[kenneth77]

my father has a 1957 olds super 88. engine is the original rocket engine with hydramatic trans. it has a very rough idle. if i put my hand over the carb when idling,the idle sound okay,as soon as i take away my hand,it idles low and rough again. what would you suggest i should look at? the idle mixture circuit,screws?
if i raise the rpm when it idles,the engine sounds ok.
the choke on the carb has been disconnected.

[Lightfoot]

Kenneth Quote: "It has a very rough idle. if i put my hand over the carb when idling,the idle sounds okay, as soon as i take away my hand, it idles low and rough again."

Does it do this when the engine is completely warmed up? If yes, then I would say the idle mixture is too lean. Or it is also possible that there are one or more vacuum leaks that are causing the bad idle.
If it will stay running, try spraying some arosol carburetor cleaner around the base of the carb, near the vacuum hoses and where the intake gaskets are. Pay attention to see if the idle picks up, when you spray each spot. That will point you to a vacuum leak. A dry rotted carb base gasket is one of the typical places that would develop a vacuum leak.

If it acts that way when cold, then it could be because the choke is not on there to help it idle until the engine warms up.

Also you should copy this question to the '61 and older Pontiac TECH section.
I'm sure someone will be glad to help.