Quadrajet Adjustment

[specop1]

I didn't know I wasn't supposed to touch the power piston stop screw. I rebuilt my carb, and removed this screw. I didn't record where it was at. Now I have slight black smoke at idle, it runs good, but when I come to a complete stop it acts like it wants to die, but doesn't . But I do have rough idle, black smoke , and strong burn your eyes odor. Hiow do I get this screw adjusted back where it needs to be. I have it all the way down , and I'm pretty sure it was all the way down or very close when I took it out, but I guess not, because now I have this problem. Any step by step ideas to get me back to normal operation? Where are most of them set ?

[ChillrMn1]

it's possible your power piston might be stuck in the up position thereby keeping your primary rods up and out of the jets resulting in a rich condition. during normal idle, the manifold vacuum should keep the piston down with rods in the primary jets. as you increase rpm, less vacuum occurs and allows the power piston to lift starting the power mode. with engine off, try fitting something into your vent to assure you can depress the piston down and feel the spring pressure lift it back or return. refer to my previous post on this thread where i mentioned mine hung up after reassembly. of course, this is all assuming it's not just your idle mixture screws too rich. as for adjustment of the power piston screw, i don't know. this adjustment is not in my copy of doug roe's book. good luck. let us know how you make out

[woodboat]

I got my boat running today. I installed edelbrock secondary rods and hanger that closely match the good running port engine as well as the leanest power spring available. Idle is very good and smooth @ 580 RPM. Power is good. I picked up 250 RPM on the top end. I suspect fuel economy is up as well as everything is leaner.

[ChillrMn1]

Glad you're running better. I should have tried a leaner spring myself when I rebuilt mine. Next time if I have to rebuild her again. I'm sure the fuel economy is improved, let's us know what you gain.

Thanx

[woodboat]

Problem is I don't really have a baseline for fuel economy. It was flat in the middle when revved in neutral. It had a miss around 3300 RPM. It was missing a few hundred on the top end and all the plugs were black after only a few hours usage. Right now they are both running about the same which quite frankly seems very good. For small blocks pushing a 50 Footer I am actually impresed.

[SCSeaside]

I am rebuilding a QJet 17082403 that I removed from my port Crusader 454 350 HP Engine. I suspect that the float was sticking and allowing gas to flow past the cylinders and into the oil pan. Oil was very thin, watery in fact, and had a heavy gas smell. I took out 21 qts and the pan normally holds 7 with a filter change. Any pointers on rebuilding are greatly appreciated. I noted the power piston advice above. Very helpful.

[SCSeaside]

PS...I'm assuming that WOT in this string refers to Wide Open Throttle.

[ChillrMn1]

SC -
That's alot of extra fuel/oil you removed. May I also suggest the following if it's not carb problem: If you have a mechanical fuel pump, there is the possibility the diaphram in the pump is leaking. At the bottom of the pump is a fitting which should have a fuel line attached returning to the carb air horn. This is provided in case the diaphram fails so the fuel will not leak into your bilge but be "dumped" in the carb. If it is the fuel pump, then that will need to be replaced. And yes..WOT is Wide Open Throttle.

Let us know how you make out.
Bob

[maresca]

I am the first owner of a 1988 350 King Cobra 260 hp with 500 hours on it. The engine was stored for several years before first use. Since its first start I never was able to get the engine to the operating range 4200-4600 rpm. I have installed a 15X16 pitch propeller getting 4000 RPM and a 15X17 pitch getting 3800 RPM and maybe 2 miles more speed. The engine is working fine but the iddle is very unstable specially when cold and I have almost closed the idle needles to reduce raw unburned fuel but it seems these adjustement wont correct the real situation. Because of the iddling condition I took the carburator to a shop and they installed a new kit (probably automotive), but there was no change or improvement. After reading the diferent comments on this forum Im starting to think that my carbuator needs fine adjustement probably I have the wrong power valve spring, metering rods and jets or a combination. Will this items be part of a carburator repair kit or have do they have to be purchased separatelly.
Thanks for the advice!