Accelerator cable/linkage adjustment
Thread Starter
Racer
Joined: Nov 2009
Posts: 384
Likes: 2
From: Tulsa OK
Accelerator cable/linkage adjustment
I noticed my throttle on my 68 is only opening about about 3/4 at the carb with the accelerator pedal floored.
The cable adjustment appears correct, in that there is no play or laxity at idle. The throttle begins to open immediately with any pressure on the pedal. It just doesn't have enough "pull" with full pedal depression to the floor.
I don't see any adjustment for this. The only thing I can think of is bending the lever at the firewall that attaches to the pedal rod (or buying a new one).
Any ideas?
The cable adjustment appears correct, in that there is no play or laxity at idle. The throttle begins to open immediately with any pressure on the pedal. It just doesn't have enough "pull" with full pedal depression to the floor.
I don't see any adjustment for this. The only thing I can think of is bending the lever at the firewall that attaches to the pedal rod (or buying a new one).
Any ideas?
Thread Starter
Racer
Joined: Nov 2009
Posts: 384
Likes: 2
From: Tulsa OK
Thanks EasyMike,
I did look at the AIM and all seems to be installed correctly. It's a fairly simple set up with the pedal rod going through a pivot post mounted to the firewall and attaching to a lever that accepts the end of the cable.
Just not enough "pull" on the cable even with the pedal on the floor.
I did look at the AIM and all seems to be installed correctly. It's a fairly simple set up with the pedal rod going through a pivot post mounted to the firewall and attaching to a lever that accepts the end of the cable.
Just not enough "pull" on the cable even with the pedal on the floor.
Melting Slicks
Joined: May 2009
Posts: 3,079
Likes: 314
2024 C3 of the Year Finalist - Unmodified
Thread Starter
Racer
Joined: Nov 2009
Posts: 384
Likes: 2
From: Tulsa OK
Yeah, I am concerned about breaking it by forcing it. I already did that to my kickdown switch.
Maybe I should by a new repro lever, they are available for $25-30.
I think I may take the assembly out of the car and work on it at the bench, if its not to tough to get out.
Maybe I should by a new repro lever, they are available for $25-30.
I think I may take the assembly out of the car and work on it at the bench, if its not to tough to get out.
Le Mans Master
Joined: Dec 2003
Posts: 5,727
Likes: 38
From: Fremont CA
Item is not hard to remove, there is a little plastic bushing holding the cable in, it pops out the back side (towards drivers seat.) Then there are two 5/16 or 1/4 bolt retaining pedal block to firewall. That's it your done!
Thread Starter
Racer
Joined: Nov 2009
Posts: 384
Likes: 2
From: Tulsa OK
Thanks SolidLT1,
sounds easy enough as long as can can contort myself under the dash and get my paws around the AC ductwork!
One thing I noticed is a pin on the lever that strikes a stop on the rod pivot bracket that seems to limit the travel of the lever. This may get in the way of my bending fix. Why the heck would that pin/stop be there?
sounds easy enough as long as can can contort myself under the dash and get my paws around the AC ductwork!
One thing I noticed is a pin on the lever that strikes a stop on the rod pivot bracket that seems to limit the travel of the lever. This may get in the way of my bending fix. Why the heck would that pin/stop be there?
Intermediate
Joined: Feb 2005
Posts: 37
Likes: 0
From: St. Peters Missouri
I recently did some work on my 69 / 427 to see why the carburetor throttle linkage would not move enough to kick in the carburetor secondaries. After removing the seat and steering wheel so I could get at the gas pedal. I found that someone had installed the lever that attaches to the gas pedal backwards. The 68 and early 69's used a different setup than the later cars. After turning this arm around, I picked up about an additional 1-2 inches of travel. I ended up finding a good diagram of the early gas pedal setup in one of my Paragon catalogs. My assembly manaul only showed the setup for the later cars with the different setup. I am not sure what is shown in the 68 manuel but I would assume it would be correct.
My fix was as easy as turning the arm around. The tall part of the arm goes to the right of the car when installed on the pedal.
70 MUSL
My fix was as easy as turning the arm around. The tall part of the arm goes to the right of the car when installed on the pedal.
70 MUSL
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Thread Starter
Racer
Joined: Nov 2009
Posts: 384
Likes: 2
From: Tulsa OK
70 MUSL
I think you may have found my problem!
I looked at the AIM again and it does look like the lever on mine may be installed backwards. The "tall part of the lever arm" is towards the left of the car, while the short secition is facing the right.
If this turns out to be it I owe you a virtual 6 pack (heck a whole case!)
I think you may have found my problem!
I looked at the AIM again and it does look like the lever on mine may be installed backwards. The "tall part of the lever arm" is towards the left of the car, while the short secition is facing the right.
If this turns out to be it I owe you a virtual 6 pack (heck a whole case!)
Tech Contributor
Joined: Aug 1999
Posts: 14,376
Likes: 6,375
From: At my Bar drinking and wrenching in Lafayette Colorado
Inadequate throttle travel is the most common performance problem I see on C3 Vettes. I'd guess that at least 75% of all the C3s I've worked on do not achieve wide open throttle due to linkage problems. The #1 method of fixing this is to remove the floor mat: I call this the 25 horsepower floormat tuning tip...
There are 4 other things you can do to correct the linkage travel problem:
Lars
There are 4 other things you can do to correct the linkage travel problem:
- There are 2 attach points for the throttle cable on the carb's throttle lever: One hole towards the top of the lever is for trucks and station wagons. The lower hole is for Vettes and Camaros. If you install the Vette cable in the upper hole, you will never get enough travel. Move the cable to the lower of the 2 holes.
- Many cars have an incorrect or bent cable attach lever on the carb. In many cases you can simply bend (by hitting it with a BFH, as toddalin has me doing in the photo above) the lever a little back and proper travel will be achieved.
- Many C3s 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.
- Finally, most C3s have a bent accel pedal rod. To correct this, you can simply grab the gas pedal rod and bend it upwards to get the pedal up off the floor. You have to do this with some discretion so you do not break the nylon bushings out of the rod attach point. By bending the rod upwards, you can get as much pedal traval as you need and want.
Lars
Last edited by lars; Apr 2, 2010 at 11:07 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
And, once you get 'full travel' of the throttle cable and linkage, you can then make certain that the carb is operating properly and that it allows the secondaries to actually open! (curious as to what percentage of C3's have this malady....)
Tech Contributor
Joined: Aug 1999
Posts: 14,376
Likes: 6,375
From: At my Bar drinking and wrenching in Lafayette Colorado
Good point. On a Q-Jet, there is nothing that can prevent the secondaries from opening if there is full throttle travel, except an engaged secondary lockout tang. The secondary lockout tang is intended to prevent opening of the secondaries while the engine is cold, thus preventing engine damage. However, if the choke is not adjusted correctly (and many aren't), it is not uncommon to see that the secondary lockout tang never fully retracts, and keeps the secondaries locked out under all conditions. It's always a good idea to check this on a hot engine: With the engine hot and shut off, have someone in the car push the pedal to the floor. With your fingers, push the secondary airvalve open and look down the secondary venturies. You should be able to see the secondary throttle wide open. If they are wide open, the secondaries are working. If they're not, you have a little adjustment work to do...
Lars
Lars
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 98
From: Ontario
Lars,
Re your #1, here is how not to do it....:o Not to mention the valve covers on the wrong side. Not to mention ported vacuum. That was two years ago. All is well now.
Re your #1, here is how not to do it....:o Not to mention the valve covers on the wrong side. Not to mention ported vacuum. That was two years ago. All is well now.
Last edited by Paul L; Apr 3, 2010 at 12:12 PM.
