Re: 8896 3 circuit rich down low
[Re: roadhazard]
#1875074
07/21/15 02:31 PM
07/21/15 02:31 PM
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Joined: Nov 2009
Posts: 3,410 Belpre,Ohio
CHAPPER
master
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master
Joined: Nov 2009
Posts: 3,410
Belpre,Ohio
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I had the same issue with my old 8896 until I sent it to Thumperdart. It would kill plugs in no time at idle & cruise. So I had him modify and install some new 2 circuit metering blocks and 12 hole boosters along with the other modifications he does and could not be happier with what I received back from him. I have one identical to this from Thump....my results were the same. Sad thing,,,my block cracked first time to the track after installing it. Putting new motor together now. Probably be Fall before I get to try it some more.
If you like drag racing, support your local track.
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Re: 8896 3 circuit rich down low
[Re: AndyF]
#1875103
07/21/15 03:22 PM
07/21/15 03:22 PM
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Joined: Jul 2004
Posts: 19,318 State of confusion
Thumperdart
I Live Here
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I Live Here
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Posts: 19,318
State of confusion
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One very easy trick to try is to take the intermediate air bleeds out and see how it runs. Holley left them out on at least one version of the 3 circuit 4500 so there is some history behind that thought.
It would be helpful if you had a wideband when you try stuff like this but even without a wideband you should be able to tell if you're on the right path by how the engine sounds.
A set of billet metering blocks is probably your best investment if you want to dial the carb in yourself. Otherwise you can send the carb in and get it sorted out for you. Removing the int. bleed is a band-aid at best and I have two 2-circuit conversions on 8-second street/strip cars that will never go 3 again.......no need to.
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
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Re: 8896 3 circuit rich down low
[Re: Dodgem]
#1875131
07/21/15 04:14 PM
07/21/15 04:14 PM
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Joined: Jan 2003
Posts: 13,416 Marion, South Carolina [><]
an8sec70cuda
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I Live Here
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Marion, South Carolina [><]
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The 8896 dominator on the Camaro was a pig when we first started w/ it. Removing the int. air bleed definitely helped a lot. Ended up getting a set of billet blocks from Quick Fuel, still 3 circuit, and leaned out the int. circuit. It made a big difference and is a lot better now, but still needs improving.
CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 18 spline 4 speed, Dana 60 '71 Demon, 340, low gear 904, 8.75 '73 Chrysler New Yorker, 440, 727, 8.75 '90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt '06 GMC 2500HD LBZ Duramax
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Re: 8896 3 circuit rich down low
[Re: an8sec70cuda]
#1875179
07/21/15 05:32 PM
07/21/15 05:32 PM
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Joined: Jan 2003
Posts: 31,106 Oregon
AndyF
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I Win
Joined: Jan 2003
Posts: 31,106
Oregon
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Yep, that is a fairly typical sequence for tuning a Holley 3 circuit. First remove the intermediate air bleeds, then buy billet metering blocks, then switch to a 2 circuit!
For a street car a person can also put power valves in both primary and secondary just to lean out the main circuit some more. If you have the billet metering blocks then the next trick to try is to make the PVCR larger and the main jets smaller to try and get the cruise AF lean.
The intermediate circuit can be very difficult to get right in a street car since the throttle position will heavily influence how much fuel gets pulled out of the dump tubes. Worst case is when you're driving down the freeway and the throttle blades are pointed right at the dump tubes and the intake vacuum is just sucking fuel out of the bowls.
The intermediate circuit was designed for NASCAR use so no surprise that it doesn't work very well in other uses.
Last edited by AndyF; 07/21/15 05:33 PM.
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Re: 8896 3 circuit rich down low
[Re: Dodgem]
#1875180
07/21/15 05:37 PM
07/21/15 05:37 PM
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Joined: Jan 2003
Posts: 13,416 Marion, South Carolina [><]
an8sec70cuda
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I Live Here
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Posts: 13,416
Marion, South Carolina [><]
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I agree Andy. I tried to talk the owner into doing the 2 circuit conversion, but he went ahead and bought the 3 circuit blocks from QF. Hey, I just drive and wrench on the car...he pays for it, lol. It is a race only car though, so it's not critical we get it razor sharp. It runs great at WOT, goes up on the transbrake real nice, and idles clean. The tuning we've done has made it a lot cleaner, but it could definitely be better.
CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 18 spline 4 speed, Dana 60 '71 Demon, 340, low gear 904, 8.75 '73 Chrysler New Yorker, 440, 727, 8.75 '90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt '06 GMC 2500HD LBZ Duramax
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Re: 8896 3 circuit rich down low
[Re: an8sec70cuda]
#1875582
07/22/15 05:25 AM
07/22/15 05:25 AM
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Joined: Jan 2003
Posts: 5,992 Anoka County, MN
Leigh
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Posts: 5,992
Anoka County, MN
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Monte offered a good tip. A 3 circuit is a tuning tool, to get the car on the converter. For part throttle, transitory use, not so good. I struggled with one leaving at 3,000. The 2 circuit 1050 I use now, is clean as can be. AND, not to sound like a broken record, those 8896 metering blocks, with the idle feed tube in them, suck. Has this been changed yet?
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Re: 8896 3 circuit rich down low
[Re: Dodgem]
#1875633
07/22/15 10:39 AM
07/22/15 10:39 AM
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Joined: Dec 2014
Posts: 304 Florida
Mark Whitener
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enthusiast
Joined: Dec 2014
Posts: 304
Florida
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There are rare instances where a the intermediate circuit can be useful, but most will never need it. The intermediate circuit was designed specifically for an IR manifold, and can be useful on a 4 or 6 cylinder comp engine where plenum pulsing is high enough to disrupt low RPM and part throttle booster signal. On an occasion it can be helpful on an under carb stop, if the engine is large enough to force the stop blades to close too far, but it takes less fuel than most 3 circuit carbs come with to do the trick in those few cases. As far as using it to come up on the converter, if you use a decent booster it's never an issue.
Mark Whitener [url=www.racingfuelsystems.com[/url]
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Re: 8896 3 circuit rich down low
[Re: Dodgem]
#1876438
07/23/15 09:44 AM
07/23/15 09:44 AM
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Joined: Dec 2014
Posts: 304 Florida
Mark Whitener
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enthusiast
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Posts: 304
Florida
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Everything about making any carb work well is in getting a relatively homogeneous mix and equal distribution. When you do you can run a larger carb, use less fuel, and run less timing, all while making more power. Booster selection is for me the most important factor in accomplishing this. When you design the booster correctly for the carb emulsion becomes insignificant other than correcting the fuel curve, and an intermediate circuit only hurts this by dumping a load of fuel out of a tube. Methanol is an exception, with a larger style Dominator the intermediate can be used to ensure sufficient fuel as the main circuit passages can be restrictive. However on these I move the discharge tube, makes the intermediate more of an auxiliary main.
Mark Whitener [url=www.racingfuelsystems.com[/url]
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Re: 8896 3 circuit rich down low
[Re: AndyF]
#1893617
08/17/15 04:01 PM
08/17/15 04:01 PM
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Joined: Mar 2008
Posts: 5,746 Ontario, Canada
Dodgem
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Ontario, Canada
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Usually have to put a smaller intermediate jet in it rather than changing the air bleeds. The 3 circuit carbs I've worked on usually require at least 10 jet sizes taken out of the intermediate circuit. Just thinking on this could you not block the intermediate jets and just jet up the mains?? Thanks again In advance.
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