Carburetor, Lean Mixture Screw help needed
pcmaher
11-01-2004, 07:23 AM
1987 Olds Custom Cruiser with 307 and a Rochester 4 barrel. I rebuilt the carb recently. Car does not stall anymore, but idle is not as smooth as before. I feel it may be because the Lean Mixture adjustment screw is not set properly. Like a goofball, I did not count the number of turns it took to pull it out of the carb, so I had no reference point to re-install. Can someone share with me how to set this properly?
auto trainy
11-05-2004, 07:16 PM
Its just a thought but check for a broken vacuum line
(small hoses),the power valves are 3/12turns out but you'll need a tool.
(small hoses),the power valves are 3/12turns out but you'll need a tool.
pcmaher
11-06-2004, 05:58 PM
I made a tool from a small flat blade screwdriver. Fits perfectly. Is that 3 an 1/2 turns out from fully seated? Thanks for the response.
auto trainy
11-07-2004, 06:07 AM
Don't forget I said power valves ,which are located onder little plugs(they are like little freze plugs).as far as idle screw adjustments I didn't know they allowed them,but the way I used to adjust them was to turn them in untill the engine started to stumble and back off untill smooth,it really should be done with an exaust anilyzer for pollution,good luck.
pcmaher
11-08-2004, 07:57 AM
I think we're talking about the same thing auto trainy. The exploded diagram I have calls this component the Lean Mixture screw. I'm not able attach the image to show you. Can I ask you to take a look at this website?
http://dyeager535.topcities.com/CCCqjetdiagram.html
Look for item #226. This is the screw I'm talking about. It is underneath one of those little brass plugs as you mentioned. Should this screw be fully seated, and then backed out 3 and 1/2 turns?
http://dyeager535.topcities.com/CCCqjetdiagram.html
Look for item #226. This is the screw I'm talking about. It is underneath one of those little brass plugs as you mentioned. Should this screw be fully seated, and then backed out 3 and 1/2 turns?
auto trainy
11-09-2004, 05:18 PM
Ilooked at the drawing and it would be fully seated and then backed out 3 1/2 turns out.Your figures 422 & 425 are your idle mixture screws and caps,make sure to adjust them as well.I still stress looking for a slight vacum leak,try cupping you hands over the carb while idling and see if the enjine smooths out,if it does your running lean,GL.
Automotive Network, Inc., Copyright ©2026
