Q-Jet Primary Throttle Shaft
Thread Starter
Burning Brakes
Joined: Aug 2006
Posts: 1,058
Likes: 27
From: Eastern North Carolina
Q-Jet Primary Throttle Shaft
Hello All,
I am in the process of rebuilding my carb and noticed some slop in the primary throttle shaft. How much play is too much? The play is not interfering with the operation of the butterfly. I'm rebuilding the carb in hopes of solving a rough idle problem, the idle speed has always been consistent. Thanks for your thoughts...Tim
I am in the process of rebuilding my carb and noticed some slop in the primary throttle shaft. How much play is too much? The play is not interfering with the operation of the butterfly. I'm rebuilding the carb in hopes of solving a rough idle problem, the idle speed has always been consistent. Thanks for your thoughts...Tim
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Well, you really should have tested how much vacuum at idle you lose with the 'loose' shaft before you took it off the car. There are mechanics that say ".002 play is too much" or ".004 play is too much". But, really all that counts is whether that extra shaft play allows more than about 1" Hg loss (or more) to your idle vacuum level. The easiest way to do that is to measure vacuum level at idle; then, while still running, use some Pla-Doh or clay to seal off the outside ends of the throttle shaft and measure vacuum again. Less than 1" Hg difference?....leave it alone.
Melting Slicks
Joined: Jul 2006
Posts: 2,291
Likes: 492
From: Salmon Arm, BC
My throttle shaft was quite sloppy, so I replaced the bushings. While I had things apart I noticed some wear on the throttle shaft, and measured the difference....turned out to .004" clearance (worn shaft to new bushing). Concerned that that was too much, I talked to Cliff from http://www.cliffshighperformance.com/ and he assured me that that was OK, and went on to say that they were never that tight from the factory.....so I should be OK.
If you aren't having any idle quality issues, then I think you don't need to worry about new bushings.
If you aren't having any idle quality issues, then I think you don't need to worry about new bushings.
Thread Starter
Burning Brakes
Joined: Aug 2006
Posts: 1,058
Likes: 27
From: Eastern North Carolina
Finished with rebuilding the carb and the good news is the idle is great. The bad news id I broke the actuator off off the TPS sensors. Oh Well at least my original problem is solved.
