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  #1 (permalink)  
Old 05-27-2010, 07:26 AM
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Cobra Make, Engine: BDR#499 351W with Webers
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Default Center Pull Linkage 351W

I know there are some other threads with a similar theme active right now, but I am looking at doing something a little different…

I have a 351W equipped with a manifold that does not have the center boss cast in to facilitate the mounting of a center pull bell crank. Consequently my Webers are actuated by a side mounted bell crank attached between the two left carbs. The right hand bank is actuated by a rod connected from the left rear carb to the right rear carb, which is linked to the right front carb via a synch screw. (see my photo gallery for the install)

This setup is NOT ideal and is, in my opinion causing undue torque being applied to the throttle shaft of the right rear carb. I currently have the right rear carb removed to attempt to straighten the twisted throttle shaft.
What I would like to attempt is to keep my side mount throttle (changing the cable looks to be a big hassle) and actuate all four carbs from the side mount, but actuate the right bank from the center, rather than the rear.
What I think might work is to mount a longer throttle lever on the left rear carb (center position) with two holes in it. I could then attach the bell crank rod to the lower hole and install a second rod in the upper hole which would actuate the reversed (upside down) throttle leavers of the two right bank carbs.

What I don’t know is if this has been done before, or if anyone is running something similar. If so it sure would make things a lot easier to know how they did it. I am sure I could figure out the geometry, but if I don’t have to and can just purchase the needed parts, I of course would rather do it the easy way.

Of course I may be way off here, too. If so, or if you have a better mouse trap, please let me know!!

Thanks,

Gun Doc
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  #2 (permalink)  
Old 05-27-2010, 08:14 AM
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I'm trying to visualize your plan in my head. Frst, you can't use a longer lever, and attach one rod to one hole, and another rod to a differant hole higher up. That changes the range, and your balance would be off. It's really critical that all levers and attachement points be exactly the same.

If I understand yout linkage arrangement correctly, there's nothing wrong with it. That's not your problem. If the throttle shaft is twisted, something is binding inside the carb. You have to find and fix that problem. Don't waste any time or effort changing the linkage.
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Old 05-27-2010, 10:57 AM
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I just got off of the phone with Chuck at Inglese and he got me all set up. They do make a side actuated center pull linkage. It uses the 1 to 5 side bell crank with a driving rod that attaches between the upper holes on the levers on the two left carbs. It also has a second rod sandwiched between the same levers (left side) that actuate a reversed lever (upside down) on the right bank.
I have to disagree with you, Bob on my setup not causing problems…The left rear carb throttle shaft is handling the torque created by both carbs on the right bank. The two right hand carbs are linked together at the center point with a synch screw. The two carbs in combination are being driven by one rod attached to the lever located at the rear of the right rear carb, which is being driven by the input at the front of the left rear carb. That carb (left rear) handles the force of all the springs on three carbs, plus any other residual force cause by friction and, or heat in the linkage.

A center pull system effectively reduces the force felt on any one carb to that carb alone.

I do have the carb off and there is no binding in the carb, but the throttle shaft is twisted.

Gun Doc
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Old 05-27-2010, 02:16 PM
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Oh, I see. I pictured it differant in my head. You're right, the center pull will eliminate that problem.

Mine was set up as a side pull. It worked pretty well. But I made a smidgen more power with a center pull. I suspect the side pull cause a little imbalance in the upper throttle ranges, because it pulled out of the corners better.
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