carb question

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Mar 9, 2013 | 09:40 PM

85bronco85

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carb question

hay fellas. i decided to change the old motorcraft carb out for a new holly 350. put the carb on did very little adjusting cause it idled beautyfull and drove it around stoped here and their fired up and ran nice every time. on the way home the passenger side exaust fell off the header russted out
pulled over still ran fine took the exaust all the way off and throught it in the back sat at astop light of about 10 min idleing still good. turnd and almost all the way home it stalled out at the stop light and wont idle right could the exaust missing be an issue with the idle
hope some one has some real good advise

Mar 9, 2013 | 11:25 PM

GruesomeJeans

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From: Algona, Washington

For starters I assume it's an 85 bronco with the 302 motor? Anyways, I would check thw vacuum lines first, they can be troublesome at times. The Exhaust missing could cause a bit of an issue but it should cause it to stall out. My 78 has a bad leak and doesn't seem to idle right. Do you know what the curb idle RPMs are? Also make sure the lean/rich air/fuel mixtures are good.

Did it sputter and die or just completely die all of a sudden?

Mar 10, 2013 | 09:07 AM

85bronco85

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it was idleing nicely at 1000 to 900 be for the exaust fell off and when it died it thwn idled at 500 to 400 i truned the air fuel screws up a 1/4 turn to rais the idle. i had to turn them down when i fist had the carb on and warmed up cause it idle at like 1500 warm . ill check the vacum lines and get back to u

Mar 10, 2013 | 02:03 PM

85bronco85

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just fell as i stoped i couldnt hit the break and the gas at the same time

Mar 10, 2013 | 04:07 PM

GruesomeJeans

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From: Algona, Washington

You should also have an idle screw on the throttle piece. It should press against the carb body somewhere and force the throttle out a little with each turn. I don't know about yours though.

Mar 10, 2013 | 04:50 PM

85bronco85

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i did that but know it walls on its face when u start driving like its getting to much gas
or not enought

Mar 10, 2013 | 05:29 PM

greystreak92

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From: Gateway to the West

And you all wonder why I prefer EFI and fault codes. But I digress.

I would second the idea of checking vacuum lines and anything else that might have gotten smacked or damaged when the exhaust fell. Running open as opposed to full exhaust will have some affect on things but it shouldn't be that extreme.

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Mar 10, 2013 | 06:35 PM

GruesomeJeans

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From: Algona, Washington

Quote:

Originally Posted by greystreak92

And you all wonder why I prefer EFI and fault codes. But I digress.

I would second the idea of checking vacuum lines and anything else that might have gotten smacked or damaged when the exhaust fell. Running open as opposed to full exhaust will have some affect on things but it shouldn't be that extreme.

Psh you and your fancy newfangled EFI systems

If it's falling on it's face then it might be getting too much, try leaning out the screws and see what happens. I believe most carbs have a 1.5 to 2 turn spec on those air/fuel screws. Like, you screw them in all the way then back them out 1.5 turns or 2 turns depending on what works best. It's a good starting point at least. Re-check timing, and take some carb cleaner and spray around the base of the carb/intake and see if it is leaking or not. Also a trick I learned for checking for vacuum leaks is to choke out the carb either with your hands or whatever. If the idle kicks way up, you got a leak somewhere. If it starts to die, you should be good.