460 woth holley carb.. Idle too high

[brettstgermain]

I have a 74 thunderbird with a 460. Has a idling issue.. I just bought this car, it has 120k miles. Has a shiny and new 600cfm holley carb on it and the trans linkage extended. Idled great the day i got it home.. Went for a ride and it overheated and boiled over.. Replaced the radiator, thermostat and new coolant. Water pump seemed to be working. Gave it an oil change, new plugs..(2 were carbon coated). Still idled great.. The next day it was acting like it wanted to drive itself..constantly picking up speed on its own. So i installed a tach.. Oil and temp guage to see what its doing..oil pressure is around 70 and temp runs around 200 till i shut it off. Gets hotter after i shut down.. Installed temp guage in the thermostat housing.. It smells hot. Tach says 1800 at idle warmed up.. If i touch the gas it revvs higher on its own and hangs there.. Engine gets hot and i shut her down. I wanna scream and take a hammer to this holley carb. I curse the old man that sold me this car. I did a compression test and my lowest was 142.5psi and the highest was 152.5psi. i assume its good. My brain is fried from searching the net for answers. The carbs idle screw is allll the way out and not touching the linkage. And the elec choke is set center for rich/lean. I checked for a vacuum leak and cant find one. I tried to retard the timing.. But only backfires.. This thing idles wayyyy to high. Please help.

[brettstgermain]

Also replaced the cap and even the fan clutch.

[brettstgermain]

Rotor too. Cant get it to idle down.

[brettstgermain]

Pulled the carb off and found a spacer.. It has a port in the and has a home crafted block off plate on it. The bottom gasket was old but wasnt ripped.. The top side of the adapter had 2 gaskets.. One with an ear missing and the other with a tear in it. And was also backwards.. It even says front on it.. The dude that installed it needs a beating.

[brettstgermain]

Anyone have any thoughts or ideas before i take a hammer to this car n sell it..

[brettstgermain]

Ripped this pos holley off the engine, looking at the bottom of the carb i found all 4 venturi to be the same size.. And the intake has 2 larger and 2 smaller ports.. Theres a spacer with a home job blocking plate on the rear.. The intake to spacer had a square bore gasket and the spacer to carb had a double gaskets.. Both Spreadbore... And backwards..One missing an ear(where the mointing stud is) and another on top of it has a tear in the secondary side. The intake i assume is a spread bore.. 2 big and 2 small ports. I am reading on here that a spacer will allow it to run.. But square bore and spread bore together are a no go.. Could all this be my high idle issues..? Opinions.. Input..?

[65comet]

I have never had any luck trying to put a carb on an engine that it wasn't built for by using an adapter spacer. Smaller holes to bigger holes, vice versa or mixed as in your case. Either it wouldn't idle at all or constantly revved higher and higher. Best to get a carb that matches the motor and manifold. Without proper flow, you just can't get proper control of the air/fuel mixture.