Hi!

First, i apologize for my, perhaps, bad english ...
You dont learn to much "mechanics" english at schools over here
in sweden, so there are alot of technical terms i dont now ...
If you dont understand something, please let me now, and i´ll
try to explain it better .. =)

Now to the problem ...

My Cadillac 429 has a really anoying problem, it doesnt run very well...

the car can one time go forever on idle, but the next time the engine gets to much fuel, it starts to "stumble" and just run on 6-7 cylinders ... if the car doesnt die, it keep goin´like that for a while,
but suddenly, just like flipping a coin, it goes perfect again ....
then it goes good for a time (could be seconds or minutes),
but it always falls back to the same bad behavior again ...
only runs on 6-7 cylinders and so on ....

it always run nice on higher rpm´s thou ...

i´ve had this problem for about a year, it comes and goes ...

These items has been changed since the problem started;
* Carburator (bought a factory remanufactured Carter AFB)
* The vacum timing advance unit on the distributor (brand new)
* Distributor cap, condensor, contact points, rotor cap, ignition wire´s and spark plug´s (brand new)

I have cleaned the ventilator valve which controlles the fumes
from the crankcase. It says in the shop manual that if the valve
is faulty it can affect the air-fuel ratio ....
I cannot get a new one, because the guy i buy all my Cad. parts
from is currently visiting the USA ... =)

I have try´d to adjust the idle mixture screws, but that did´nt
make any difference ..

I have´nt touched the idle air screw, could that cause such a
problem?

I also have a very leaky exhaust system .... goin to fix that soon ..

I´m really hopin´ that you guy´s can help me, or i´ll go crazy ...

Thanks for all possible tips or answers!

Throw the points in the trash where they belong and get a Pertronix electronic conversion unit. You may also want to check your fuel pump when the car goes to acting spooky, also check the sock in the fuel tank if need be.

Sounds electrical, I would check your wires over for crossfire between adjacent wires. Have you tried moving wires from plug to plug to try and move the problem to another cylinder?

__________________
Outlawed tunes from outlawed pipes

There is some trouble shooting you can do to help determine if it is a fuel or spark problem. Crank it up and let it run and stumble, recover and stumble again. Shut it off and pull all your plugs and look for wet, black plugs. If there are one or two, then it is most apt to be a spark problem. I they are all wet, I would suspect a flooding problem caused by a poor inlet valve /seat in the float chamber or a float set too high. This can be checked by taking the top off the carb, looking for a very full bowl and wet throat in the carb. If the float is riding very high, it needs to be reset in accordance to instructions, if it is riding low in high fuel, it could be a bad float or a bad needle/seat.

Trees

DoubleVision <- i have thought about buying a Pertronix, but i have´nt decided yet ... if the fuel pump was bad, would´nt it pump to little gas?

4 Jaw Chuck <- i´m gone isolate the wires, and switch between them ... thanks for the tip!

trees <- thanks for answering! i think that it has something to do
with the ignition ... it seems to be the same cylinder/s, the one in
front on the right cylinder row, and maybe the one in the back,
right row ..

a buddy ot mine sayes that if the engine goes down on the same
cylinder it can be the valve seal who is leaking ...
can someone confirm that?!

i think i´m gone change them anyway, they only cost 3$ for 16 o-rings.

I had a VW years ago that did that when one of the valves would stick open.

Fizz,

You have a tough one. I think it could be the gasket under the carburetor. Not that it is bad but the carb is loose and when it gets hot and then cold you draw in some air. I would try re-tightening the carb bolts. By the way what year is this 429 and does it have any smog devises on it like in the USA?

Keep us posted
Scholman

its a -64 .. no smog stuff ...

there is a gasket under the carb, and the metal gasket is there also ....