[BMWCSRegistry] Weber 38/38 vs Zenith 35/40

[M Thompson]

My only comment is that the Zeniths have a vacuum operated secondary 
throttle. The mechanical force on the gas pedal is constant as you 
push down. The Webers that I installed have a mechanical secondary 
throttle. The force on the gas pedal is OK until about half way. I 
then have to really push to get the secondaries to open. Not quite as 
smooth as the Zeniths.

I put an inordinate amount of time and parts into the Zeniths and 
never got them to behave correctly all the time.


At 02:08 PM 5/25/2007, paul.briggs at att.net wrote:
>I hate to ask this given the fact I have the Weber 38/38s on my 74 
>3.0CS, but, if both are in-tune, clean, etc, which performs better 
>across the full RPM range: Zenith or Weber?
>
>I've spent countless hours reading up on carbs, lots of $ with my 
>old mechanic, and at the end of the day (with an MSD ignition), my 
>Weber 38/38s on a stock motor idle very nicely, have tons of torque, 
>but absolutely no power above 4000 RPM.
>
>Sure, they're run up to 6,000, but it is slow going above 
>~4,000...the engine just runs out of air.   I'd love to have a 
>powerplant that had a nice pull all the way up the powerband, and 
>comparing the 38/38s, it would seem that the 35 / 40 Zenith is 
>better suited to provide some nice low end response (35 vs 38, so 
>maybe a bit less torque than the Weber), but at the top end the 40 
>vs the 38 allows more air, so you get a better top end, all things being equal.
>
>Has anyone drive a coupe both with Webers and Zeniths, both in good 
>repair, more or less back to back and could comment on how the 
>Zeniths delivery the power across the RPM range?   I suppose one 
>alternative is to just drop more modern motor with fuel 
>injection...but would my coupe have better power delivery across the 
>RPM range if the previous owner had rebuilt the Zeniths rather than 
>popping Webers on the car?
>
>- Paul
>
>'74 3.0CS
>'73 2002rtii
>'95 540i / 6spd - VERY NICE, AND FOR SALE (see listing on Roadfly)
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Michael Thompson