quadrajet mid RPM stumble and bog

[7228Sedan]

Hi, I am pulling my hair out trying to dial in a reman Quadrajet on my 454. Marine application in a single engine cruiser. The carb is a 7044502 Quadrajet with 70 primary jets. I'm unsure of the primary rods & spring. The secondary rods are DP with an F hanger. This thing runs perfect up to 3200 RPM, like clockwork, as soon as I bump the throttle up over 3200 the motor bogs and surges. If I give it more, it will stumble and surge until 4000. Once there she runs up to WOT with no problem other than a slightly elevated temperature. New fuel pump and filters. I set the air valve spring per Mercruiser spec at 1/4 turn. my last thought is that the piston spring could be too weak allowing the rods to be held down until the vacuum drops at 4000 to allow them to fully lift out of the jets. I know the primary rods have a lot to do with how the quadrajet runs even when the secondaries begin to open... Am I in the right ball park?

[dlong70elcamino]

At 3200 rpm depending on how far the throttle is open it might not be into the secondary's yet till you push it past that.  Check to make sure the vacuum break is working and hooked up to the air door and might have to tighten that air door spring another 1/4 turn it helped mine and be sure your IGN timing isn't too slow.

[7228Sedan]

I'd say it's a little past 50%, right on the edge of secondary coming into play. I've experienced the air valve bog before, this acts differently. Its bouncing by 500-600 rpms until it gets enough throttle to hold 4000. Then it's fine up to wot. I'll try tightening up the air valve some more and see how she responds. The vacuum brake works fine, holds strong at idle.

[Cliff Ruggles]

It's difficult to provide advice with "remanufactured" units, as they deviate far from the stock specs.  The companies building them hack them up everyplace. 

To build a carburetor for a Marine application from an automotive carburetor takes intimate knowledge of the inner workings of the q-jet.  Marine engines are heavily loaded and the carbs for them are set up quite a bit differently everyplace than an automotive carburetor.

Simply driving lead plugs into the bypass air holes in the main casting and changing the jets/metering rods doesn't come up with a true Marine unit that will work correctly in all areas, even though the folks building and selling them advertise and sell them that way......Cliff