there.

DJD OLDS 4MC

23
Dialing in your rebuilt Quadrajet carburetor / OLDS 4MC Quadrajet 7040251 for a Big Block Olds - Advice Needed
« Last post by DJD OLDS 4MC on April 30, 2026, 05:38:55 PM »
Hi Cliff.

I placed an order last month, and received it within a week. Thanks for shipping it out so fast!

The parts received have been installed, and my son and I are just about to start road-testing.

We’re looking for suggestions for improving a 4MC 7040251 Quadrajet installed on a 463ci (10.4:1) Olds V8 engine in a 1980 Olds Cutlass Supreme that we’ve been building for the past few years.

We’re hoping you have time to look at the included attachments...

Attachment #1: - lists the specifications for the engine, induction, exhaust and driveline for the car.

Attachment #2: - shows the original factory specifications for the 7040251 before the carburetor
                          was modified following suggestions from your book. The current modified
                          specifications are also shown.

The carburetor has a 14" to 4" power piston spring installed. 

A pair of Innovate O2 sensors installed on the engine last year show that with #69 main jets and #39B primary rods, the BB Olds will cruise at 18" vacuum with about 13:1 AFR. With the power system engaged at 5" vacuum, the sensors show almost the same 13:1.

When you have time, please let us know of any changes you feel will improve the Quadrajet before we start road testing.

Thanks very much.

DJ and Jed in NIAGARA FALLS NY
24
Diagnose a Quadrajet carburetor problem / Re: marine quadrajet 17082515 on gm 4.3
« Last post by Kenth on April 30, 2026, 09:21:42 AM »
P is about the leanest hanger there is.
Most V6 marine Q-jets i have seen has an E-H secondary rods hanger (with DH secondary rods).
If you want richer use a B-H hanger with your DG rods.
25
Diagnose a Quadrajet carburetor problem / Re: marine quadrajet 17082515 on gm 4.3
« Last post by Zyen on April 30, 2026, 04:39:44 AM »
LOL.
i understand...get cross-eyed at times looking at all these things.

rebuild kit came in yesterday for 'new' carb.  i wound up stripping couple air horn screws (which were very close to gone already), so gonna clean/install/tune new carb.  may very well be 'starting over', but this core is in much better shape than what's on there now.
gonna put it back how i received it with 71/41 and DG/P.
will update soon.
26
Dialing in your rebuilt Quadrajet carburetor / Re: is it ok to mix and match metering rods
« Last post by novadude on April 29, 2026, 12:00:11 PM »
Your cruise mixtures look good to me.  Kenth has the plan for idle and off-idle.
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Diagnose a Quadrajet carburetor problem / Re: marine quadrajet 17082515 on gm 4.3
« Last post by Mudsport96 on April 29, 2026, 11:05:47 AM »
My mistake. I was lookin at the specs for CP... not DP.    :o ill be over in the corner....
28
For Sale / Wanted / Re: A few carbs for sale.
« Last post by 77cruiser on April 29, 2026, 10:16:52 AM »
I still have it PM me your address & I'll get a shipping quote.
29
Dialing in your rebuilt Quadrajet carburetor / Re: is it ok to mix and match metering rods
« Last post by MRSOFTE on April 29, 2026, 09:07:00 AM »
14–15 degrees initial I use VAC advance.

30
Diagnose a Quadrajet carburetor problem / Re: marine quadrajet 17082515 on gm 4.3
« Last post by Zyen on April 29, 2026, 04:47:32 AM »
Quote from: Mudsport96 on April 28, 2026, 06:12:06 PM
I would use the DP rods and tweak the hanger a little to lift them higher.
while i appreciate the advice, i don't see how going to a much leaner rod can fix a lean bog on the secondaries.   at 40% the DP is 0.1157" whereas the DG is 0.1075".  even bending the hangar to get the rod to 60%, the DP is still 0.100" fatter.
am i missing something?
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