Ok guys when you built your Q-Jet did you put smaller jets in it? If so where did you get them, and what size are they? I ask because mine runs real rich, but it needs replaced anyway(it's got that crack problem), and I've got a good(looking) one, but I don't want it to run rich when I get the new one on.

 

I had a q-jet on my 86 and it ran really rich and could never get it to run right. I ended up taking it off and putting an edelbrock on. It was a factory reman I only ran it about 3 weeks. But if u look on summit racing or places like that u can did the jets and rods. Local parts stores can get them but double the price. If u know anyone interested in a good qjet I've got that one still just setting in the garage. I'd sell it for 75 plus shipping. Good luck hope u can get it dialed in.

 

I think so many people say the Q-Jet is such a wonder carb that we don't even think we have to tune it top get it running right. I know now that mine runs rich and the secondaries open to early, on top of the problem with the crack in the base plate. I would sure like to hear from people that made it work for them.

 

I had the same problem with my secondaries opening to early. There is a screw that you can adjust them with on the connecting rod.

Heres some info I got on how to tune and tighten those secondaries

https://www.ford-trucks.com/forums/9...questions.html

Hope some of it helps!

 

There are many things that can cause a carburetor to run rich besides jetting. You should always check things out thoroughly before resorting to jet changes.

To begin with on a Quadra Junk, you need to check the plug in the bottom. If it is leaking you can epoxy in a plug to seal it. That is a problem specific to this carb design. The basic problems that can cause richness on any carb design are power system problems, float setting, leaky needle and seat and other basics.

Although lots of people call the Quadra Jet names such as the one above, it is a good carburetor if properly rebuilt. That said, it is not a good choice for a 300. The small primary/large secondary configuration has no advantage whatsoever, due to the single plane nature of the log manifold.

 

I had an Offy dual plane manifold put on my 300. I think the Q-Jet is probably the best everyday carb you can run on a truck, otherwise people wouldn't call it hillbilly EFI. That is why I chose the Q-Jet, and they used it on small engines like the 4.1, and 4.3 Buick and Chevy V6, and probably small V8 engines in the low 4.0 size ranges.

 

BTW thanks for the link CoolGuy.

 

Like anything else, the QJet has to be tuned for the application...even an Edelbrock might stand a little tuning. Be sure it is a rich condition before you start changing things. Many mistake an off idle stumble or other tip in stumbles as a rich condition when it is actually a lean hole that is being uncovered. The secondaries are adjustable to delay their opening which is a usually required adjustment when used on these engines.

 

I can smell the fuel loading up real bad at idle, and when putting around in 1st gear. I have a whole other carb that hopefully is in better shape(loos much better). I was just wondering if people who run Q-Jets re jetted because most Q-Jets probably came from a bigger engine than 300 cubic inches. I am just wondering what guys who got them tuned good changed jets or anything else I may want to think about.

 

Loading up at idle might indicate maladjusted float level, not jet sizing.

 

If it's that bad, I would NOT be changing jet sizes, I would call that a flooding condition. Make sure there's no trash in the needle and seat, check fuel level, make sure float is floating, check power system. In such a case, an overhaul might be warranted.

In the days of carburetors when I found a carb that could not be diagnosed readily I just got a kit, boiled everything out and put it back together. That would fix the problem 95% of the time and you had a nice, fresh carburetor in the bargain.

 

You don't change the jets on the Q-jet, they are not replaceable. You change the metering rods.

 

Excess wear in the throttle shaft/bushing might cause this too.

 

The jets ARE replaceable on a Qjet as are the primary and secondary metering rods. I run a Qjet on my 3.7l 4cyl engine in my boat. It runs perfectly and the secondaries cut in just when they should and the sound when they open is awesome. Having said that the qjet was made is so many variety's and so many primary and secondary metering rod sizes that it requires one to sit down and do some serious research. You can't just grab the first one you see and bolt it on to some non-stock setup and have it work very well--that is unless you get very lucky. A good place to find bare bones qjets are marine engines. They are basic carbs with out all the fancy air bleeds and vacuum passages of car engines.
If you are serious about using a Quadrajet, get the soft cover book---How to Rebuild and Modify Rochester Quadrajet Carburetors by Cliff Ruggles. It tells you everything you need to know. I used it as my primary reference for the rebuilding of the carb that is currently on my boat after a disastrous mix master carb I bought from a large re builder failed to work correctly.

 

3.7 4cyl I bet that thing has got some torque. The only really complicated q-jet I found was a computer controled model, and of course it was useless to me. I don't know where the one I'm running came from, but the new nice one came from a 72 Blazer, and is a reman as well.