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Discussion Starter #1
I have a fairly stock 68 camaro 327 with a 4bbl rochester. The 4bbl was rebuilt about 1000 miles ago. Within the last month the car has been difficult to start cold, once it does start it runs and idles fine no hesitation etc.. Warm starts are fine also. The problem that has been plauging me is most times when starting cold I will pump the accelerator twice to set the choke which appears to work alright fast idle cam sets up etc.. other times the car will stumble and just barely be running then other times the engine will start and race to a dangerously high RPM. I shut the engine off immediately. Then on a restart it fires right up and runs normal??? This event is what is troubling me? It almost seems like a temporary vacuum leak. It also is harder to start the longer it sits This is a daily driver. I checked the accelerator pump when cold a few shots then the gas would just dribble out. I wasnt sure if the bowl was leaking down. Thanks for any advice :confused:
 

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all righty then. it's been a looong time since i messed with carbs. but here goes. i'm sure somebody with more current carb experiance will chime in later, but for now...

1) only pump the pedal once to set the choke. and then just a light to medium tap is all thats needed to set the choke. you may be flooding the motor, hence the bogging or wild rpms. is the double pump a habit you had before the rebuild? try starting it without touching the pedal.

2)rebuilt 1 month ago vs. starting having these problems about 1000 miles ago. seems to me these might be related.

3) the accelerator pump will pump out all the gas in it's chamber/well in one or two strokes with the motor off. this is normal.

4) check your choke, throttle blades and linkages for any kind of binding. are the throttle blades centered in the bores, or are they hitting off to the sides. if you back the idle screw off they should close dead center with no gaps anywhere.

did you remove the throttle blades from the shaft?? if so you may have put them on upside down. the edges are beveled to only fit one way.

it's possible you have a linkage not installed correctly, or the throttle blades are hanging up

have you changed air cleaners? check for any binding between the linkage and the air cleaner. try starting with and without the air cleaner.

that's about all i can think of for now. check this stuff and maybe by then one of the carb experts will chime in with some more things to check.
 

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Discussion Starter #3
Thanks for the feedback and all the suggestions. The carb rebuild falls within the 90 day period so I am going to return to the local rebuilder to have him check out as I am no expert on the 4mv 4bbl
 
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