Re: Help With Holley 850 Ultra Double Pumper Tune Up
[Re: Beep Beep]
#2094559
06/19/16 06:59 PM
06/19/16 06:59 PM
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Joined: Nov 2011
Posts: 2,154 Its a TRAP!
DARTH V8Я
Oh No!! I just had a moron attack!
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Oh No!! I just had a moron attack!
Joined: Nov 2011
Posts: 2,154
Its a TRAP!
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Gotta jet for that carb. Try a couple sizes down on the primary. Vacuum advance dizzy? If not, try one.
When it takes more than a sweet mullet to prove you rule at the trailer park..
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Re: Help With Holley 850 Ultra Double Pumper Tune Up
[Re: Beep Beep]
#2094604
06/19/16 09:06 PM
06/19/16 09:06 PM
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Joined: Jan 2003
Posts: 12,256 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
Joined: Jan 2003
Posts: 12,256
Benton, IL.
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Double pumpers are pig rich on the transitions and at cruise. They are jetted for the track. The simplest thing to try is to drop down 5 jets on the primary and open the PVCRs several thousands to compensate. You need a wide band to re-balance the WOT.
Shoot for mid 14s for the cruise, but you will need the enrichment circuit to come in sooner with that leaner and cleaner cruise. Probably an 8.5 to 10.5 power valve. You can disconnect the secondary linkage so that you can concentrate on the primary mixes. The secondary WOT is usually pretty close.
Master, again and still
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Re: Help With Holley 850 Ultra Double Pumper Tune Up
[Re: Beep Beep]
#2094686
06/19/16 11:41 PM
06/19/16 11:41 PM
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Joined: Feb 2007
Posts: 749 NY
Beep Beep
OP
super stock
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OP
super stock
Joined: Feb 2007
Posts: 749
NY
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I will have to double check the A/R at 3500-4000 but I am pretty sure it is 11.5 to 12.5. The high speed air bleeds are fixed. Were are these idle feeds located? I have the billet metering blocks.
Last edited by Beep Beep; 06/19/16 11:48 PM.
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Re: Help With Holley 850 Ultra Double Pumper Tune Up
[Re: krautrock]
#2094705
06/20/16 12:13 AM
06/20/16 12:13 AM
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Joined: Jan 2003
Posts: 27,421 Balt. Md
383man
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,421
Balt. Md
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i would first work on the idle feed restrictors (IFR's) and the primary jets (the 3500-4000 rpm cruise that justinp61 mentioned). This is what I would do first. If you think about it when you are cruising most of the time you are running of the transfer slot circuit which can be leaned out by the idle feed restriction. I know most of my part throttle cruising I am running on the tranfer (transistion) slots so if its fat at part throttle cruise I would lean out the (IFR) idle feed restrictions. If you are happy with the rest of the carbs settings then leaning the idle feed restrictions wont effect the other circuits but you may just have to adjust your mixture screws when done. I believe most billet metering blocks should have jets for the IFR. In the older carbs we would put a small piece of wire in the IFR which also would lean it out some. But I believe yours should have jets in them already. They (the IFR) can also be drilled and have jets installed in them as "Hemmings Muscle Machines" mag had an article about doing that a few months back. Ron
Last edited by 383man; 06/20/16 12:15 AM.
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Re: Help With Holley 850 Ultra Double Pumper Tune Up
[Re: Beep Beep]
#2094840
06/20/16 09:36 AM
06/20/16 09:36 AM
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Joined: Oct 2003
Posts: 11,686 W. Kentucky
justinp61
I Live Here
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I Live Here
Joined: Oct 2003
Posts: 11,686
W. Kentucky
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I will have to double check the A/R at 3500-4000 but I am pretty sure it is 11.5 to 12.5. The high speed air bleeds are fixed. Were are these idle feeds located? I have the billet metering blocks. If it's that rich I'd pull two jet sizes out of the primaries and recheck. Do this before you mess with the ifr's. Changing the primary jets will affect the cruise afr's, at least it does on mine. What Ultra do you have? I thought they all had screw in air bleeds.
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Re: Help With Holley 850 Ultra Double Pumper Tune Up
[Re: Beep Beep]
#2094874
06/20/16 11:18 AM
06/20/16 11:18 AM
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Joined: Jan 2003
Posts: 12,256 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
Joined: Jan 2003
Posts: 12,256
Benton, IL.
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A 500" engine with an 850 carb will likely cruise on the main circuit not the idle circuit. Although the OP should check to be sure. But he said that his idle is good, so leaning his IFRs is not a good place to start in my opinion. Besides, the main jets are the only items that screw in. Everything else requires drilling and threading in order to adjust. (Of course there are always wires.......)
The PVCRs do not have to be drilled at first. The mains can be dropped down how ever many sizes you wish and then the cruise A/F checked. But if the mains end up needing to be sized down, then the PVCRs will need to be enlarged to compensate.
Again, I think that the easiest and best start would be to disconnect the secondary linkage, drop down several main jet sizes and test drive the cruise. Just be aware that the power circuit will be lean until the PVCRs are opened up.
Master, again and still
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Re: Help With Holley 850 Ultra Double Pumper Tune Up
[Re: Beep Beep]
#2094877
06/20/16 11:29 AM
06/20/16 11:29 AM
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Joined: Jun 2006
Posts: 5,166 CT
GTX MATT
master
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master
Joined: Jun 2006
Posts: 5,166
CT
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I have an 850 DP with the annular boosters and spend most of my time cruising on the transition circuit... This is on a stock stroke engine though.
Now I need to pin those needles, got to feel that heat Hear my motor screamin while I'm tearin up the street
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Re: Help With Holley 850 Ultra Double Pumper Tune Up
[Re: Beep Beep]
#2095155
06/20/16 06:42 PM
06/20/16 06:42 PM
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Joined: Jan 2003
Posts: 27,421 Balt. Md
383man
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,421
Balt. Md
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My point was that if the carb is jetted good for power right now I sure would not be dropping jet sizes for a cruise problem that I bet is mostly all on the transistion circuit. Once my carb was jetted at the track for power I am not going to jet down. I would lean down the IFR which is no big deal on a Holley type carb. Lean it a small amout and you should still be able to adjust your mixture for a good idle as I did on mine. But if you feel your rich all over then yea I would jet down then. Myself I like to jet my carb for best power and mph and then work the other circuits to fine tune it for cruise and idle. That way you are not affecting you power jetting. Also make sure the power valve is coming in at the right time but I dont think it will be open on a part throttle cruise unless you have it way off. I know when I cruise at part throttle I barely have the gas pedal pushed down any. Why would you want to set the idle and cruise without having the main jetting right first ? If you tune the cruise and idle circuits and then find you need to jet up at the track for power you then may have to retune the other circuits. I tune for full power first so I know I wont be changing my main jets and affecting my full power. Ron
Last edited by 383man; 06/20/16 06:55 PM.
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Re: Help With Holley 850 Ultra Double Pumper Tune Up
[Re: Beep Beep]
#2095392
06/21/16 12:51 AM
06/21/16 12:51 AM
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Joined: Jan 2003
Posts: 2,094 central texas
krautrock
top fuel
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top fuel
Joined: Jan 2003
Posts: 2,094
central texas
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Andy, I have the billet metering blocks now, but I guess you are referring to the removable IFR's on the billet blocks.
Should I go back to the 6.5 power valve or leave the 4.5 ? the 6.5 PV is probably closer to what you need. the billet blocks, it seems they would have replaceable IFR's... i will see if i can find a link to tapping the IFR's in the low psoition and post it here. most people agree the low position works better. also, you have a PV and the jetting is the same on all four ocrners of the carb??? where did the carb come from? is there a PV on the secondary side too?
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Re: Help With Holley 850 Ultra Double Pumper Tune Up
[Re: Beep Beep]
#2095397
06/21/16 12:57 AM
06/21/16 12:57 AM
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Joined: Jan 2003
Posts: 2,094 central texas
krautrock
top fuel
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top fuel
Joined: Jan 2003
Posts: 2,094
central texas
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what is the part number for the carb? do you know what the baseline jetting was?
Last edited by krautrock; 06/21/16 01:09 AM.
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