74 tbird super high idle.

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Brettstgermain74
Posts: 3
Joined: Fri Nov 25, 2016 1:32 pm

74 tbird super high idle.

Post by Brettstgermain74 »

Just bought a 74 big bird with a 460. Ran ok taking it off the truck.. But had no coolant, 2 carbon coated plugs, bare plug wires. A stuck thermostat, replaced plugs, wires, cap and rotor, radiator and cap, and fan clutch. And oil change.. Now it idles so high i shut her down. Lookin at the engine it has a new holley 600 cfm on it. It starts and idles but runs hot and well above 2000 rpm and snapping the throttle makes the rpms go even higher.. Im not carb savvy but i think the holley is a square bore and the orig motocraft carb thats in the trunk is a spread bore. All Hard to tell but the intake looks like the back 2 poets r a larger but not by much.. This spankin new holley has the idle screw backed all the way out not even touching the linkage. Im not understanding how this carb is even working on this car. The car idles so high n wants to drive itself. Just releasing the brake pedal the car launches with no gas pedal required.. Is this carb wrong for this engine., i found a spacer under this carb.. Has the orig gasket between spacer n intake its old but isnt torn and on correctly..and between carb and spacer it was double gasketed.. Both gaskets not perfect.. One was missing the ear where the mounting stud goes through and the other had a small rip in the back 2 ports in the gasket and backwards. This issue is beyond my abilities.. Verry frustrating. Any help.. Ideas. Suggestions. Or shouldbinjust send this bird to the crusher. Please help.
tbirdman77
Posts: 10
Joined: Fri Dec 11, 2015 9:41 pm
Location: Atlanta area

Re: 74 tbird super high idle.

Post by tbirdman77 »

The only reason for hi revs is too much gas. I suspect the carb is faulty. Call "Guaranteed Carburetor" in Florida for the correct carb for your 460.
PS if the secondary ports in the manifold are larger than the primary than it had a "spreadbore" carb originally.
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