edelbrock 7094 linkage

[benno440]

just following the instructions of the edelbrock linkage and it says to set the 1:1 linkage while holding both dual qquad carbs at WOT.
I do this and then release the butterflies back to closed and the front carb doesn't fully close as the back carb is keeping it open.

does anyone know what might be causing this? I am guessing this might be my dieseling problem.

 

[Meep-Meep]

Go back and read my old post about setting up the linkage. Basically you need to have both carbs doing the exact same thing. That means each throttle lever must start from the same spot, so back off both idle speed screws until the blades seat in the bores then hook up the linkage. Also you need to make sure to adjust the linkage to compensate for any slop. And to test the operation apply force from where the throttle cable would pull from. Attention to detail is very important here.

 

[benno440]

where can I find that post meep?

 

[Meep-Meep]

Hell, I don't know. I replied to one of your carb tuning posts a while back. Oh wait!! There is this new feature that lets me search old posts. Lemme see if I can find it.

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OK, that search is for posts that I started. Go up to "find your threads" and look in there.

 

[benno440]

sorry meep i cant find it, been through every post, maybe it was someone else you replied to? come to think of it this is the first time i have asked about the linkage.

i guess i will tinker away to find what works.

 

[Meep-Meep]

I remember giving a long dissertation about setting up the carbs when you first started playing around with them. Anyway, what you want to do is back off the idle stop screws all the way until the blades seat in the bores. Then attach one end of the linkage to one carb and adjust the length until the other stud or bolt slides in without influencing the other throttle arm. Once the linkage is connected to both carbs do a test pull from where the cable connects and watch both carbs using peripheral vision. You need to make both carbs begin to move at the same time and make the necessary rod adjustment to deal with slop in the ball ends or pivots so things work in unisyn. This sounds **** as hell but in my opinion it's the best start at getting good low speed drivability with multi carbs. Once both carbs are in complete sync check the WOT. If you are 1/32" away from fully open on one or both carbs I'd leave it alone or adjust the connecting link between the primary and secondary bores. You won't see a difference if the secondaries on one carb are 2 degrees from open.

Once the linkage is set move the idle speed screws until both throttle levers make equal contact and rest with equal pressure on the screws. This is how things stay in tune. As far as a setting goes, about 1 turn from seated might be a good start. Mixture screws should be initially set with equal precision - lightly seated then out the same amount of turns. Once it's running idle mixture adjustment will need to be set with a good ear finding the lean drop on each screw and where they end up is what it is.

If you really want to get crazy you can use my Porsche carb or MFI setting method that I actually developed when I rebuilt the carbs on my buddies Honda CBX. This method is really worthwhile on an individual runner setup but probably not needed when the carbs are somewhat tied together by a plenum. You have a lot more forgiveness in the plenum setup.

 

[benno440]

thanks meep,

at the moment the linkage is set at both throttles closed and both synced, when at wot the front carb probably still has 2* till 100%open when the back one is 100% WOT.

do you have any knowledge on adjusting the connecting rod to make the front one open that slight bit more?
also both tie rods on the linkage are connected to both 1/2" holes on the carb throttle brackets whereas i have seen some pics where the back carb uses the 1/2" hole and the front carb uses the smaller hole, i wonder if this changes anything.

attached is pics of what i mean. top pic is how i have it bolted on bottom pic is the other way and i am unsure if this maakes a difference as the throttles go through the curve?




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that top pic is not my setup only a pic i found, that shows which bolt holes i used, mine is actually at 1:1 setup wwith no slop like this one has

 

[Meep-Meep]

I didn't actually look up that linkage P/N but I see what you mean now. The one above is a progressive set up, or I suppose it can be 1:1 if you move the stop.

For the 1:1 application you want both attachment points to be on the same holes to keep the ratio the same. By ratio I mean the distance the hole is from the throttle shaft should be equal on both carbs. If your cable pulls on the rear carb throttle arm, and that arm pulls the linkage that moves the front carb, you will have to eliminate some slop in all the connections so the front throttle doesn't lag behind. I suspect the rear throttle arm is moving before the front because of the tolerance stack up in the linkage attachment points, and that is why you are not getting WOT on the front carb. In short that means the carb linkage is not synched. Again, use your peripheral vision to look at both carbs while you move the cable to see how much you need to adjust the linkage until the front carb picks up as soon as the rear carb throttle is moved. It will be tedious but in the end a properly working set up.