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Discussion Starter #1
I'm having an awful time with a lean issue, I'll try to add all the things I've done cause I need serious help! Setup is 347 with turbonetics 67 mm turbo, blow through carb, boost ref reg, boost reference msd, makes 12 psi, a1000 pump, all an lines w/return, timing is 28 deg total, plug gap is .022, I'm sure it's not all listed but feel free to ask.
So, I can take the car out and drive it and it's decent, was in the middle of tuning. Wideband is 12.5 at cruise and 13.3 under boost, it was hitting good 2-3 gears. Came back and made jet change, that's how I made the 13.3. Then I went down and now I mat it and it holds 13.3 for about 2-3 seconds and then it spikes the wideband and lean pops. Since this I added the a1000 pump, it's making fuel psi so I'm now stuck, I don't even know where to go from here...
 

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You are going to melt that motor down if you keep going into boost.
Your fuel pressure should be rising 1psi per lb of boost.
Your a/f is way lean under boost. At 10psi I would shoot for low 11s a/f.
You're also not running enough timing. You are going to damage the exhaust valves pulling 2 degrees at 10psi boost.
You have to figure out why you came low fuel pressure.
I wouldn't get into boost till you figure it out.
 

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Discussion Starter #4
Fuel psi is 1:1, it has around 15 ish psi under boost, and I have huge jets in carb 99 sec 84 pri. Is there a trick to fatten it up?
 

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Well, carb was "converted" to blow thru, but it did come off a boosted sbc
Did the SBC melt his motor, then sold carb to you? I would never trust a used blow through carb without going through it yourself to make sure all the proper modifications have been done.

And I agree that total timing is too low, since you are pulling a good bit of timing out under boost as well.
 

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You might have pressure before the carb but maybe the fuel isn't getting into the bowls? Don't they make a higher flowing needle and seat?
 

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Mine had a lean spike when it started to come into boost. I was at 34deg bumped it up to 36-37 and it was happy. I started off pulling 2deg per lb. Im at 1.5 per lb now.
 

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4psi fuel pressure seems low. Jets are pretty large for a pump gas setup, probably ballpark for an E85 carb. I'd be looking into an issue somewhere in the carb. Check the rear jet extensions for obstructions with the float, (make sure its not holding it up) also 2° per psi of boost is pulling way too much. When you get the fuel more dialed in I'd try for a 1:1 or .75° per psi if on E85.
 
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