528 with Zenith carbs bucking

Falkenberg · Post by **Falkenberg** » Tue Nov 05, 2013 5:34 am

Jelmer wrote:It also includes thin gaskets to go between the bakelite spacer to prevent leaks.

That's a good thing. But double-check if the holes line up perfectly. The idle circuit passes through them and if the passages are partially blocked, idling suffers. I know that because at some point I made my own gaskets..

Mike W. · Post by **Mike W.** » Tue Nov 05, 2013 10:27 pm

Falkenberg wrote: I know that because at some point I made my own gaskets..

You're kidding! I thought I was the only one crazy enough to do that. However eventually I found the gasket material I used was porous enough that it really didn't work in that application.

Falkenberg · Post by **Falkenberg** » Wed Nov 06, 2013 3:41 am

No I am not kidding

I got quite handy at it at some point, but the material was indeed a problem. I used some thick (I actually have 3 sizes) paper like material that I ordered from Ebay. Easy to cut, good at the beginning but once you open the carb again you have to make a new gasket again.

Jelmer · Post by **Jelmer** » Mon Nov 11, 2013 5:37 am

Saturday I bought a acceleration pump nozzle. Let's hope this solves the problem!

Jelmer · Post by **Jelmer** » Sun Nov 24, 2013 6:48 am

Well, the E12 runs again and it pulls smooth thru the rpm's. But when you drive at a constant speed it is bucking real bad. I think it is because the carbs are not synchronised. Anyone knows how to synchronise them?

bizz · Post by **bizz** » Tue Nov 26, 2013 12:26 am

The Zenith's are tricky to sync i've been told.
http://www.e9coupe.com/forum/showthread.php?t=10942

Just ensure there are no air leaks where the two halves of the carbs meet, this will throw your mixtures out, and might also be the cause of your constant speed bucking.

Jelmer · Post by **Jelmer** » Tue Nov 26, 2013 2:29 am

bizz wrote: Just ensure there are no air leaks where the two halves of the carbs meet, this will throw your mixtures out, and might also be the cause of your constant speed bucking.

There are thin gaskets between the throttle plate-bakelite spacer-top part so the chance it leaks there is small but offcourse I will check it. I've ordered 2 vacuum meters and going to synchronize them. I'm on the E9 board to and already had advice from Steve.

Falkenberg · Post by **Falkenberg** » Tue Nov 26, 2013 11:32 am

I made a device myself from 2 identical GM MAP sensors. I connect them to the vacuum line that goes to the fuel return valves. That line is connected directly to the intake manifold under the butterfly so it should be somewhat related to the pressure there. Then I measure the difference of the voltage output of the 2 MAPs, which should be as small as possible.
I had reasonable good results with that.

I also bought a carburetor balancer that should measure air flow going in to the carbs, but the round nozzle did not match the intake of the carburetor so it was useless.

Jelmer · Post by **Jelmer** » Tue Nov 26, 2013 1:12 pm

I also bought 2 of these meters and 2 caps that fit over the entire carburetor. These caps have a 45mm hole in the top where you can fit the vacuum meter.

Jelmer · Post by **Jelmer** » Tue Dec 03, 2013 5:13 am

I worked on the carbs this weekend and the results where not that good. Yesterday evening I worked on them again and now they are balanced pretty good. I still need to do some fine tuning but it gets better and better.