: couple of quadrajet questions

03-16-09, 09:05 PM
are there any difference between the qjet for 307 olds and a qjet for a chevy 350.

id like to use the computer controlled carb i have on my chevy 350 motor.

will the bolt patterns match?

03-16-09, 09:23 PM
The bolt patterns match, BUT, different engines, different calibrations, different idle circuits, different primary and secondary metering rods, different secondary air valve opening rate, different secondary metering rod hanger heights, maybe PCV flow rate, choke operation.

They look close to the same, but the beauty of the Q-jet series is that several internal changes can make the carb operate a 280 cube engine or a 572 cube engine.

It's all magic. Get the HP book by Doug Roe, "Rochester Carburetors", and study.

03-17-09, 09:26 PM
The Q-jet on an Olds engine has a front fuel inlet. I think it may on certain Cadillac engines too.. The Q-jet on a Chevy engine has a side inlet. It's a PITA to fit one to an Olds engine. The linkages for the throttle and kickdown cables are different.

Of course the previously mentioned calibrations.

A Qjet from a 305 would probably run well if you could get the linkages sorted out. The mixture is controlled by the computer anyway.

03-17-09, 09:34 PM
It won't work the Olds fuel inlet will hit the Chevy thermostat housing. You can buy feedback carbs for chevy 305's all the time pretty cheap.

03-17-09, 10:59 PM
My bad, I was being dyslexic. I somehow thought the OP wanted to use a chevy carb on an olds engine. Then I re-read the post and realized it was the other way around. lol

03-18-09, 12:26 PM
happens to the best of us...lol

submariner409, oddly enough i found this book with all my car manuals, not sure why i have it cause ive never read it.

so bottom line is i should just get a chevy qjet.

anyone have experience running an electric pump to these carbs?

03-18-09, 08:19 PM
You can run an electronic pump, preferably with a pressure regulator, but the mechanical pump is cheap and very reliable.

03-18-09, 10:48 PM
i totally agree. this car is my first mechanical fuel pump and i love it. unfortunately the block i am putting in the car does not have a provision for one.

03-20-09, 10:19 PM
I'm interested- what are you trying to do? How new is the 350 you want to put on?

I've successfully run the 307 CCC system on a 350 Olds, for a while. It's fairly reliable. If you're going to use the CCC Q-jet, it would not hurt to either put smaller needles or larger jets in the secondaries.

I kept getting a code for TPS even though I'd changed it twice (which btw is a royal PITA). I traced the harness all the way back to the ECM. I think the problem was a couple bad from the get-go TPS's. This system works ok because the 307 olds and 350 olds are very similar engines with similar torque curves and fuel demands... the 350 just needs more of it.

Anyway, I finally put a 'Holley 450 economaster' carb on my olds 350 with a standard vacuum advance distributor. No EGR. The only emissions controls on the engine were a catalytic converter and PCV. It runs extremely well.

This setup is soon to be in my 81 CDV... it is currently in my 84 olds 98 coupe which is pretty much the same car. With the overdrive tranny and no lockup, and a 2.93 axle, I get 21 mpg on the highway, and average 17. That's pretty good for a large car with a 350 engine.

The CCC Q-jet will not do that well mated to an incorrect engine. It'll run acceptably well under most conditions, but not as well as a standard Q-jet, or a holley, or better yet, the TBI system from a later Chevy.

If you insist on running a CCC system on a chevy 350, I'd suggest finding a 350 equipped CCC car and grabbing the whole mess including the ECM. It'll be programmed for the proper timing curve, and the Carburetor would be setup to that engine.

Bear in mind that the CCC systems while being IMO fairly reliable systems, were engineered with one thing in mind: emissions. I'm not a big fan of intentional polluting, but if you're after improved performance.. but if you're going to upgrade your engine, you probably should upgrade the fuel supply.

03-22-09, 10:42 AM
the chevy 350 is out of a 90 fwb. i have everything i need to convert my 89 fwb (307) to tbi 350. minus a standalone wiring harness for the tbi system. the more i thought about it, the more i liked the carbed system and a lot less work to just throw a carb on the 350 and retain the carb comp and harness.

but if the comp. wont run the carb as good on the 350...well thats a problem.

03-22-09, 03:14 PM
It'll probably run ok- I'd be sure to get a CCC carb from another Chevy 350 and try that. That's going to run better than the Olds carb.

It would run better yet with a complete CCC setup for a Chevy rather than an Olds.

But if you were going to go to that length, it'd make more sense just to upgrade all the way to the TBI setup- it's not that hard. It would also be good for a few MPG's

Simplest yet would be to just run a non computerized carb and distributor on the engine-- There's an endless supply of upgrade and retrofit kits for a small block chevy.

Hook up fuel, vacuum advance, adjust your timing and mixture and drive. The downside is that you'd lose your lockup torque converter unless you used one of the kits availible out there to operate it without the stock computer. (== reduced fuel economy)

There is a chevy TBI group on yahoo- I've been there before and joined as a member. There are a lot of knowlegeable guys out there. The TBI system would run well in your car if you got it setup right.

03-23-09, 10:12 AM
so many decisions....