Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Marine 454 no throttle response between 3,000- 4,000

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Cliff Ruggles:
I see this often enough that I refuse to work on anything commercial built/remanufactured these days....lessons in humility!.......Cliff

7228Sedan:
I made the changes above and took the boat out with a helper. I had someone view the secondaries as I was putting on power. I was able to dial them in pretty nice. Still getting an occasional pop through the carb from 3800 RPM up to 4000. Assuming I need to look into the hanger or secondary rods? Once I gave it full throttle she pulled hard up to 4400 RPM, perfect for the prop I'm running.

All pretty good however when I put the flame arrestor back on the bog returned. I am assuming that the flame arrestor isn't flowing enough air?

When testing a carb without an air cleaner on a car, only to find a bog after putting the air cleaner back on, what could be the issue there?

By setting up the Air valve spring with the flame arrestor off, did I not calibrate it correctly?

Thanks all!

Sonny:

--- Quote from: 7228Sedan on September 15, 2018, 11:30:33 AM ---When testing a carb without an air cleaner on a car, only to find a bog after putting the air cleaner back on, what could be the issue there?

--- End quote ---

Would that not shift the calibration LEANER?

7228Sedan:

--- Quote from: Sonny on September 15, 2018, 03:17:46 PM ---Would that not shift the calibration LEANER?

--- End quote ---

That is the most obvious...  I have a tendency to glance over the most obvious from time to time. My concerns were related to the difference in the airflow in form, not necessarily the impact the added airflow has to the mixture.

So if leaning the mixture out by removing the flame arrestor helped (possibly a bit too lean based on the popping I was experiencing) I should assume that the mixture is too rich with the arrestor on... fair enough

I will be trying a larger flame arrestor which should lean things out some. Before I make any other changes, I'll test that.

7228Sedan:
Able to put this one to bed... the larger flame arrestor solved the problem.

Thank you all for the input.

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