Quadrajet issues

[rfoll]

Just an update here. The problem turned out to be a poor quality intake manifold. In order to save about $100 I bought a Speedmaster intake. Most of the manifolds I would have ordinarily used were not in stock. When I pulled the spark plugs, 2 of them were stark white and the rest were dark and nearly fowled. Either a design issue or the manifold just plain leaked.The distributor hole was so far off center it wouldn't hold a gasket. I finally found an Edelbrock RPM in stock from Jegs and the engine runs good.

[chevyfreak]

Just an update here. The problem turned out to be a poor quality intake manifold. In order to save about $100 I bought a Speedmaster intake. Most of the manifolds I would have ordinarily used were not in stock. When I pulled the spark plugs, 2 of them were stark white and the rest were dark and nearly fowled. Either a design issue or the manifold just plain leaked.The distributor hole was so far off center it wouldn't hold a gasket. I finally found an Edelbrock RPM in stock from Jegs and the engine runs good.

Thanks for the feedback.

I was actually looking at one of those intakes to replace my cast iron intake on my 327.

Chevyfreak.

[streetperf]

I have a nice 350 on the test stand. Flat top pistons with Vortec heads. The cam is a Bullet 268. 218/268 intake, 222/272 exhaust, 110 lsa. Dual plane intake with headers and no mufflers. The original carb is of unknown origin, idled ok but a little fast. It sounded a little ragged off idle and smoothed out when revved up. It seemed to run fine when on a different engine, but was set aside for a better QJ currently in the car. I really had no intention of using that carb in the car. I have an 850 DP I just assembled and wanted to make sure it was going to work ok before I put it on the 415 in the race car. It started instantly and ran butter smooth throughout the range I ran the motor up to. Idles beautifully. Wanting a better QJ for when the test stand motor goes in a different car, I installed a carb I had rebuilt previously. The original application was 1988 motor home 454. It idles ok, but a little fast. When revved up it runs ragged all the way up until the main circuit comes into play. I'm starting to wonder if I am expecting too much from a stock QJ on an engine with a somewhat healthy cam. I like to run the QJ on my street vehicles for the good fuel economy they produce, but these to carbs aren't going to work in the condition they are now.

If the idle mixture screws do not change anything at idle the carb needs disassembly and cleaning. Submerged cleaning not carb spray. You may also have to enlarge the idle mixture orifices no more than .093". On ebay there is a place called Cliffs Performance he sells parts for QJets and offers some building tips. You can also send him your carb and he'll rework it for you. Just my @.02.

[Geoff2]

Ineffective idle mixture screws do not automatically mean the carb has to be cleaned. If a long duration cam is used, t/blades might be open so far that the carb is idling off the transfer slots, not the mixture screws which would be largely ineffectual. Fix here is to provide bypass air so blades can be closed.

[travis]

Just an update here. The problem turned out to be a poor quality intake manifold. In order to save about $100 I bought a Speedmaster intake. Most of the manifolds I would have ordinarily used were not in stock. When I pulled the spark plugs, 2 of them were stark white and the rest were dark and nearly fowled. Either a design issue or the manifold just plain leaked.The distributor hole was so far off center it wouldn't hold a gasket. I finally found an Edelbrock RPM in stock from Jegs and the engine runs good.

Welp, that answered THAT question for me. I was looking at a speed master low rise dual plane as they are in stock, and the only aftermarket idle-5500 351w is the edelbrock 2181, and the availability date just keeps getting moved out like everything else.