Carb throttle linkage? - Team Camaro Tech
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post #1 of 12 (permalink) Old Apr 11th, 11, 06:45 AM Thread Starter
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Bruce
 
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Carb throttle linkage?

I have a 770 Holley on top of an Edelbrock Air Gap manifold. I am using a 396/375 HP throttle linkage and it only opens the carb about 50% on my 69 Camaro. Any ideas on what linkage to use? I have adjusted the linkage as far as it will go. Its like have a 2 BBL. Drove the car for the first time 100 miles on the highway to Lowes Autofair and used 13 gallons of gas!!!!!! 3000 RPM at 60 mph
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post #2 of 12 (permalink) Old Apr 11th, 11, 08:28 AM
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Re: Carb throttle linkage?

Do you have this?

http://cgi.ebay.com/ebaymotors/1967-...item1e6259e4fb

Jeff G.
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post #3 of 12 (permalink) Old Apr 11th, 11, 08:32 AM
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Re: Carb throttle linkage?

First question I'd ask is if the linkage is hitting something and creating an artificial stop. Look for plug wires in particular that often seem to route exactly where the linkage is. Next thing to check is if the rod from the pedal itself is bent.

My 68 is the standard mechanical linkage and the portion of the linkage inside the car from firewall to pedal was bent and had to be replaced so I could get WOT. I also replaced the ill fitting rod that attaches to the carb with a threaded rod and heim joints just so I could take all play out of it.

Russ (RJ)
The Garlic Capital, Gilroy,CA

(sold June 15,2014) 1968 RS convertible that is not quite stock

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post #4 of 12 (permalink) Old Apr 11th, 11, 08:41 AM Thread Starter
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Re: Carb throttle linkage?

That is the one that I have. There is no obsruction when the rod is pulled back towards the firewall. I will check the pedal mechanism.
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post #5 of 12 (permalink) Old Apr 11th, 11, 11:50 AM
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Re: Carb throttle linkage?

I remember something about the reproduction Holley carb throttle arm being longer than the original. Also where are you mounting the arm to the linkage on the carb? Make sure your gas pedal, the linkage and arm on the firewall are not causing the problem. If you don't care about originality you could do something like this...

https://www.camaros.net/forums/blog.php?b=153

Hey since you mentioned the 100 miles on 13 gals, you do realize that will get worse if you get the secondaries to open up! What engine do you have? It sounds like you have some tuning issues along with a linkage problem.

...Dennis

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post #6 of 12 (permalink) Old Apr 12th, 11, 05:46 AM Thread Starter
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Re: Carb throttle linkage?

The only original thing on my car is the body! I have the linkage hooked up where the spring is on the example pics. It seems like I need a longer rod, like a small block rod. Your are right about getting it tuned up. I cannot even see the line on the HB to get the timing right. The car also jerks when I am crusing in any gear at any speed. Two of me mechanical buddy's can't figure this out. At first we noticed fowled out platinum plugs from just starting and moveing, but not driving the car yet. We put some stock AC, 45's in and that helped a bit. The thinking now is the valves may be too tight and take them down a 1/4 turn. As you can see I have a few issues to deal with. Having said that we took best in class at the show and the car looks great! Any more suggestions would help. The engine is a 72 LS5, bored to a 468 with a comp X-treame 286/556 cam, if I remember right.
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post #7 of 12 (permalink) Old Apr 12th, 11, 09:52 AM
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Re: Carb throttle linkage?

Bruce if you are only getting part throttle then you need a shorter rod not a longer one! Also using the hole that my return spring is in for the throttle rod will make the gas pedal more touchy because it's closer to the throttle shaft itself.

You'll need the help of a buddy, with the engine off have someone floor the gas pedal and hold it there. Now see how much throttle is left by manually operating the throttle at the carb.

If you can move the throttle further open the problem is in the pedal and arm assembly at the firewall.

If the throttle arm is hitting the firewall that tells you the rod is too long...

Be careful though if you make any changes be sure the throttle close all the way before ever starting the car, it's important that the throttle closes properly!.

...Dennis

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post #8 of 12 (permalink) Old Apr 12th, 11, 07:18 PM
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Re: Carb throttle linkage?

Quote:
Originally Posted by DjD View Post
Be careful though if you make any changes be sure the throttle close all the way before ever starting the car, it's important that the throttle closes properly!.
Haha, this is kinda funny because once, years ago... I made some mod to get the secondaries to open on the 427 in his 69 Truck. It worked in my mind... but it hung em wide open. Oops!!

One thing I've done before is to take a die and cut more threads on the throttle rod. I think it's 1/4" coarse thread. "In theory" that makes it shorter so you'll get more range of motion. As long as it allows it to close back down all the way.

Sounds like it needs some tuning. But then again, 8mpg might not be out of question with so many cubes and no overdrive. That's what my silver car gets and it's pretty tame. Congrats on winning class, send or post some pics.

Driving a #s-matching Z in the rain..... and lovin' it....
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post #9 of 12 (permalink) Old Apr 13th, 11, 05:40 AM Thread Starter
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Re: Carb throttle linkage?

Hey Dave, You would think I would learn from the 427, but I have slept since then. I will fool with the issue this week end. Then I will work on the AC as the radiator hose is touching the compressor, thinking of having a curved neck installed to clear everything. Later, Dad
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post #10 of 12 (permalink) Old Apr 13th, 11, 06:21 AM
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Re: Carb throttle linkage?

Ever thought of converting to the Camaro cable system instead of the rod?
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post #11 of 12 (permalink) Old Apr 13th, 11, 09:04 AM
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Re: Carb throttle linkage?

Quote:
Originally Posted by mahunt View Post
Ever thought of converting to the Camaro cable system instead of the rod?
I have a Nova with the factory cable from the pedal to the carb and it's nothing but a pain in the gas. I will gladly replace it with hard linkage like that on my Camaro when I get the opportunity.

The biggest problem with the stock cable assembly is Chevy used several different length cables and the reproduction market sells one size fits all. Then when you use non factory carbs and intakes it complicates things even more. Don't take this wrong, I was able to make the cable work in the Nova but the hard linkage was much easier to deal with in the Camaro and the pedal feels far more positive.

The expense of a new pedal assembly and cable in order to use a cable isn't really worth it either if you already have the hard linkage.

...Dennis

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post #12 of 12 (permalink) Old Apr 13th, 11, 09:52 PM
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Re: Carb throttle linkage?

Lokar!

By profleetline at 2011-04-13

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