q-jet

[jvanderveen22]

any of you guys running a q-jet have to rejet it when you installed it. since most of them come on a 350? i was trying to use my motorcraft 2bbl but i cannot find a set of 43-44 jets to save my ass. everyone at the wreckers is on a 351w/m or 400. found a set of 50's but once tuned i cannot turn the idle down enough. frustraiting deal to say the least/ its a simple fix butjust cant locate the jets. so i have a q-jet i want to use cause they work about the same but the 4 barrel would be nice for the sand. just wondering if i should hold to put it on if it needs jetting.

[Rlemon]

Re: q-jet

Hello I am running a jet stage one Quadrajet right out of the box on a offenhauser spreadbore. The only thing I did was lower the float level to help with off camber stuff. I have had it in the rubicon several times and it has run perfectly. I have had peaple ask me if I running fuel inj as they stumble and choke across the rocks as I used to do with my afb. The only problem that I had is a slight off Idle stumble and set float to low. This summer in Coos Bay had fuel starvation problems and a pump failure. I believe BC has good info in tech section.

[earlybronco72]

Re: q-jet

I run a q-jet, and didn't worry about rejetting. Just make sure you don't get the electronic one. It will run to lean. If I remember right, the small q-jet is a 725cfm carb.

[CityHick]

Re: q-jet

DEFINITELY don't get the electronic one... they are terrible to work with. My Dad's old K5 had one and it never ran right.

On the other hand, I have a plain jane Qjet from a 78 Camaro with a 350. A $15 rebuild and my engine purrs like a kitten and if you want throttle, you got it! Granted I'm running a 351w, but I believe you could tune it for a 302 without much trouble.

[Fordfreak]

Re: q-jet

DEFINITELY don't get the electronic one... they are terrible to work with.

i was a gmc mechanic for 18 years at a dealer with a smog license. i got stuck with the feedback q-jets all the time. without a computer ,02 sensor,and mixture control solenoid operational they do run very lean. i still have lots of jets/metering rods for the q-jet if you go pre83 q-jet. as long as the well plugs are sealed and the emulsion tubes are in place in the top cover they work great ran them on all my jeeps when jetted right.

[jvanderveen22]

Re: q-jet

thanks guys. i ran it on my 400 for a bit then moved over to the 2bbl. now its way to rich for the 302. i figured those little primaries would straighten that out and the bog dump on the top end would be nice. ill get a rebuild kit for it and throw it on. other than that bronco is ready to play again after killing the 400. then its on to rebuilding the doors and top.

[Sierra Backwoods]

Re: q-jet

I found a Q-Jet at the garbage dump, brought it home and rebuilt it with the $15 rebuild kit, bolted it on my 350 SBC in my CJ-5 and it has worked great ever since!

I've run Holley, Edelbrock (Carter AFB) and Ford 2bbl stockers on various 4x4's and the Q-Jet is by far the best in my experience when it comes to off-camber carb performance.

[jvanderveen22]

Re: q-jet

ok rebuilt teh qjet and now i cant get it to idle below 800-900. as soon as i get it turned back to that point it just dies. the air mixture screws arent having any effect on the idle at all. im figureing there has to be some kinda vacuum leak at the carb base some where. im only ruleing out the manifold because the 2bbl would idle nice and low on it, it's just jetted too rich. this is driving me nuts. could also be the adapter plate is warped. ill tape the carb base to see if it straightens out. what adapter did any of you guys running the q-jet use?

[earlybronco72]

Re: q-jet

It has been about eight years, but I think I got mine at Checker. I would definately look for a vacuum leak. If you cup your hand over the primaries, or close the choke down, does the idle rise? If so you definately have a vacuum leak.

[jvanderveen22]

Re: q-jet

yeah if i push the choke plate down it increases about 500 rpm. really willing to bet the adapter plate is warping.

[twister01]

Re: q-jet

I spray w-d 40 around the base while engine is running and see if the idle raises.If it does you definetly have a vacuum leak.

[Rlemon]

Re: q-jet

Check your base gaskets to make sure they are the correct size for the manifold and adaptor. I had a base gasket that had a relief on the back side between the bolt holes which left a slight gap at the manifold that I didn't see. This caused a vacume leak and same symptoms as yours. Just as a side note. Somewhere on one of the bronco club sites there is a tech artical about using the spreadbore adaptore with the primary and secondary holes as apposed to the open center adaptor. Then you flip it over and redrill the holes. This allowed the primaries and secondaries to be isolated. This causes there to be more vacume accross the primaries which the quadrajet needs and allowed for better low end response and tunning. I did this with mine and it seems to work well. Can't remember all of the thread but that is it in a nutshell maybe somone else has seen this and has more to add. I will cont to look for it.

[earlybronco72]

Re: q-jet

When I installed this last q-jet, I missed a vacuum port on the back of the carb. It was a huge leak, and I could hear it sucking. The other thing I was told is to use the thick gasket. It is about 1/4" thick. I had to go to longer bolts in my adapter.

[Rlemon]

Re: q-jet

Found one thread but I have seen a better one. http://www.emotoman.com/qjet/qjetinstall.html

Not sure who this is?.

[Fordfreak]

Re: q-jet

Check your base gaskets to make sure they are the correct size for the manifold and adaptor. I had a base gasket that had a relief on the back side between the bolt holes which left a slight gap at the manifold that I didn't see. This caused a vacume leak and same symptoms as yours.
.

i have run into this too. there are several different q-jet base gaskets and a lot of the differerences are around the vac tap boss for the power brake threaded area at the back of the carb. i got my adapters through tognottis here in sac. i think they were made by trans-dapt. if they are still in bus.