Carb questions.

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Oct 25, 2008 | 08:14 PM

Ford400Man

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From: Gallipolis, Ohio

Carb questions.

I run a 460 motor in my Bronco, mud bogger, and I am not sure if the factory 4 bbl is kicking in or not. Usually you can hear the roar from it but I never noticed it. The motor came from a 74 Mark IV, factory carb, and everything looked hooked up properly. I only unplugged what I needed to and took notes to what they hook into. Is there a way I can check it? I don't think they open unless the motor is under a load,,,, Right?
Don't get me wrong,, The motor runs GREAT!! Plenty of power, just wanting everything to work properly!

Oct 25, 2008 | 09:35 PM

Randoo

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From: Spotsylvania, VA

There are two different kinds of ways the secondaries on a 4 barrel carb open up. Mechanical (linkage operated) and vacuum (manifold pressure). You didn't specify, but it sounds like you have a vacuum operated secondary and missed a hose or one is leaking. This would be the style that works under load of the engine. If yours is a mechanical linkage you should be able to watch it open with the engine off looking into the carb as you work the throttle to full. You could have a linkage problem too. I'm no carb expert, but check these quick fixes first.
Also, are you running an auto trans and its not downshifting? You could be missing a downshift rod or a line to the vacuum modulator. Good Luck.

Oct 26, 2008 | 04:44 AM

Ford400Man

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From: Gallipolis, Ohio

Being unfamiliar with a stock 460, I honestly don't know! But all hoses are hooked up. i replaced them all one at a time when I installed the motor. When I ran the truck, I held it in first gear, I didn't want it to up-shift with 37 inch tires and 3:54 gears. But yes, it is an auto with modulator hooked up and no downshift rod,(460 car rod was not there and the 400 originally from the Bronco is too short.)

Oct 26, 2008 | 10:55 AM

Randoo

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From: Spotsylvania, VA

Well first I would figure out what kind of carb you have (vac vs. mech secondaries) and then you can t-shoot it from there. Go to the Ford dealer and have them look up a carb for that 74 mark IV and they should be able to tell you what kind. Or you could get a tag number off that carb and do a web search on it.
Did you change the cam and put a large high HP cam in? This will not produce a lot of manifold vacuum. If it’s a mech. carb you should see the external linkages first opening the primaries and past half throttle it will open up the secondaries. Take the air cleaner completely off and operate the throttle by hand when you do this.
And remember, hoses that look good on the outside could be collapsing on the inside. GL.

Oct 26, 2008 | 12:52 PM

Ford400Man

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From: Gallipolis, Ohio

Well,, NOW I feel like a dumb ****!
Mechanical secondaries, and I done figured it out! Took about 20 seconds, too!

The choke controls the operation of the sec. plates. the choke LOOKED open, but in fact the lever was only half open. Therefore, not allowing the 4bbl to operate. After I moved the choke fully open and worked the gas, they came open! Now, gonna go run it down the road to make sure!!!

Thanks for helping this retard!!! lol