11-1 383 atk/profiler 210 carb tuning questions. - Chevelle Tech
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post #1 of 22 (permalink) Old Oct 18th, 19, 4:03 PM Thread Starter
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Shane
 
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11-1 383 atk/profiler 210 carb tuning questions.

Engine is 11-1, [email protected] solid flat, atk210 heads, 300-25 intake , 750 Brawler carb , 1 3/4 header 3inch dumped, full msd ignition . Fr5 Ngk plug.

I live in Billings Montana , 3,300 ft.

I have a 67 jet and 3.5 PV (think I need 2.5) and am running a 10.0-10.5 AF in cruise . I feel like I’m not going to be able to lean it out enough . Change high speed bleeds ?? I have jets going down to 64 but seems small. And gauge is right it’s rich, I changed from the 72’s to 67’s and it runs much cleaner .

This combo is a beast by the way . Feels great ! Coan th350 fmvb, jegs xhd 3500-400 stall. 3.73’s holding it back but makes so much torque even in 3rd cruising doesn’t matter . For racing would love more tho . I’ll post a video , this is just from break in and tuning , wiring/fuel line still crazy and not buttoned up, don’t judge lol.
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post #2 of 22 (permalink) Old Oct 18th, 19, 4:11 PM Thread Starter
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Shane
 
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Belt squeeked lol also is pushing a little oil out breather . Prob do different valve covers and catch can or something . Makes ~70-80 cruising . https://youtu.be/FVvXcV7kdZM

https://youtu.be/foVTSRKMCks
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post #3 of 22 (permalink) Old Oct 18th, 19, 5:11 PM
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Re: 11-1 383 atk/profiler 210 carb tuning questions.

Dig SFT cams lets see some action clips

Is that small of a pv normal for that altitude, curious

Seems awful small.

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post #4 of 22 (permalink) Old Oct 18th, 19, 5:38 PM
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Re: 11-1 383 atk/profiler 210 carb tuning questions.

You're nowhere near the power valve at cruise. Your problem isn't in the main or power valve. It's in the idle and transition circuit. You cruise on the transition circuit which is fed by the idle feed restrictor. The power valve feeds the main circuit and therefor cannot affect the transition/idle. What is your cruise vacuum? Find out what that is and take a couple numbers off and that's what power valve you should have. As in if your cruise vacuum is 10.5 at 1,800 RPM I would run an 8.5 power valve. You're probably closer to 20 at cruise though so I recommend a 10.5 power valve as that's the highest opening you can get. You can lean the cruise by leaning out your idle mix but it won't get you where you want to be. I can help you get there but first tell us about your ignition setup. Let's get that sorted and then we can make your carb work.

One thing I'll tell you right now is forget about having a perfect AFR in all situations with a carb. You'll go insane trying to achieve it and it's only part of the story anyhow. You need a five gas analyzer to get it perfect and it's just not feasible. A wide-band is a great tool but it's just a part of tuning. You can't live and die by that one tool alone. You can set a carb to a rich AFR on the WB and pull a plug and it will tell you it's lean.

BTW I'm at 5,000' so I know a little about tuning at altitude.
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post #5 of 22 (permalink) Old Oct 18th, 19, 6:40 PM
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Re: 11-1 383 atk/profiler 210 carb tuning questions.

Tommy is that due to the gas? (02 says rich and plug appearing lean)
Having issues getting mine right also. Powerful but nowhere near what it ought to be.

Gave up trying to read plugs

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post #6 of 22 (permalink) Old Oct 18th, 19, 7:23 PM
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Kerry
 
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Re: 11-1 383 atk/profiler 210 carb tuning questions.

The Brawler carbs suffer from the same issues as the Quick Fuel carbs, oversized transition slots, too much emulsion, and IFR located high in the metering blocks instead of low.
Moving the IFR to the low position in the blocks, reducing the emulsion, and installing .081" transfer slot restrictors in the main body for primary and secondary should be the first thing you do.
Which model 750 Brawler do you have?
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post #7 of 22 (permalink) Old Oct 18th, 19, 7:44 PM
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Tom
 
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Re: 11-1 383 atk/profiler 210 carb tuning questions.

There's a lot of factors and I honestly don't understand them all. I've never spent any time with a 5 gas and you don't need to. You just have to use all the tools you do have. Your plugs and MPH won't lie to you. A WB can get a diluted mixture due to cam overlap, leaking headers, etc. Also a misfire will show lean on the WB because the oxygen wasn't burned. A WB doesn't read how much fuel is in the exhaust, after all. I use the WB all the time and it's taught me so much but experience tells me that you also need to use all your tools to get a complete picture of what's going on.

Some other essential tools are-

Sight- look at the plugs. They won't lie but they don't always tell the whole story.

Hearing- WB says it's good but does it sound happy? Lots of old timers could get really darn close based on sound alone.

Feel- does it shake, hesitate, blubber, surge? What does the WB say when it feels good/bad? Most of us are only sampling one bank and the WB gets an "average" of the one bank.

Vacuum gauge and tach- you have to know at what RPM and what vacuum conditions it's acting up.

None of the tools above are 100% effective on their own but when you combine them all you can make great things happen.

But first, and I can't stress this enough,- GET YOUR IGNITION RIGHT! And then leave it alone!

Make one change at a time and write the results down!

Trust mother Holley for your baseline. Put the carb to stock to start; Holleys are typically pretty close if you picked the right one. If anything they'll be off on the safe side.

Get the idle and transition circuits sorted first. They provide fuel at all times except in some circumstances they can act as an emulsion bleed at WOT but that's a non-issue here. Changing the idle and transition has a big effect on the rest of the fuel curve. Get it right first.

A lot of times I'll disable the secondaries until I get the primaries right. I've also blocked PVs to take that variable out of the equation.

Be patient. You'll learn more every day if you stick with it. I expected to be a carb master as soon as I got a WB and I was very disappointed. It takes time. I'll let you know when I get there so stay tuned. I hope you have another 50 years to wait....

70 Camino...Roller

69 Malibu Stock 307, Reverse Manual TH350, 4,500 Stall Edge Converter, 4.56 Spool 35 Spline 12 Bolt

76 C20 VortecPro 496 628HP 655 lb/ft TH400 Edge Converter, 4.10 14 bolt
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post #8 of 22 (permalink) Old Oct 18th, 19, 8:13 PM Thread Starter
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Shane
 
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Idle is steady and strong at 12.8-13.0 .. when I’m light to half throttle I’m stuck in the 10’s with a 64 jet now !!! It does blubber at low speeds and is rich on the plugs . I’m about 11.1-11.4 full throttle but have not jetted the back yet , wanted to get primary close . Still rich but pulls to 7k no prob , seems strong ! I will post driving clips soon .

I keep thinking I need to go bigger on high speed air bleed or something , jet changes not doing a lot . Have not taken vacuum readings during cruise . It is rich in whole primary side not just transition .

I sized my pv as this does not make much vacuum at idle , and I have had good luck in the past with 3.5 pv in [email protected] + applications . With quick fuel annular carb I had flat AF all the way through the curve with .4 variance.

P.s. I have built quite a few engines and this is my first brawler and first to not get a change with jets .
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post #9 of 22 (permalink) Old Oct 18th, 19, 8:17 PM Thread Starter
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Shane
 
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It does seem happy but could use cleaned up at light throttle and I can tell will make a few more getting trimmed to around 13.0 wot. I would like a 13 cruise as well
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post #10 of 22 (permalink) Old Oct 18th, 19, 8:42 PM
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Tom
 
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Re: 11-1 383 atk/profiler 210 carb tuning questions.

Power valve selection has nothing to do with idle. That isn't how you pick a power valve.

Also, leave the bleeds alone for now.

Re-read what has been posted. Jetting changes won't make much difference until you get the idle and transition right. You're getting too much fuel from them.
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70 Camino...Roller

69 Malibu Stock 307, Reverse Manual TH350, 4,500 Stall Edge Converter, 4.56 Spool 35 Spline 12 Bolt

76 C20 VortecPro 496 628HP 655 lb/ft TH400 Edge Converter, 4.10 14 bolt
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post #11 of 22 (permalink) Old Oct 18th, 19, 8:49 PM
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Tom
 
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Re: 11-1 383 atk/profiler 210 carb tuning questions.

What carb is it specifically? It looks like there's at least 3 different 750s in the brawler line. And I'm afraid Kerry is right, with the way those are calibrated you're in for an uphill battle.

70 Camino...Roller

69 Malibu Stock 307, Reverse Manual TH350, 4,500 Stall Edge Converter, 4.56 Spool 35 Spline 12 Bolt

76 C20 VortecPro 496 628HP 655 lb/ft TH400 Edge Converter, 4.10 14 bolt
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post #12 of 22 (permalink) Old Oct 18th, 19, 10:45 PM
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Re: 11-1 383 atk/profiler 210 carb tuning questions.

Sounds good, but one thing I see is way too much oil pressure when you rev the engine, must be a HV pump. I learned my lesson on those this year. I run a 750 QF and the only thing I have done so far is to get rid of the P/V and I run 80 jet front and 82 rear, so far it's worked pretty good even better than one of my Mighty Demon's. Still have to see if I can get the 850 QF DP straightened out, once I do I think that one will work well also. The Brawler's are good carbs for sure.
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post #13 of 22 (permalink) Old Oct 18th, 19, 10:51 PM
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Quote:
Originally Posted by hereinmissoula View Post
Idle is steady and strong at 12.8-13.0 .. when I’m light to half throttle I’m stuck in the 10’s with a 64 jet now !!! It does blubber at low speeds and is rich on the plugs . I’m about 11.1-11.4 full throttle but have not jetted the back yet , wanted to get primary close . Still rich but pulls to 7k no prob , seems strong ! I will post driving clips soon .


I keep thinking I need to go bigger on high speed air bleed or something , jet changes not doing a lot . Have not taken vacuum readings during cruise . It is rich in whole primary side not just transition .

I sized my pv as this does not make much vacuum at idle , and I have had good luck in the past with 3.5 pv in [email protected] + applications . With quick fuel annular carb I had flat AF all the way through the curve with .4 variance.

P.s. I have built quite a few engines and this is my first brawler and first to not get a change with jets .
Rich at the throttle position you mention is why you need to change the emulsion, and install transfer slot restrictors. Lowering the IFR jet will make the fuel delivery much more consistent at idle and low throttle openings.
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post #14 of 22 (permalink) Old Oct 19th, 19, 10:36 AM
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Re: 11-1 383 atk/profiler 210 carb tuning questions.

what they said already. on the highway at steady state cruise it's very likely your car is running off the idle transition circuit. this fuel comes from the idle circuit and it not adjustable by changing the main jets. Believe it, it's true.

Tom Terrific or Terrible Tom, depending on the phase of the moon, passing cosmic rays or other factors not fully understood except by my wife.
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post #15 of 22 (permalink) Old Oct 20th, 19, 4:46 PM Thread Starter
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Shane
 
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The vehicle is rich EVERYWHERE in primary side , not just cruise ... from off throttle to half throttle vehicle is in high nines to mid tens . Idles very well at high 12 low 13 . Idle adjustment screws are right around turn and half just as they should.

I’m blocking power valve today putting larger jet in see what happens . Try to post driving footage but just have phone and by myself most of time for tuning .

Everything else seems right because it runs very strong .. only have 32 total in it too. Sure it would like more . Will wait till mostly sorted then dyno ....
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