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Post Info TOPIC: BBC tuning


- GearHead -

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BBC tuning
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If anyone has experience tuning a bbc, I could use a little help.  The engine is idling good, runs good below 3k rpm, but when I stomp on it, it falls on it's face.  I think this is when the secondary's open but I could be mistaken. 

Timing: I've gone round and round with the timing, currently at 16 base, 18 mech advance, in by 2500. 

Plugs: Autolite 3924, gapped at .035. pic attached of what they look like.

Vacuum: I believe in the 7-9" range but I'll have to double check that.

Wondering what else I can check to see what the engine wants or needs in the higher rpm range?



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71 Malibu Convertible 408ci LS3 BBC

Edlbrk RPM Heads/intake/Holley Ultra HP 750

Custom Bullet SFT Cam

Forged pistons/cast crank/ARP rod bolts.

trans&rear: 700r4/3k stall, 3.73 posi 12 bolt 

Best 1/4 mi: 12.91 @ 104.69, 1.83 60', DA corrected 12.7 @ 106.45

dyno & 1/4mi videos: https://www.youtube.com/channel/UCbiO_bxyda5QWMDTQAuOEtg




- Mike -
Olalla, Wa


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What carb, vacuum secondary or DP? What jet and squirter sizes front and rear? Sounds like it wants more fuel.

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'66 SS Chevelle LQ4/4L80E

'65 Malibu SS (Best of 10.49 @ 130mph 1.51 60')

'31 Ford 5-window model A coupe

'58 F-100 short box fleet side big window custom cab




- Mike -
Puyallup, WA


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Definitely need more info as Mr. Parker inquired. Could need more:

-Rear jet(higher number)
-Rear squirter(higher number) and/or secondary throttle cam change.
-A different power valve rated at another level for fuel to come in sooner OR as most of us do, delete the secondary power valve and jet up the rear 8-12 sizes higher than the primary.
-A vacuum diaphragm spring change(if a vacuum secondary carb),
-Secondary blades may not be opening all the way(verify with another person when engine is off)
-Carburetor too small(you need around a 750cfm)

It could be one or a combination of things. First thing is check to make sure the blades open all the way, then take the rear bowl off and tell us what you see.




-- Edited by cobaltchev67 on Saturday 6th of December 2014 02:55:54 PM

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'67 Chevelle -- 383ci, Jerico DR4 4 speed -- 3.19 1st gearset, Gear Vendors Overdrive/Underdrive, Strange S60 w/3.54 gears

'70 Camaro -- In the works TT 6.0L, 4L80E, ??? rear end 



- GearHead -

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It's a completely stock 750 ebrock with electric choke, so whatever came in those. I supposed I could Google it unless someone knows of the top of their head? An edelbrock it's vac secondarys right?

__________________

71 Malibu Convertible 408ci LS3 BBC

Edlbrk RPM Heads/intake/Holley Ultra HP 750

Custom Bullet SFT Cam

Forged pistons/cast crank/ARP rod bolts.

trans&rear: 700r4/3k stall, 3.73 posi 12 bolt 

Best 1/4 mi: 12.91 @ 104.69, 1.83 60', DA corrected 12.7 @ 106.45

dyno & 1/4mi videos: https://www.youtube.com/channel/UCbiO_bxyda5QWMDTQAuOEtg




- wondah whooooaman-
Colorado Springs


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I think TOG is your Edelbrock tuner..................



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Mark
69 Chevelle SS
"Carpe Jugulum"
"Only those who have never learned self-restraint fear reasonable discipline" T.R. Fehrenbach

http://www.chevelles.com/showroom/data/500/showpic1.jpg
http://www.chevelles.com/showroom/da...ium/motor2.JPG
http://www.chevelles.com/showroom/data/500/breakout.JPG



- Mike -
Puyallup, WA


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Yeah...almost everybody here runs a version of the 4150 Holley. Sorry, no advice here...foreign to me...

__________________

'67 Chevelle -- 383ci, Jerico DR4 4 speed -- 3.19 1st gearset, Gear Vendors Overdrive/Underdrive, Strange S60 w/3.54 gears

'70 Camaro -- In the works TT 6.0L, 4L80E, ??? rear end 




waka-waka-waka
Orting, WA


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Any of the edelbrock carbs are painfully easy to tune. I have all the tuning stuff and the owners manual. Just follow the calibration chart and it will tell you exactly what to change. Any of the local O'Reilly stores have all the rods and jets.

__________________

1967 Turbocharged 408ci LSx Chevelle 1012 rwhp, 959 rwtq  www.67-chevelle.com

2009 Silverado Edelbrock E-Force supercharged  Silverado On the Dyno

1967 El Camino 6.0L...and the build begins!

 



- GearHead -

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I bumped the initial to 22(40total), the engine loved the increase in base, better idle meaning stronger and less likely to die coming down in rpm, and snappier throttle response of idle. The top end seemed to improve a little, so I took it to 24b & 42total and I didn't see any improvements in fact merging on the highway with my foot on the floor the engine climbs to 3500 & then just sits there and will not go any higher. I confirmed the throttle is opening fully with pedal action. Guys over on the mother-ship site are recommending I switch to holley, which I'm not opposed to, but I'd rather tweak and tune what I already have if the end result performance wise is going to be the same.

TOG was recommended by Kettbo as well, apparently I need to track this guy down?

__________________

71 Malibu Convertible 408ci LS3 BBC

Edlbrk RPM Heads/intake/Holley Ultra HP 750

Custom Bullet SFT Cam

Forged pistons/cast crank/ARP rod bolts.

trans&rear: 700r4/3k stall, 3.73 posi 12 bolt 

Best 1/4 mi: 12.91 @ 104.69, 1.83 60', DA corrected 12.7 @ 106.45

dyno & 1/4mi videos: https://www.youtube.com/channel/UCbiO_bxyda5QWMDTQAuOEtg




- wondah whooooaman-
Colorado Springs


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Posts: 3457
Date:
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SleepernSeattle wrote



TOG was recommended by Kettbo as well, apparently I need to track this guy down?


 We all need to track TOG down, there hasn't been a TOG sighting in quite a while.  In fact, there hasn't been a Loader, Special Greg, Dave, Outcast, BrIan, or BrYan sightings in a long time.

Someone needs to chew their asses for being absent!  Oh yeah, run a Holleywink



__________________
Mark
69 Chevelle SS
"Carpe Jugulum"
"Only those who have never learned self-restraint fear reasonable discipline" T.R. Fehrenbach

http://www.chevelles.com/showroom/data/500/showpic1.jpg
http://www.chevelles.com/showroom/da...ium/motor2.JPG
http://www.chevelles.com/showroom/data/500/breakout.JPG



- Jason -
Marysville, WA


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Posts: 1463
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What is the number on your Edelbrock carb, located on lower left front?

The number will tell us if you have an AVS or AFB and verify the size to help with tuning advise.

What all does your engine combo consist of?

Intake, cam specs, compression, distributor type and if running vac advance.

Jason



-- Edited by JBSS396 on Monday 8th of December 2014 05:58:59 PM

__________________

69 Chevelle SS 
454 10.4:1, Engle HFT cam 244/260 at .050", .570 lift, 850 Mighty Demon Carb, TH 350, 10" TCI 3500, 12 Bolt 373's, 28x10.5 slicks 

Best Time at Pacific 6/20/2014, 11.96 @ 110 mph.

79 Malibu: 350 with Vortec heads, Performer Intake, Q-jet, TH350, 3.31 gears

Tow rig: 82 Chev C20 Scottsdale 454



- GearHead -

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Carb #1407 1182
Intake: ebrock rpm air gap
Cam: lunati voodoo 60203 hft. Adv dur(int/exh): 268/276 @ .050 227/233. Lift(int/exh).542/554. LSA/ICL:110/106
CR 10.75:1
Dist: msd pro billet, vac advance plugged.
Msd 6A ign box and coil
Current timing: base 16° total 40° in by 2200
Let me know if there's anything else that would be helpful, thanks guys

__________________

71 Malibu Convertible 408ci LS3 BBC

Edlbrk RPM Heads/intake/Holley Ultra HP 750

Custom Bullet SFT Cam

Forged pistons/cast crank/ARP rod bolts.

trans&rear: 700r4/3k stall, 3.73 posi 12 bolt 

Best 1/4 mi: 12.91 @ 104.69, 1.83 60', DA corrected 12.7 @ 106.45

dyno & 1/4mi videos: https://www.youtube.com/channel/UCbiO_bxyda5QWMDTQAuOEtg



- GearHead -

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Base timing is 22° not 16° with 18° mechanical for total of 40°, in by 2200, no vac advance

__________________

71 Malibu Convertible 408ci LS3 BBC

Edlbrk RPM Heads/intake/Holley Ultra HP 750

Custom Bullet SFT Cam

Forged pistons/cast crank/ARP rod bolts.

trans&rear: 700r4/3k stall, 3.73 posi 12 bolt 

Best 1/4 mi: 12.91 @ 104.69, 1.83 60', DA corrected 12.7 @ 106.45

dyno & 1/4mi videos: https://www.youtube.com/channel/UCbiO_bxyda5QWMDTQAuOEtg




waka-waka-waka
Orting, WA


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Posts: 842
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1407 is the base 750. Its jetted differently than the 750 that comes from the factory with the electric choke (1411). Did you add the electric choke or did someone else? The date code is the 182nd day of 2011.

__________________

1967 Turbocharged 408ci LSx Chevelle 1012 rwhp, 959 rwtq  www.67-chevelle.com

2009 Silverado Edelbrock E-Force supercharged  Silverado On the Dyno

1967 El Camino 6.0L...and the build begins!

 



- GearHead -

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Ok that all makes sense, the engine build project was started back in 08-09 and was a slowly developing project (over the past 5 years.) So the carb was new, but doesn't surprise me it was from 2011. And while the carb looked brand new, the electric choke doesn't look new, it looks older then the carb, and the box it came in said manual choke. I have a manual for the carb but unfortunately it got covered with trans fluid and is pretty much unusable now but I think they have them available online in adobe acrobat pdf format. So are you guys thinking I need to increase the jet size in the secondary's?

__________________

71 Malibu Convertible 408ci LS3 BBC

Edlbrk RPM Heads/intake/Holley Ultra HP 750

Custom Bullet SFT Cam

Forged pistons/cast crank/ARP rod bolts.

trans&rear: 700r4/3k stall, 3.73 posi 12 bolt 

Best 1/4 mi: 12.91 @ 104.69, 1.83 60', DA corrected 12.7 @ 106.45

dyno & 1/4mi videos: https://www.youtube.com/channel/UCbiO_bxyda5QWMDTQAuOEtg




waka-waka-waka
Orting, WA


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Posts: 842
Date:
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I could rebuild 50 Edelbrock carbs with the amount of stuff I have for them. The owners manual doesn't come in the new carbs anymore. They are updating it. Right now there is a slimed down version included. I have copies of the old one if you want one. Or 100 of them. lol Like any carb, you need to make sure its not getting more than 6lbs of pressure. Its usually something overlooked and its a must. I haven't seen you mention a pressure regulator yet.



-- Edited by Bonehead on Tuesday 9th of December 2014 12:57:04 PM

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__________________

1967 Turbocharged 408ci LSx Chevelle 1012 rwhp, 959 rwtq  www.67-chevelle.com

2009 Silverado Edelbrock E-Force supercharged  Silverado On the Dyno

1967 El Camino 6.0L...and the build begins!

 



- GearHead -

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Posts: 242
Date:
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No I do not have a regulator, think I'm running about 7psi at idle right now, could this be my.issue?

__________________

71 Malibu Convertible 408ci LS3 BBC

Edlbrk RPM Heads/intake/Holley Ultra HP 750

Custom Bullet SFT Cam

Forged pistons/cast crank/ARP rod bolts.

trans&rear: 700r4/3k stall, 3.73 posi 12 bolt 

Best 1/4 mi: 12.91 @ 104.69, 1.83 60', DA corrected 12.7 @ 106.45

dyno & 1/4mi videos: https://www.youtube.com/channel/UCbiO_bxyda5QWMDTQAuOEtg



- GearHead -

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Date:
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I just called ebrock tech line, I have the 1712 pump which does not require a pressure regulator. I described my issue to the tech guy and he was leaning toward a delivery issue. He said I should extended my fuel psi gauge to an area I could see it while driving and confirm my pressure isn't dropping when I experience these issues. Off to the parts store for some fittings.

__________________

71 Malibu Convertible 408ci LS3 BBC

Edlbrk RPM Heads/intake/Holley Ultra HP 750

Custom Bullet SFT Cam

Forged pistons/cast crank/ARP rod bolts.

trans&rear: 700r4/3k stall, 3.73 posi 12 bolt 

Best 1/4 mi: 12.91 @ 104.69, 1.83 60', DA corrected 12.7 @ 106.45

dyno & 1/4mi videos: https://www.youtube.com/channel/UCbiO_bxyda5QWMDTQAuOEtg




waka-waka-waka
Orting, WA


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Posts: 842
Date:
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That's a victor series pump and 7 is definitely way too much. Set it at 6 and tune from there.

__________________

1967 Turbocharged 408ci LSx Chevelle 1012 rwhp, 959 rwtq  www.67-chevelle.com

2009 Silverado Edelbrock E-Force supercharged  Silverado On the Dyno

1967 El Camino 6.0L...and the build begins!

 




- Jason -
Marysville, WA


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Posts: 1463
Date:
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Just to check all bases, make sure when the car is warmed up and this problem is present that the choke flap is all the way open and you have a good 12V key on source to the electric choke.

It's been a while since I've had an Edelbrock carb but most carbs have a secondary lockout when the choke is still on.

__________________

69 Chevelle SS 
454 10.4:1, Engle HFT cam 244/260 at .050", .570 lift, 850 Mighty Demon Carb, TH 350, 10" TCI 3500, 12 Bolt 373's, 28x10.5 slicks 

Best Time at Pacific 6/20/2014, 11.96 @ 110 mph.

79 Malibu: 350 with Vortec heads, Performer Intake, Q-jet, TH350, 3.31 gears

Tow rig: 82 Chev C20 Scottsdale 454



- GearHead -

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Sorry that should've read 1722. You know I do need to check my choke blade since it was added later on. That seems like a very likely cause. What do you mean by a secondary lockout? Also I just put a tee in where fuel psi gauge is, so I kept one gauge by the carb then ran a hose up to a second gauge that I mounted under the cowl and can be easily seen from the driver's seat. This way I can confirm I'm not losing(or gaining lots of) psi while I'm experiencing this issue.

__________________

71 Malibu Convertible 408ci LS3 BBC

Edlbrk RPM Heads/intake/Holley Ultra HP 750

Custom Bullet SFT Cam

Forged pistons/cast crank/ARP rod bolts.

trans&rear: 700r4/3k stall, 3.73 posi 12 bolt 

Best 1/4 mi: 12.91 @ 104.69, 1.83 60', DA corrected 12.7 @ 106.45

dyno & 1/4mi videos: https://www.youtube.com/channel/UCbiO_bxyda5QWMDTQAuOEtg

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