cmg1

1973 stock 350 w/ rochester, carb has been remanufactured and swaped out twice, problem is idle set at 900 when in park, however, when put into drive, idle drops to 600 and engine misfires and sometimes will stall. have tried increasing idle but too fast knocks car into geear with a bang (automatic). also, when car is started, idele leaps to 25 and takes 5 or so minutes before it comes down , is this normal?

any ideas what the problem is? dwell is set at 30, i have not set timing, would this cause problem??

i did not have this problenm with old carb.

any help appreciated.

john73bb

Kind of sounds like your idle mixture is not correct. There are two idle mixture screws that you can adjust. Hook up a tachometer and then for each one of them, adjust it out till you get maximum RPM, and then turn it in till the RPM just starts to drop. If RPM goes up much above the spec RPM, adjust the idle RPM back down. You may want to go back and forth between the two mixture screws a couple three times till it is just right.

Wendell Allen

I'm assuming your limiter caps have been previously removed from your carb since it's a rebuilt. And in case you haven't already done so, I'm going to give you the instructions from the factory service manual on how to set the idle. I followed these (after much frustration trying to do my own thing), and haven't had a problem since.

And just to make sure, If I were you I'd disconnect every accessory vacuum connection you have to the carb while you're doing this. Even slight leaks in the headlights or air box will throw things off.

1) Tune up the ignition to factory specs. Make sure the dwell, timing, and idle (as best you can get it) are right. All are set with the vacuum advance disconnected.
2) With the vacuum still disconnected, back out each of the idle screws 4 full turns from the seated position.
3) Adjust idle stop solenoid or carb idle speed screw to obtain "initial idle speed". That speed is different for different motors, but is around the 630-650 mark for cars with auto trannies.
4) Adjust the mixture screws equally in (leaner) to obtain final curb idle speed. For my car, this was 600.

Of course as soon as you hook up the vacuum advance after this proceedure, the idle will go up again. So although the factory manual didn't say to readjust the idle after I reconnected the vacuum advance, I did so. But I didn't do it with the two Idle mixture screws. Instead, after I hooked up the advance, and with the car in neutral, I simply backed out the idle screw on the throttle shaft until I reached my magic 600 RPM.

You might give it a try. I haven't had a problem since I did this. But keep in mind that if you have any leaks in the accessory vacuum system, you'll continue to have problems until you fix them.

nunus79

[QUOTE]any ideas what the problem is? dwell is set at 30, i have not set timing, would this cause problem??QUOTE]

Try setting the timing before touching the carb. The timing will affect engine vacuum. Engine vacuum will affect the carb. Might just be that your timing is a little retarded right now. That would cause the problems you're experiencing.

Larry B.

I have never had any success with remanufactured carbs! EVER! A new Q jet from Edelbrock will solve the problem, of course I am assuming you have checked all of the other posible causes such as vacuum leaks, sticking advancem weights, proper dwell etc,etc. :reddevil