Thinpockets

About 3 weeks ago I tied off the Quadrajet secondaries to work of the primaries without them interfering. I forget about it until today when I took it for a nice long ride.
Is there a downside to not running the secondaries? The car sure runs good.

lars

If you're only driving on the primaries, there is no difference - the secondaries only open going into WOT. But if you can't tell the difference in performance with or without the secondaries locked out, you have a throttle travel problem that is preventing secondary operation: Have someone press the pedal to the floor while you observe throttle arm movement. With the pedal to the floor, see if the throttle can then be moved further open by hand to open the secondaries. Most C3 Vettes never get the secondaries fully open due to travel problems. You can fix this by:
1. Install the trottle cable in the lowest hole in the throttle arm.
2. Grab the gas pedal and bend it upwards to provide more travel.
3. Remove your floor mat.

Thinpockets

Actually what I was looking for is some info on whether there is any idle circuit in the secondaries and are the secondary throttle plates set slightly open as on a Holley.
If there is no fuel being used by the secondaries when the linkage is disabled then I may leave it that way. I have a tendency to drive with my foot too far on the gas and I'm getting only 12 or 13 mpg - maybe this will help.

BigBlockk

There is no idle circuit in the secondaries.

BigBlockk

Later.....

mrvette

12-13 is fairly typical for an old shark on a Qjet....15-16 is more desirable,but difficult to attain....

I suggest going to a DPFI unit for economy and performance, but i'ts a techy effort, and some money spent...the aftermarket units are WAY more expensive than say an old TPI unit....long time to make up for 2-3 grand worth of update gear....but 5-700 is more doo able....

lars

There is no idle circuit on the secondary side, and the secondary throttles are not cracked open at all like a Holley - there is no airflow at all on the secondary side at idle or cruise.

There is no way you can drive the car at cruise using the secondaries. The secondaries start opening at about 3/4 throttle travel, which basically means you'd have to have the pedal to the floor before you're into the secondaries on a Q-Jet.