I have 66 longwide C10 pickup with 235 six cylinder one barrel carb that starts out with a normal idle then the longer you drive it the idle seems to go up. after you arrive at your destination the idle is very high! I could use some help here. thanks.........

Possible cause-linkage sticking....when it is at the high idle open the hood as pull back the lever on the carburetor....does it then slow down?I assume that it has a hand choke.

Also a 1966 will not have a 235 engine.Will be either a 250 or 292....or is it a 1956?

Duh! It is a 250 I don't know where I came up with 235. Yes it has a hand choke. and I will try the throttle linkage. thanks for the help.