Technical Problem with Strom 97 butterflies wont close completely when running

Maybe someone has an answer...Have a couple of nice, rebuilt 97s on a basically stock 59A. Just converting from a couple of 48s. They both test good, running individual, but when I hook them together, the vacuum tends to not allow the butterflies to close all the way. If I shut off the engine, they will usually close all the way. I have added an extra return spring and that helps somewhat. It idles at about 600 rpm but when I hit the gas, the idle will not come down below 1000 rpm until I turn off the ignition. No binding in linkage. If I disconnect the accelerator pumps, its a little better, but not much. Thanks for any help/suggestions

 

The butterflies in my dual Stromberg setup never close all the way. Got to be open a little or you won't get anything through for it to idle on.

If you had a 3-2 then you would need the outers to close all the way.

 

Usually its what engineers call 'tolerance stacking' ... Where you are trying to pull one carb back to idle through all the linkages, and all the little bits of slack add up and mean one carb wont fully return. the little stromberg return springs arent really strong enough Ive found, its probably a matter of adding a second return spring, one pulling on each carb.

 

I figure that is probably what is happening. Will give the spring thing a try. Tks

 

Also, take a bit of time and synchronise them and make sure they are closing at the same time and rate. Borrow or buy a Sync, take the linkage off between the carbs, set then the same, then hook the linkage back up and make sure each carb stays the same. If not adjust the linkage.

 

I see you have the extra return springs on the two throttle shafts on the side tying the two carbs. together. If you move the linkage slightly more vertical there will be more spring pressure at the closed throttle position. Uncle Max also has HD springs for the accelerator fulcrums. I had to have both sets of springs on both carbs. Do the two carbs return to the same idle with the linkage from the carb to the firewall linkage disconnected? Is the spring on the firewall linkage in good condition and is the firewall linkage very free, clean & lubed. also place a small bit of light grease on the ball connection points and their linkage sockets, including the short rods on the throttle to fulcrums.
By the way how does the engine run? What size mains and PV???

 

My thinkin is PV is opening raising the idle . May need to change power valves , to help the issue

 

Thanks needlouvers...They close exactly the same. appears the vacuum is holding them open a bit because
when u turn the ignition off, they close completely then...48-760 suggested adding more spring. I will try that

 

Thanks 48-760 i will contact UMax and see about the springs. The carbs work great accept for the last little bit of closing...They WILL close after ignition is off, so suspect vacuum is helping keep them open a small amount

 

Vacuum would tend to CLOSE the butterflys in my opinion,not make them stay open slightly

 

If the mechanical advance weights in your distributor don't return properly to idle position, due to being crusty or if the return springs are weak, it'll do the same thing.

 

Strombergs have manual power valves that only open under nearly full throttle when the accelerator pump shaft bottoms out.

 

Yeah, I'm not getting the root of this problem. How can a carb close all the way and still idle? You do not want them to close all the way, unless one of them is part of a progressive system.

Start you car up and take two long screwdrivers. Push the butterflies closed all the way and see what happens.

 

The throttle plates are not closed all the way at idle. The idle RPM adjustment screw will set the idle plates somewhat open. You would have to screw the idle level adjustment back until it did not touch the throttle linkage to get the plates completely closed. At that point the engine would most likely stall from trying to idle at extremely low RPM. I believe Sttromberg has a preliminary setting on the screw of about 3/4 turn open from first touch.

 

If you can help the linkage return to idle, manually, and the idle level is then consistently at the RPM adjustment you want it would appear the problem is slight sticking of the linkage. From your photo it would appear your car does not have many miles. New linkage can have some minor inherent binding this may disappear once you get some miles on the car. The addition of HD return springs can help get through this break in period. Once you get this idle problem straight do synchronize the Carbs.

 

I will check the sticking linkage...Everythin worrked great with the previous carbs. I will lube everything up real good and check for binding. Engine runs great, i am hoping i can just get it to return to actual idle when i let off the gas. I think Uncle Max HD return springs may work. Will give him a call...Thanks for all input.

 

Did you ever figure out what’s going on? I’m having the same exact issue with 2 97’s on my 59A as well.


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Ever figure this out?


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I’m having the same exact problem with my 97’s and I’m stumped.


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