rebuild Zenith carbs vs replace

[captainfixit]

Hello and Happy New Year.
I am Ted and a newly registered member.
After years of lustful desire, I finally obtained a 73 3.0 CS about 2 months ago and need to breath new life in it. I still have my E30 and R80RT as daily drivers. Does anyone have an opinion about rebuilding the Zenith carbs or going ahead and replacing with new Webers? Thanks.

 

[x_atlas0]

The stock Zeniths, by all accounts, do a very good job when in good trim. The Weber 32/32 is too small, and the triple 40's are not very good for a daily. (gas costs and whatnot) The dual 38's seem to be a good middle ground, although they apparently run out in the upper revs.

There have been a few people that converted their dual Webers back to the Zeniths.

Lately though, more people have been converting to Motronic than upgrading the carbs.

 

[velocewest]

Definitely rebuild. It's not a difficult job, the kits are available (Carl Nelson and Mesa Performance have them). Most important tip is to make sure the carb bodies have perfect, flat mating surfaces both top to middle to bottom and bottom to manifold. The throttle plate is the most common part to get a little warped. Lapping with fine sandpaper on a piece of glass will make them like new. As noted, Weber 32/36's are too small. 38/38's will deliver similar performance to the Zeniths but will cost you in fuel economy.

Also install a Pertronix Ignitor kit to replace the points. One of the cheapest, best driveability and reliability mods for an e9.

 

[jhjacobs]

I'm on of those people planning to replace my webers with zeniths. I picked up two rebuild kits and 4 zeniths and I am planing to build 2 good ones and have spare parts. They are pretty easy to find; they show up on Ebay from time to time and go for about $100-150 a pair.

I second the ignition upgrade notion. I dropped a kit into my coupe and I would never go back to points!

 

[m_thompson]

I spent a lot of time and $$ trying to fix the previous owner's attempts to fix the Zeniths. The lower castings were warped and the throttle shaft bushings were worn, so I gave up. I replaced them with a 32/32 kit from JAM. It runs great now, but there are some issues.

The secondary throttles on the Zeniths are vacuum operated. The gas pedal pressure is light, and is consistent through the whole pedal travel.

The secondary throttles on the Webers are mechaically operated. The gas pedal pressure is light for the half, then you really have to push hard to open the secondaries. Fortunately you can go about 75 MPH on only the primaries.

If I had a good set of Zeniths I would switch back in a second.

 

[E9WJC]

I have rebuilt 4 sets of zeniths in my time, and when done right you will not come across a better carby for the Bmw's. I have a e9 waiting to start resto it has been sitting around for 6 years now, and every time i give it a run all it takes is a slight press down on the gas pedal and it starts every time without any pumping of the pedal.

 

[NewSixCoupe]

I think its time to consider replacing my Webers with the original Zeniths; it takes at least half a dozen pumps to start the car...

 

[fhpete]

fjord/tan

Len,

I drove out to see Steve O'Neil last weekend as he was the one that posted my CS on the registry some time ago.

I'm a the proud owner of a 60k fjord/tan 3.0 that I'm told is an exact match to yours (so Steve says).

It is in for a zenith carb tune as I type (didn't pass original inspection for emissions). Hopefully they get it worked out. Other than that, it needs wood work.

I'll look forward to catching up with you sometime on a future sunny day.

Peter

Bernardsville, NJ