My friend has a 4160 carb that has never run right. He just went through it and didn't find anything wrong. After getting the carb installed, we were able to get the choke to actually work, played around with the choke pull off, and the fast idle speed. Set the floats. Then after the engine warmed up we started working on the idle speed and mixture screws. They were 2 and a half turns out when we installed the carb, half turn at a time we kept threading them in and the vacuum signal kept improving, and the idle speed increasing. Finally we got to the point of having both screws threaded in all the way and the engine kept idling. I checked and it isn't getting fuel out of the venturies. What could be the problem? Power valve leaking? other internal leaks? Where are the potential internal leaks? Crack in the body somewhere?

turn down the curb idle speed, thats the screw that moves the throttle up and down. You may have the butterfly's open so far that your throttle blades are past the idle ports and your getting fuel from the transition slots.
I would turn out the idle screws back out 1.5 turns, turn the curb idle down to around 600 rpm then see if the idle mixture screws start working. jim

Exactly which carb is it? 4160 isn't helpful. Look on the front of the choke housing inside the air filter area, should have something like this, LIST-1850, with possibly -1, -2, -3, etc.

Now, some Holley's are emissions calibrated replacement carbs, and work with dead stock engines ONLY, even a K&N air filter element messes them up. Those emissions carbs also use a reverse idle system, fixed jet size, always too lean, and, will run better when the air screws are turned all the way in.

Post the LIST number, and we can go from there with it.

Regards,

Milton

The Holley video says if you can crank the idle mix screws all the way in that you have a bad power valve.

As Jim Mac says, crank the idle speed down as you adjust the mix screws.

More important, what are the engine details?
Do you have a performance cam?
What is the base and total timing?
Have you checked everywhere for vacuum leaks?
What is your current vacuum at idle?

Probably best to
set the idle mix screws 1 1/2 turns out then
start the engine
set the initial timing to 16-18 degrees
THEN set the idle speed to 600 or about as low as possible
recheck the timing
then set the idle mix for highest vacuum (use a gauge)
adjust the idle speed down if it comes up during your adjustments

kettbo is right. Put a new power valve in the carb and you should be able to dial it in correctly.

Sorry I should have reported back in last night. About 15 minutes after I made the post he tore it back down and found that he left the gasket off the power valve.

I don't have the carb number infront of me but if we have another question I'll make sure to post all that information with it. I know its not the style that has the reverse idle screws.

Thanks for all the help guys.
Scott

>> "....he left the gasket off the power valve."

That'll do it alright. Easy cheap fix for once.