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Hookedup12 03-15-2013 10:40 PM

Sbf 306 running lean???
I have a 306 and have a 570 street avenger carb on it. I have it at the shop on the dyno and they calle and old me it's running super lean which I truly believe because all the hesitation it was having, not bog just stop then pik back up. But they said I need to step up I have it in a light 68 mustang built c4 Hughes 2400 stall, 3.50 gear, tuned long tubes, custom cam, rpm air gap, forged pistons, 10:1 comp., ported and polished gt-40 heads.

My question is should I go double pumper or vacuum secondary??? I drive it around town no freeway or such just back roads and around town, I want it to still be streetable but I'm not worried about gas mileage. They told me I could go Holley 670 street avenger or 650 dp...

Any opinions???

RWENUTS 03-16-2013 07:56 AM

How,s it run besides the stumble?
What's your timing set at?

Irelands child 03-16-2013 11:30 AM

I'm assuming the carb is new
It's a very good size for a .030 SB Ford. It IS a vacuum secondary carb. It is an emissions carb (kinda). It is NOT anything more then close to being street ready in that you may have to make jet, discharge nozzles or even power valve changes to make it 'right' for your engine/camshaft(whatever a 'custom' camshaft is). Then of course is the timing, curve and initial, and is it set correctly which can show the same effects of a lean condition, i.e. blued and possibly glowing headers.

It's dam' poor dyno shop that can't diagnose and make these changes. I would run, not walk to that shop, pay them and leave - forever - and at the next shop, I would sit and watch

Hookedup12 03-16-2013 04:36 PM

They can fix it. They are extremely good with what they do to old mustangs I've seen over 12 of the mustangs they've worked on at some of the car shows in nc, they specialize in older mustangs. They just gave me the option to try and fix what I have or go for a carb larger over the whole map not just jet and power valve that's all. They are going to Tune this carb as is. And if I want to move up ill try it with a 670 or 650 an record hp number changes. If it is worse ill drop back to 570 but if they make this one work there ain't no need to fix what ain't broke. "Custom" means it was specifically ground hydraulic flat tappet for my combo, I don't have the cam card in front of me so I can't remember right off. Other than the flat spot it runs like a raped ape.

Hookedup12 03-16-2013 04:37 PM

Also it has 6al-2 box, msd pro billet dist. And blaster 2 coil.

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