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i was wondering if u could help us. we have a 1979 Mustang with a 1969 Boss 302 motor in it. the motor has a offenhauser tunnel ram with dual holley 600 cfm carburetors. we have some questions and didn't know if u could answer them. we got the thing to idle at about 1000 rpms where we wanted it to. then it started to bog down every time the electric fans turned on. it quit doing that but now once we get it to idle where we want it and it stays there when it is warm the next day when ever we warm the motor up it won't idle the same it always dies. we didn't know if u had any idea wat could be causing all this to happen.
 

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Keeping 2 big carbs and that huge intake properly fed and happy is complex at best. It's a racing setup, not a daily driver setup. If I had to guess (which of course is what I am doing) you have too much carburetion for the needs of the motor underneath.

You are probably vacuum starved as well. Does the car have power brakes, for instance? If you block off the vacuum lines to any accessories, does it idle normally?

What has been done with the heads (etc) that flows enough to utilize all that fuel/air mixture?
 

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How about cam or the bottom end?

Sometimes people go overboard with the top end, and 1200 cfm for that motor is twice what it normally needs. To support that much air/fuel, the engine should be running a big cam and upgraded heads, and maybe a stroker bottom end increasing the displacement.

Otherwise, you are trying to stuff 10 pounds into a 5 pound bag.

PS: I would recommend 1.75" headers with that combo, too.
 

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I'm with 3 Black. The Boss 302 used what were essentially Cleveland heads. Cleveland heads flow but probably not that good. If you have a true Boss 302 it might be worth looking into selling the motor to a resto guy and putting in a more streetable roller motor.
 
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