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Dual DCOE Throttle Bind When Hot


ericbrown

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Hey guys,

 

I recently bought and installed the dual weber DCOE 40 kit from redline, but I am having a problem with the throttle binding when the car is hot.

I can drive the car normally from a cold start with an idle around 1000rpm, but after driving it around for awhile on a hot day, the idle will start to hang at around 1500-2000 rpm. If i pull the linkage up by hand, the idle will go back to normal.

 

According to Redline, over-tightening the throttle shaft nuts are a big cause of problems, but i double checked mine and they are tightened to just a little bit past finger tight. When I first swapped the redline throttle lever over, i did over-tighten the nuts, which caused the throttles to bind, but I backed them off and tried again and the throttles opened and closed smoothly after that.

 

I tried disconnecting the linkage from both carbs and manually pushed down on the throttle levers, and both carbs bind before reaching the idle stops when hot, so I don't think it is a linkage problem. If I leave the car overnight, everything works fine the next morning until it gets hot again.

 

I'm not sure if I screwed the throttle shafts up somehow by over-tightening them originally, anyone have any ideas?

 

Also, pics:

 

 

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I could probably say this in a more diplomatic way, but I hate those linkage rod style linkages. Centerpull is a vast improvement and eliminates all of the issues found with the stock style linkage.

 

Search "centerpull linkage" on here and you should find a couple threads with good info.

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I also have this issue sometimes. Very intermittent though. For now I've resorted to a larger return spring. I'm not very happy with the long rod setup and im going to get the center pull kit. When I get it im going to pull the carbs off and see if I have bent shafts or if they're rubbing the butterflies in the throats. Also if you have your collars set too tight on the rod ends the rod ends will bind. This also caused my throttle to hang a few times.make sure that rod can move back and fourth a hair.

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Yeah, I figured out pretty quickly when i was trying to adjust the linkage rods to be the same length that this linkage style sucks. I might upgrade to a cable linkage in the future, but I wanted to take care of any binds that might be happening in the carbs themselves first.

 

I contacted Redline and they suggested I loosen throttle shaft nuts half a turn, and then use a small rubber mallet on the throttle shaft end to try to recenter the throttle shafts, until i get them to a position where the throttle opens/closes the easiest and smoothest. I have to take the carbs off to do that though, so i'm going to give that a shot this weekend I guess.

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  • 4 months later...

I got this issue resolved awhile ago, but I finally had a chance to test it under the same conditions to make sure the problem was really solved.

 

I followed Redline's instructions for checking and fixing throttle shaft binds, but I didn't really find anything wrong there.

 

I ended up switching to a center intercouple linkage and adding an additional return spring directly to one carburetor, both from Pierce Manifolds. I then re-sync'd the carbs with a synchrometer.

 

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I've since used the car during 90 degree days around town, and I did an autocross at Auto Club Speedway last weekend in 80 degree weather. So far, no more binding issues and the carbs are working well. I did run into an issue with a stuck float, so I went ahead and checked and re-set both float levels. The one that got stuck was like 3mm off of the other one.

 

Thanks for the help, guys.

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So you're using a centerpull coupler but still the linkage rod assembly? Two rods or one? If two, then what's the point of the center interconnect? If one, then you run the risk of bending the first throttle shaft, unless the rod is in between the carbs connected to the centerpull linkage.

 

Part of the reason the cable linkage works so well is because it eliminates the monkey-motion firewall linkage bellcrank setup. Lots of binding at the bellcrank not to mention engine rocking induced throttle action.

 

Do you have pics of the final setup?

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I'll take a new pic later, but it's a single rod connected to the side of one carb. I have 2 of the male throttle levers for the centerpull linkage, one with the ball pin for a rod, the other for a throttle cable, but the rod one didn't work in the center due to the spacing of the carbs plus rod interference with the female side at full throttle. So I ran the throttle lever on the side.

 

I'm going to switch to a throttle cable soon, rather than try to modify the rod throttle lever to work in the center, because it still has all the rod linkage disadvantages you mentioned, I just need to buy the cable and mount. Running it this way for now because I needed the center linkage anyway and I already had the other parts. Right now I am happy that it is not binding up at idle anymore, but it should be even better with the cable. The engine rocking at idle being transmitted back to the gas pedal is kind of annoying.

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