38/38 Carbs

TedS

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how would that manifest?
From zero to part open throttle I have to push really hard so smooth shifts are difficult. Much stiffer than the 32/36's I removed. Just curious is this is common. I thought I read this on another site where they were replacing single 32/36's with 38's.
 

Dick Steinkamp

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From zero to part open throttle I have to push really hard so smooth shifts are difficult. Much stiffer than the 32/36's I removed. Just curious is this is common. I thought I read this on another site where they were replacing single 32/36's with 38's.
My Bav came to me with 38/38s. My linkage has always been progressive and smooth. I did adjust the idle screw and the chokes to spec. Also, when I hooked the advance side of the dizzy direct to manifold vacuum (and set the idle speed back down) and disconnected and plugged the retard side and the ported vacuum ports in the carbs. it eliminated the remaining bit of off idle hesitation.
 

Stan

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From zero to part open throttle I have to push really hard so smooth shifts are difficult. Much stiffer than the 32/36's I removed. Just curious is this is common. I thought I read this on another site where they were replacing single 32/36's with 38's.
I have 38/38 Webers and my linkage is progressive and smooth as well. As you see my car has; 3.5L, short shift, 5 spd, light flywheel, LSD, Weber 38/38, 10.5:1 pistons, Paul Burke cam, Stahl headers, 1-2-3 Ignition and was dialed in by Vintage Sports and Restorations
 

TedS

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This is good to know. I seems like my linkage is smooth and easily articulates when disconnected from the carbs, though. Maybe it's that they're weber copies, but off the car twisting open the butterflies meets stiff resistance from the return spring-- double that for dual carbs and it's really hard to smoothly take off from a stop.

My other two cars, one with modern injection and one with dual SU's, have much less resistance. Unless the BMW is all I drive I'll never get used it.

Some Moto Guzzies have really stiff return springs in their Dellortos and luckily replacement springs are available. I replaced the springs on the 38's with genuine ones and while the tabs were clocked slightly differently they are just as stiff.
 

pickman

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When I converted to a 3.5 L so too the 38/38 using the stock linkage. Had to play around a lot with the adjustable plastic/metal links to the carbs as they appeared to be under center making it hard for the carb linkage to pull up. It had nothing to due with the spring. Had to modify the holes on the linkage that runs along the engine moving them inboard for both carbs. After more tinkering I solved the kinematic puzzle.
 

TedS

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Thanks for the replies. Reading them encouraged me to quit looking at the springs- It was the linkage!
The bell crank wasn't resting on its stop at closed throttle. I loosened the arm up at the rod and the bell crank spring snapped it back into place. It either slipped or, like Mr. pickman, the engine swap caused things to be slightly off. Now smoother throttle.
Thank you!
 
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