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Old 05-15-2018, 04:52 PM   #1
C-ries
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Q-Jet to Holley carb swap

Hi everyone,
I have a 1971 GMC C15 with the stock 350 engine and TH350 transmission. I am working on swapping from the stock Q-jet carburetor to a Holley 4150. The problem I'm stumped with is getting the throttle cable hooked up properly. When I hook up the cable to the bracket on the new carb the foot pedal will only open the throttle to about half throttle when the pedal is on the floor. Anyone tackle a swap like this or know of any sites/pictures of it being done?

Craig
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Old 05-15-2018, 05:04 PM   #2
geezer#99
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Re: Q-Jet to Holley carb swap

One like this might help.
https://www.google.com/search?tbm=is...yW10VwsvJhXQM:

Or simply move the attachment point for your cable up higher on the lever.
A bracket like this helps do that.
https://www.google.com/search?tbm=is...dUpkRMY9LGm7M:
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Old 05-17-2018, 08:30 AM   #3
C-ries
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Re: Q-Jet to Holley carb swap

So I looked this over a little closer last night. I had the Holley throttle cable bracket kit part number 20-88 but was having a mental block that the round peg (rubber grommet) needed to fit into a square hole. The bracket kit (Holley 20-88) does correctly locate the throttle cable to get full throttle articulation. I will post some pictures to go with this.

To get the round rubber grommet to fit into the slot of the Holley bracket I had to file the opening of the slot wider. After filing I had to pull the rubber grommet away from the plastic "stopper" on the throttle cable. Pulling the rubber grommet away from the stopper puts the grommet on a smaller diameter of the throttle cable which allowed me to squish it. Before pushing the grommet into the bracket I sprayed the grommet with some WD-40 in order to allow it to slide better. I bolted the bracket to the rear driver's side carb mounting stud and wiggled/squished the grommet thru the slot into place on the bracket. Then I pushed the plastic stopper back tight to the grommet. For the free end of the throttle cable, I reused the post off of the old carb.
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Old 05-17-2018, 07:59 PM   #4
BCOWANWHEELS
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Re: Q-Jet to Holley carb swap

Hope you like gas........... Q-jets are alot better mpg wise
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Old 05-18-2018, 10:18 PM   #5
C-ries
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Re: Q-Jet to Holley carb swap

This is my fun, sunny summer day truck, not a daily driver. In the almost 20 years of owning this truck iíve never checked the mileage! I add about 250 miles a year so Iím not worried about it.
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Old 05-19-2018, 03:54 PM   #6
BCOWANWHEELS
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Re: Q-Jet to Holley carb swap

sure looks nice
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Old 05-19-2018, 04:20 PM   #7
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Re: Q-Jet to Holley carb swap

Seems backwards. You'd think if you're mounted too close to the pivot point that the pedal wouldn't have enough travel and the throttle would be too senstive.

In fact, I just made an extension to make a throttle less sensitive by extending it even further!

If you were mounted in the big top hole I could see if. But where you've got it mounted should work. Are you sure the pedal goes all the way to the floor or does it stop on something before that?

It's not, for example, binding up on the plastic sleeve tube on the linkage cable?
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