Not getting full throttle
Thread Starter
Drifting
Joined: Nov 2016
Posts: 1,957
Likes: 576
From: Pittsburgh PA
Not getting full throttle
So had my car out for the first time yesterday and got on it a bit. Noticed it didn’t seem to have enough go. Tonight I started checking and it looks like I’m not getting WOT with the pedal.
Linkage at carb works fine fine but stepping on the pedal and watching and I can see it’s not moving enough.
So is there a quick fix? Can the cable stretch that much? Searched a little. It doesn’t seem like there is any adjustment?
Didnt have ave a chance to look much further but hoping to tomorrow night
Linkage at carb works fine fine but stepping on the pedal and watching and I can see it’s not moving enough.
So is there a quick fix? Can the cable stretch that much? Searched a little. It doesn’t seem like there is any adjustment?
Didnt have ave a chance to look much further but hoping to tomorrow night
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Cable or linkage? Some guys put a bend in them or fab one up with stuff from Summit, Speedway motors etc.
Do you have someone who can floor it while you check to see how much travel is left @ the carb?:
Do you have someone who can floor it while you check to see how much travel is left @ the carb?:
Melting Slicks
Joined: Oct 2010
Posts: 2,276
Likes: 337
From: "ɹǝpunuʍop", Adelaide, South Australia
is there a floor mat under the pedal? that can stop the travel.
over the years the pedal rod can be bent / bend from too much heavy foot action.
had to re-bend my 72's rod to get full travel on mine.
over the years the pedal rod can be bent / bend from too much heavy foot action.
had to re-bend my 72's rod to get full travel on mine.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
Most problems like this are due to some issue with the accelerator pedal mechanism. Some get bent from years of use; some have problems where the cable connects to the pedal mechanism; some are just 'worn out'. But, ALL can be adjusted or repaired with a little ingenuity. Investigate the details of pedal and cable from foot to the carb. If you can't get full throttle travel with normal adjustment method (at cable connection to carb), and the cable is the correct piece for your car, the problem is in the pedal area.
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Is my vette stock?? HAHA
Joined: Oct 2015
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From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
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I did the zip tie trick to find out how much travel I was getting , the I pulled my throttle pedal and bent the arm to get more travel. I get full throw now. You should look and see which hike you are in on the linkage as well. Closer to the shaft is more pull for less pedal movement. further out needs more pedal movement. And as mentioned, make sure your floor mat isnt up under the pedal too
Last edited by Rescue Rogers; Apr 9, 2019 at 10:28 AM.
Tech Contributor
Joined: Aug 1999
Posts: 14,373
Likes: 6,371
From: At my Bar drinking and wrenching in Lafayette Colorado
Here is a list of issues that will prevent full throttle travel - from my Q-Jet paper available upon e-mail request:
A common problem is the issue of inadequate throttle cable travel. This is very common on Corvettes and Camaros. With a helper in the car and with the engine “off,” have the helper fully depress the gas pedal (with the engine hot and the choke wide open to assure that the lockout lever is disengaged). Observe the carb on the driver’s side and see if the secondary throttle moves to the wide open position: You can grab the throttle lever once the assistant has the pedal to the floor and see if you can move it further. If the gas pedal does not fully open the secondary throttle, you have one of several methods to fix this:
A common problem is the issue of inadequate throttle cable travel. This is very common on Corvettes and Camaros. With a helper in the car and with the engine “off,” have the helper fully depress the gas pedal (with the engine hot and the choke wide open to assure that the lockout lever is disengaged). Observe the carb on the driver’s side and see if the secondary throttle moves to the wide open position: You can grab the throttle lever once the assistant has the pedal to the floor and see if you can move it further. If the gas pedal does not fully open the secondary throttle, you have one of several methods to fix this:
- Remove your floor mat. I call this the “25 horsepower floor mat tuning trick.”
- Install the throttle cable in the correct position on the throttle lever. The Q-Jet has an “upper” and a “lower” cable attach hole: The upper hole was used for trucks and station wagons. The lower hole was used for Corvettes, Camaros and Novas. If you install a Corvette throttle cable in the upper hole, you will never achieve wide open throttle since there is not enough cable travel to open the throttle from the top lever location.
- Straighten your throttle cable attach bracket. The bracket that supports the cable at the carb is often bent slightly forward. If the bracket is bent or moved forward, it will not allow enough cable travel to open the throttle fully. Simply bend the bracket back just a tad: I use a big hammer and a steel rod to give it a whack. I call this the “25 horsepower hammer tuning trick.”
- Fix your gas pedal linkage. Very often, the actual steel linkage coming off your gas pedal will be bent a little “flat.” This will cause the pedal to hit the floor before the carb is wide open. You can give the pedal more travel by simply grabbing the gas pedal and bending it up off the floor. Care should be taken not to damage any plastic pedal rod bushings when doing this: Support the plastic pivot points when bending the pedal rod so the plastic bushings do not break.
- Fix the slop in the gas pedal attach lever. Many C3 Corvettes have a bit of wear on the lever that attaches to the gas pedal rod: The rod is "D" shaped, and the attach lever has a "D" hole with a screw tightening feature. If this "D" hole is worn, you can remove the lever, grind some material off the locking feature surfaces so it snugs up tighter, and re-install it to gain some travel
Last edited by lars; Apr 9, 2019 at 10:51 AM.
Is my vette stock?? HAHA
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After adjusting it, make sure the throttle still closes all the way too.
Thread Starter
Drifting
Joined: Nov 2016
Posts: 1,957
Likes: 576
From: Pittsburgh PA
so got a chance to work on it a bit last night. the issue definitely seemed to be at the pedal. heres the interesting thing, I guess early 68 has a different gas pedal
I assume this is a "normal" pedal:
https://www.ebay.com/itm/1969-1976-C...frcectupt=true
this is what I have under my dash:
https://www.ebay.com/itm/Corvette-Or...6cfa%7Ciid%3A1
I assume this is a "normal" pedal:
https://www.ebay.com/itm/1969-1976-C...frcectupt=true
this is what I have under my dash:
https://www.ebay.com/itm/Corvette-Or...6cfa%7Ciid%3A1
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,153
Likes: 9,279
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
so got a chance to work on it a bit last night. the issue definitely seemed to be at the pedal. heres the interesting thing, I guess early 68 has a different gas pedal
I assume this is a "normal" pedal:
https://www.ebay.com/itm/1969-1976-C...frcectupt=true
this is what I have under my dash:
https://www.ebay.com/itm/Corvette-Or...6cfa%7Ciid%3A1
I assume this is a "normal" pedal:
https://www.ebay.com/itm/1969-1976-C...frcectupt=true
this is what I have under my dash:
https://www.ebay.com/itm/Corvette-Or...6cfa%7Ciid%3A1
Last edited by Rescue Rogers; Apr 10, 2019 at 10:33 AM.
Pro
Joined: Sep 2016
Posts: 720
Likes: 205
From: Michigan
I had #5 from Lars's list. The bolt/clamp connection between the pedal and the D-rod was loose, and the slop was right there. Pedal was getting WOT when floored due to this extra slop at the start of pedal push. Tightened that up, found WOT, secondaries woke up, and re-gained my Hyper-Drive!
I must have posted this 4 or 5 times already, but I love sharing this one!
Love those cheap fixes!
Instructor
Joined: Nov 2018
Posts: 193
Likes: 70
From: Chicago
Lars... should my throttle linkage be on the lower hole (where the spring is attached)? This is my '68 with a 427 (not original carb). My kick down is not hitting the switch above the gas pedal (previous owner has a tube on it, but still short of moving the switch).
Tech Contributor
Joined: Aug 1999
Posts: 14,373
Likes: 6,371
From: At my Bar drinking and wrenching in Lafayette Colorado
As noted in my list above, Corvette must use the lower hole or you will not get full travel.
That's a commercially rebuilt Q-Jet, and is likely to have a ton of problems...
Lars
That's a commercially rebuilt Q-Jet, and is likely to have a ton of problems...
Lars