it might only run well at 1000 rpm or might be fine at 750 , it depends on your engine and if its stock or has been modified at all ( even different jets in the carb will make a difference )
625 if it has a/c running
make sure the rest of the driveability has been adressed.
make sure your timing is actually set at the right degrees.
be sure your plugs are the correct kind, number and gap.
set the idle last and save gas. that thing can be a pig and a half if you dont. we compared timing lights at a dealership tune-up line the snap on was used last because the customers issues were then fixed. the other guys were told to take their timing lights home because they were out of calibration. use a vacuum gauge and compression tester, get the settings right
625rpm sounds a little high but it must be right.
Stock engine, auto trans. in gear, 625 RPM about right, around 700-750 in neutral.
Finally I have my 1972 thunderbird running and driving and I've started adjusting everything to run correctly on the car. I've been trying to figure out how low the idle speed should be. On the side of the valve cover has a sticker that is supposed to say the idle speed but it's slightly ripped so I don't have the full sticker. The only numbers I can read on it is 625 rpm which to me sounds really low for a 460 big block V8. What speed should I bring the idle to? It's idling currently at 850 rpm.
