Adjusting Idle

[celeryman22]

Hello, I got the timing on the vette set pretty good I think. But right now the car idles really high. I just got done rebuilding the motor and the carb was just rebuilt by the local carb guy. I read that I should connect a gauge to the vacuum line and set the idle to achieve max vacuum. Right now I have no dash on the car so I cant tell by the RPM's what its reving at. By the sounds it seems to be around 1500 or so. I dialed both idle mixture screws in and dialed them back 4 turns. Should I start to dial them in to lower the speed? What vacuum port do I connect to.

Any help would be great.

Thanks
Mike

 

[red70vette]

Don't trust your ears. Wait until you have a tach to set the idle speed. How did you set the timing without knowing the speed of the engine?

A tach is critical in tuning up the car. Do that first.

 

[RodsnRides]

Agreed-you need a tach. You can get a cheapie tach/dwell meter at Checker or Pep Boys, that should be sufficient. There should be a direct vacuum outlet on the choke side (passenger side) of the carb-comes straight out about 1 1/2".

The idle speed screw will be at the throttle shaft, regular screwdriver, approach from carb front. You'll see it has a little spring, too. Bring your speed down to about 850-900 if an auto. Recheck your timing (distributor vacuum disconnected), adjust if necessary, recheck idle speed, THEN start playing with the mixture screws, adjusting idle speed as necessary. Put car in drive and determine if that's the stoplight idle speed you want-especially with A/C on, if applicable. Cycle a couple times, blip throttle, to ensure it "settles" where you like it.

Optional: balance can of beer on air cleaner to confirm smooth idle. Impress your friends.

Rick

 

[waterboy1976]

Optional: balance can of beer on air cleaner to confirm smooth idle. Impress your friends.

Rick

By the time I ever get my idle that smooth....the can of beer is EMPTY!!!!!

 

[celeryman22]

I set the timming "by ear" and using the timing light. I noticed the little screw and the spring on the drivers side. Currently it is dialed all out then I turned it in until it just touched the rod. Turning it more pushes the accelerator pump down.
Currently the timing is set to where the engine will stay running on its own. How can you set the correct timing if the engine will not idle? Is this one of those cases of which came first "the chicken or the egg".

Thanks
Mike

 

[Vettehead Mikey]

You don't set idle speed by playing with the idle mixture, you set it with the throttle stop only (or hex head on the idle solenoid if your car has one.

Don't know who taught you to do a tune up the way you've described, but it's no surprise you're having problems

 

[celeryman22]

I got it, well not me the local dragster guy, who I bought my house from. Turned out I needed to plug the ports in the front of the carb. Once we plugged the ports on the front it fired up and idled almost perfect. He also turned up the idle screw. I was under the impression you need to use the idle mixture screws to set the idle, but now I understand whats going on.

Thanks guys for the help.

 

[wishuwerehere82]

Idle speed is set with the screw on the throttle stop. Idle mixture is set with the two mixture screws on the front of the carb.

1) set your idle to around 650-700 RPM.
2) set timing with the Vac. advance disconnected and plugged.
3) reconnect Vac advance.
4)Hook up vac. gauge and adjust mixture screws to max vacuum at idle. Set initially at 1-1/2 turns out from full closed position.(Usually 1-1/2 - 2 turns from full closed position.)Adjust each needle valve one at a time and then slowly open and close from the max Vacuum position to verify that it is the max Vacuum.
5) Reset Idle speed to 650 RPM with thransmission in drive.