carbarator idle problem -- help !

[thomaswat]

I can't seem to make my engine in my '65 ( rebuilt original 350hp ) with an Edelbrock 650cfm carb, idle properly. Sometimes it seems to be o.k., but other times with the idle set around 750-800rpm it will run for around a minute-more or less- and them just die like it's out of gas. If I bump the gas to keep it from dieing, it speeds up just fine, but in a minute it starts to die again. It doesn't happen every time, but more often than not. I try adjusting the screws on the carb and sometimes turning them just barely will help, but next time I drive it, it starts doing it again. The carb only has around 500mi. on it. This problem started after the engine was rebuilt. Lastly, if I set the idle speed to around 1100 or so, I doesn't seem to do it.
Tom

 

[IH2LOSE]

Welcome to our forum I am sure youll get some recomendations.

I am not familur with your carb,But I will suggest you maybee cover the horn of carb (trying to smother it while racing the motor) some times the idel circut has a tiny blockage in it and the vacum from smothering the motor is enough to pull it out,

Good Luck

 

[JohnZ]

I try adjusting the screws on the carb and sometimes turning them just barely will help, but next time I drive it, it starts doing it again. The carb only has around 500mi. on it. This problem started after the engine was rebuilt. Lastly, if I set the idle speed to around 1100 or so, I doesn't seem to do it.
Tom

You can't just "adjust the screws" - the idle mixture needs to be set using a vacuum gauge, connected to full manifold vacuum, and adjust both idle mixture screws (back and forth) to achieve the highest steady vacuum reading; until you do this, your idle mixture won't be correct, and the idle will be unstable. Also a good idea to set the dwell (first) and the timing while you're at it, verify that your vacuum advance is working, and check for vacuum leaks, fouled plugs, bad plug wires, etc. - a complete basic tune-up.

 

[thomaswat]

I had just set the timing (rebuilt engine) when all this started. I was just messing around with the carb a few minutes ago, and instead of the engines just quiting, it actually will drop from around 900rpm to about 450rpm and just sit and chug. I wonder if the vacuum advance just gradually drops out- slowly loosing vacuum unless the rpm is higher ? I have the correct vacuum cannister according to NAPA. It is made for the 350hp engine. It seems like I tried it with higher rpm, and didn't have a problem but I can't be sure. Wonder if the timing could be off a couple of degrees and cause something like this ?

 

[Sky65]

I wonder if you are getting some mech advance at idle? Put a timing light on it and raise and lower the idle speed and see if the timimg changes. I don't believe you should have any mech advance below 1000 rpm.

 

[motorman]

I can't seem to make my engine in my '65 ( rebuilt original 350hp ) with an Edelbrock 650cfm carb, idle properly. Sometimes it seems to be o.k., but other times with the idle set around 750-800rpm it will run for around a minute-more or less- and them just die like it's out of gas. If I bump the gas to keep it from dieing, it speeds up just fine, but in a minute it starts to die again. It doesn't happen every time, but more often than not. I try adjusting the screws on the carb and sometimes turning them just barely will help, but next time I drive it, it starts doing it again. The carb only has around 500mi. on it. This problem started after the engine was rebuilt. Lastly, if I set the idle speed to around 1100 or so, I doesn't seem to do it.
Tom

remove the power piston springs,reinstall the power pistons and see if the problem goes away. if it does you need lighter springs in the power pistons as they are pulsating at idle. make sure your distributor weights are not sticking also.