Dual 94s one really sucks, one not so much

R

RandyMettler

Senior Member
I have dual 94s on a 8BA. When pulling the air cleaners off the carbs with the engine running, one has a strong sucking sound while one has a barely audible sucking sound. When covering either of the carbs with my hand, one at a time, it kills the motor. I would think the carbs would have equal sucking sounds. To me, this is an indication of a problem with one of the 94s.


I did a propane test to both 94 with no increase in rpms.


Also, when cold and throttling the gas I get misfires. When the engine warms up after 2 minutes I get smooth throttle response. To me, this in an indication of a vacuum leak sealing itself with thermal expansion. Is it possible that a weak coil takes time to warm up to provide consistent strong spark? (I know far fetched)


Any thoughts?


Sorry about multiple post, I am just trying to work through my current problem
 
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Try a Uni Sync to get the vacuum correct.


Do both have chokes on both carbs?


Cold and throttling could just be fuel not firing in the cyclinder. Let it warm up before throttling.
 
Tinker,


Thanks for all your help.


The primary only is set up with a choke. The secondary toward the front of the motor, is the 94 with the strong sucking sound, no choke. It is much stronger than the primary carb, mounted closest to the firewall.


Do you have a favorite uni sync manufacture?
 
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Randy,

Look into the air horn and see if both carbs have identical nozzle bars. If OK
there back off the idle SPEED screws so both the carbs are 100% shut, with as sensitive a touch as you can conjure just barely crack the throttle open on each carb. From the just barely cracked setting advance the idle SPEED screws in 1/4 turn at a time until the motor idles where you want it. At this point if your problem is still with
you a UniSyn will help with adjusting the mixture screws. The alternative is to run each carb individually maybe on the buddies single carb motor and set the idle MIXTURE screws that way.
Charlie
 
Tinker, No I don't have progressive linkage and understand with dual setup you should not. I am running Charlie Price dual 3.5 power valves and 47 jets.


My 94s are not identical. The primary chocked 94 has what I am going to term as a float bowl vent tube located in the center of the air horn. The secondary 94 has a float bowl vent hole, factory drilled in the side of the air horn. I think both accomplish the same function but could be wrong. If you would like pictures I can post tomorrow.


Not sure what "nozzle bars" are, both carbs are identical with the above acceptation.


And thanks Charlie, I sent a check to you today for one of your fuel pumps. Mine is not rebuildable. I am getting fuel in my oil and am tired of changing my oil through this diagnostic proocess.
 
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Have you tried what charlieNY suggested?

Run the idle screws in and set. What the uni-sync is for.

pv and jets seem right on the ballpark mark.

Duels take some time to setup.... and multi carbs always need to be revisited.






.
 
Talkwrench



"disconnect the carbs from each other when tuning , re connect after you've finished. And check."


Do you mean remove the fuel supply from one carb at a time when adjusting?
 
Tinker,


When you say "block off the carb port" do you mean the fuel supply to each card individually?


I will try Charlies advice tomorrow. I worked on the car all day, so need to recharge the brain and bones. Oh, and by the way, the alumaseal has seemed to work. I'll see tomorrow.
 
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It's a conversation, anyone can pipe in. We all solve problems together.

Carburetor "intake" port.




.
 
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I'm curious, what distributor are you using. The stock one won't work right. Just another problem.
Gramps
 
Isn't it common knowledge that you should leave the choke mechanism in the secondary carb, even if it is not hooked up or used? When the mechanism is removed, it screws up the airflow in the carb.
 
Tubman is right. You want the choke plate in there. Also I think 47 jets are too small. I would think 49 - 51 unless you are at a high altitude.
 
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