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Old 11-09-2006, 10:57 PM
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BG/BC Rich Idle & Idle Air Bleeds/IFR

My 383, 8-71, 2 BG 750 (no idle-eze) BC's idles VERY rich at 3/4 turns out on all corners, idle is fair at 1/2 turn out but still rich. Throttle plates are square in the bore and transfer slot is looking good.

When at the recent Vegas Delco Nationals I spoke to the BG folks quite a bit -they recommended opening all four idle mix screws 1.5 turns and incrementally open up the idle air bleeds (.070 out of the box) until idle passes acceptable and gets funky, then back down one or two 1/1000. I bought a bag of bleeds. He never mentioned the IFR's, which are .036 as delivered.

The Ray Bohacz BG guide recommends initially decreasing the IFR since opening the air bleeds by themselves will change the fuel curve, and could cause an off idle lean condition or stumble. The throttle response as it is, is instantaneous, nice...but rich idle will bring tears to your eyes, not to mention foul plugs. Fuel pressure is at 9# idle, timing initial 18 deg and floats are set in the middle and using the original pink pump cam, Lunati solid roller, .540, 224/232 @ .050, 112/108, 1.6 rockers.

So - how much can I open up the air bleeds before I cause additional problems without having to get after with the IFR's? A guess at the optimum size?

Thanks, Larry

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Old 11-10-2006, 03:54 PM
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Every application is too specific to guess accurately.


I wouldn't use bleeds to tune idle air ratio's. I'd use a good carb specialist.
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Old 11-10-2006, 04:21 PM
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Does BG want you running the fuel pressure at 9PSI. That is the first thing I would verify to make sure that's not part of your problem.
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Old 11-10-2006, 11:36 PM
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My dicussions with the rep at the track over the four day event were pretty in depth. Yes he was good with the fuel pressure, jetting and carb selection for my setup. He was also straight forward and adament on the air bleed adjustments.

My question is whether I should give more attention to the IFR's before I address the idle air bleeds.

jon - I'm with you on using a good carb shop for major surgery, but they're aren't any reliable specialty shops here in Alaska that I'm aware of. The changes/adjustments I'm making are simple and reversable, no brain surgery involved and BG's tech publication is a comprehensive easy to follow guide.

Looking for BGTech to jump on this thread as well.

Thanks, Larry
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