To make a long story short...I have inherited a 1983 Z28 (71k original miles) with a rebuilt 305 engine and "new" carb. I think that during the engine rebuild (at the dealership) they adjusted the quadrajet with vacume leaks. I have fixed all the vacume and exhaust leaks and seems like my performance has just been downgraded. Played with the timing a little but not what I wanted. The icing on the cake is that it idles rough. I know where the adjustments are on the adapter plate and are visible. If I adjust these, I just need a starting point. Anyone know of a guru of q-jet?

Geeves

 

First off is it a computer controlled model or not?

If its not start with 3 turns out for the idle screws your talking about, set the timing at 10-12 degrees and set the idle how you want, 750-800. That should give you a good start.

One problem I have is my vacuum distributor only gives about 12-14 degrees mechanical advance, so I need to set my initial timing to around 22 or my power really drops off.

Check your timing at 3000 rpms, if your not getting at least 30 degrees advance thats going to seriously kill performance.

 

Forgive me for being stupid. Don't know if computer controlled or not. I have a throttle position sensor on the front but have no idea what the two conductor top sensor is. I can unplug both wires from the carb and car will still run and accelerate. So I am guessing that q-jet is not computerized. If I can "only" get a certain advance from vacume, what are my options for replacing vacume advance.

 

If you have more than the one plug on the passenger side (choke), then it's computer controlled... basically...
yea, it'll run if you unplug those, but run like crap. ie, bad mileage, rough idle...

plug them both in. oh yea, the top 2 prong is the mixture control solonoid. if either are broken or not working that may cause your problems.

Vacuum advance: there is basically one main choice: Crane Adjustable vacuum advance. $30, and you can set your mechanical advance and vacuum advance to whatever you want, very customizable, very very very much worth the $.

Personally I don't like computer controlled carbs, hard to get parts for, not well known about in aftermarket circles, prone to problems etc...

If I were you (this is what I did a few months ago), go get a non-CC Q-jet, and a non-CC distributor (they must match, so no one CC and the other non-CC)

-J

 

oh yea, about the timing, read the HEI timing guide on TGO's main page, it's all about how to setup the Crane kit etc... Very helpful

 

Your model is computer controlled. As i dont have one i cant help you, but if you search there are many articles about setting it up properly.

 

Just wanted to say thanks and any advice given is well appreciated!

Thanks
Geeves

PS And now I have a starting point...

 

If you want advise on setting up a CCCarb check out my post in General Engine "Resurection Frustration" at the bottom there is some great info on setting it up properly.

 

Once you become familar with engine management and Q-jet the CCC Q-jet is a very simple device. I prefer to use them on vehicles they came factory equiped on due to better fuel economy and driveability. Worked on a monte carlo ss with this system and a transplanted 396 big block a while back for my girl friend. I would get the engine into a good shape of tune (plugs, wires, cap, rotor, O2 sensor, check for other dead sensors, etc), then work on the carb. It is possible that during the tuneup the problems will rectify themselves. Once rejetted with the proper jets on the primary side along with the original 396 hanger and secondary rods the CCC Q-jet stomped butt running a 12.9 @ 117 in the 1/4, idles and drives like the stock 305, averages 17 mpg, and runs like a beast when the pedal is matted. Not your average 19 year old girls car!

 

The article on "Resurrection Frustration" was perfect. Just what I was looking for. Although there is more information that my brain can handle at one time, this should keep me busy for quite some time. Just reading through it was a challenge. I think anyone who has a CC Q jet ought to atleast print that article out.

Thanks
Geeves