General Category > Quadrajet Carb Talk and Tips

Hesitation when taking off

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Kavesh:
Hi

I am trying to resolve a hesitation on take off on my quadrajet 7029282 which is on my Holden 308 stock standard engine. Motor has been recently rebuilt with 30 over pistons.

I rebuilt the carb in 2018 or 2019 with Cliffs rebuild kit with a new plastic pull off.

It has always had the hesitation but due to engine issues which was only now sorted I have not tried to fix the hesitation.

The internal parts on my quadrajet are 71 jets, 45B primary rods, AN secondary rods on a B hanger. (Do the hangers make a difference). Float is set at 10mm measured from the toe end of float.
Is this combination good for this engine. I am looking for good driveability and economy.
When cruising at 100-120km/h the motor is running really well.

I would love to get rid of the hesitation on take off. I really have to feather the accelerator to be able to get away from stand still.

I would appreciate any advice on this

Cliff Ruggles:
Light throttle hesitation is usually too lean right off idle.  I see this a lot building carbs here as nearly every one has the power piston hanger arms bent so the metering rods are not correctly located in the jets.

It can also be caused by the timing not advancing or not enough or too much of it.

Are you using vacuum advance?  If so how much and ported or manifold vacuum source?....

Kavesh:
I am using a vacuum advance and my source is manifold

When you say lean condition, meaning that my jets and rods on the primary side may be incorrect, as in the 71 jets and 45B rods? If so where I am located its not easy to find replacement parts and right now shipping small parts from USA is just not economical.

I can also confirm that the power piston arms are not bent and the rods are indeed in the jets.

What I have noticed is that I am not getting a good squirt from the accelerator pump. My pump is good and all openings are clear. When I disconnected the accelerator pump linkage from the primary shaft, and activate the pump with my hand, I can see really strong squirts on both sides. But with the linkage back on, the squirt is rather weak. Would this have anything to do with the hesitation I am experiencing?

Kenth:
Are you setting the idle mixture screws at idle in gear (A/T) for highest rpm/vacuum?
Can you have engine run worse with screws turned out from best setting?
If not, you may have to open idle fuel tubes and idle down channels some, ususally 2-5 thousands of an inch at both locations, start small.

Kavesh:
Hi

Yes I have set the idle mix screws with the transmission in drive.

My understanding and I may be completely wrong here is that the mix screws does not affect off idle take off, the accelerator pump and jet and rod combination comes into play.

I would not be comfortable to make changes to the idle tubes.

This carb is the original carb from factory so in theory should not require any modifications, unless i am missing something?

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