holley carb idle problem

hi folks. i have run into a snag. i just put a new 600 holley carb on the 318 in my 74 roadrunner and i have run into an issue that baffles me. the carb will not idle down to anything less than about 1000 rpm. the motor has an edelbrock sp2p 318 intake on it and i added this brand new out of the box 600 holley to it. the idle screw on the side is completely backed off,the timing is set at 10 degrees initial,and to get it to idle down,i have to have the mixture screws on the metering plate jacked so far in,that the car runs terrible. you can actually grab the throttle arm and physically pull it forward and it will idle down,but it takes more force than the return springs can provide. and i have double springs on it now. there are no vacuum leaks anywhere,and i have checked everything. throttle liinkage has plenty of slack and the detent slide is not binding. even took the carb off,took it back and got another new one. car runs great otherwise. any help would be appreciated.

Wow! That is a tough one...... Usually this would be a linkage issue. If the throttle linkage isn't adjusted right then that causes this problem but if that has been checked then you might have a miss-adjusted throttle arm linkage someplace. Especially if you are able to push down to get it to idle right.

Sorry that's all I have.......

with the carb off the car would the throttle blades close completely?

yes,checked the carb of the car. blades shut just like normal. i have heard the trick of loosening the screws on the plates,slapping the throttle shut a few times and re-installing. but i have not tried that yet.

the carb is good by itself,thats good.are the blades hanging up on the base gasket? if you set it down on the intake it's good? & when you tighten up the mounting bolts it ends up binding?

Do you have some type of heat sheild in place. If so that might be an issue too.

got it fixed. loosened the the blades,adjusted them slightly,which allowed the blades and shafts to close all the way. now i have idle screw adjustment,and car idles smooth as a mothers love. thanks for the input.

thats good to hear

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got it fixed. loosened the the blades,adjusted them slightly,which allowed the blades and shafts to close all the way. now i have idle screw adjustment,and car idles smooth as a mothers love. thanks for the input.

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As I was reading your post and the first few comments, my first impression was that the butterflies were not closing all the way. I've had the same prob with cheap gaskets on a six pack.