Power Valve Question???
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Power Valve Question???

  1. #1
    Super Moderator HammerDown's Avatar
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    Default Power Valve Question???

    I just picked-up a 'new' Holley 850-VS list-80531 > it comes out of the box with (4.5 primary) and (3.5 secondary)
    P-jetting 78
    S-jetting 82

    The carb I'm taking-off is a Holley 850 DP list-9380(annular) with the rear PV blocked, and jetted-up.

    Question > should I assume the vacuum signals from the 850/DP and the new 850/VS will be the same or, do I have to hook-up a vacuum gauge again with the VS/850 and take cruise/wot readings all over again???

    Reason I ask > I would like to simply move the primary PV used in the 'DP' over to the new 'VS' 850.
    As for the secondary side, I may or may-not plug and jet-up...don't know yet.

    One last thing > this 'new' 850vs has brass floats > run'em or install the plastic floats?

    Thanks for and feedback, Ray
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

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    Senior Member SBS933's Avatar
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    If this is for a jet you don't want a power valve in the secondaries.

  4. #3
    Senior Member EVILFORCE's Avatar
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    I like power valves. Unless it is a race application. Can save some fuel.
    No Fool Like A Old Fool is there?

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  6. #4
    gn7
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    I think I would try the DP's PV in the primaries, I'm guessing its a 6.5 in the DP, and move the 4.5 from the VS's primary to the secondary. The PVs in the VS carb are set up for a car, and seemingly for MILAGE unless your foot is stuffed it. I would keep an eye on the plugs for a jetting. Even checking them after a part throttle cruise and a clean shut down. Its probably set up a little lean in the part throttle cruise with the PVs closed.



    You may end up with the secondary PV blocked, but with the vac secondary, I think I would give the secondary PV a try. If your slowly open the throttle and feel it lay over a little as the secondaries come in, you'll know that either you need a higher PV number, or remove it and jet up.



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    Super Moderator HammerDown's Avatar
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    Great feedback...THANKS!
    Evil, I too am looking for better, higher RPM fuel mileage and I know it's there > another reason for going back, to a VS carb.
    SBS93 > I question your post as to why??? Yes this is a 468 Jet.
    GN, as usual your input is always noted

    At this posting I don't recall the # primary-pv used in the 850-DP, I'll check it tomorrow.
    However, the PV's in the 'new' 850-VS are way low > this I know for sure.

    I just didn't know if the 'vacuum signal to both 850's would be the same??? and the reason for my post.

    One thing I do know (from research) the list-9380, 850 'annular' dumps more fuel vs a 'down-leg' 850-dp. Thus preferred on a track engine squeezing out every bit of ET...and NOT what I care about.

    Thanks again, Ray
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

  8. #6
    gn7
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    Quote Originally Posted by HammerDown View Post
    Great feedback...THANKS!
    Evil, I too am looking for better, higher RPM fuel mileage and I know it's there > another reason for going back, to a VS carb.
    SBS93 > I question your post as, for over a decade I ran a 715-vs and it worked flawlessly and sipped fuel! Yes this is a 468 Jet.
    GN, as usual your input is always noted

    At this posting I don't recall the # primary-pv used in the 850-DP, I'll check it tomorrow.
    However, the PV's in the 'new' 850-VS are way low > this I know for sure.

    I just didn't know if the 'vacuum signal to both 850's would be the same??? and the reason for my post.

    One thing I do know (from research) the list-9380, 850 'annular' dumps more fuel vs a 'down-leg' 850-dp. Thus preferred on a track engine squeezing out every bit of ET...and NOT what I care about.

    Thanks again, Ray
    The manifold vac for both carbs will be very close at the same blade angle. Both on the primary and secondary. But with the vac secondary you can adjust when the secondaries come into play. You have to be carefull though because if you get the spring too heavy the secondaries won't open 100% and you'll lose top end RPM.
    The annular boosters will dump more fuel with the same vac signal and jet size, They are simply more active, specially at lower pressure drop. The annular can be a great milage carb, but it takes some jetting and air bleed work to get them that way.

    Keep in mind that the 80531 is a 50 state legal, C.A.R.B. approved replacement carb. Therefore, it will be lean in the part throttle ranges, more so on the primary side9note jet size). Thats also the reason for the secondary power valve and the LOW vac numbers. Low fuel usage cruising on the primaries, alittle more jet when you get into the secondaries, and even more when the vac drops low enough to aactivate the PVs. It works, but milage is one thing, torched pistons is another. So take you time and keep an eye on the plugs. I know you know how to read a plug, you shown that on the forums before.



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  9. #7
    Super Moderator HammerDown's Avatar
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    Hey Bob, just checked the 850 Annular.
    Out of the box it's jetted 78-square w/6.5 pv's (ran like shit too)

    Jetting now is 81-p & 86-s
    front PV 8.5
    rear-blocked

    *Noted vacuum readings w/850 DP/annular
    idle 13"
    2500 15"
    3000 14"
    3500 11"
    4000 8"
    5400/wot 4"


    *The stock 'primary' PV was too low a number for my vacuum reading 'before the DP secondaries opened at 4100' > thus it nosed down/lean just before the mechanical secondaries kicked-in. I remember you and I talking about this some time ago.
    You gave me some great advice setting up the 850 annular.
    It could have only gotten better (economically) with O2/exhaust readings but I run 'wet-headers'.

    Glad I found my notes...this will help setting up the 850 VS carb
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  10. #8
    gn7
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    If those are the numbers from you 850DP then the chances are you whould have never opened the 3.5 PV in the secondary of the VS carb. I have my doubts whether the moving the primary 4.5 PV to the back will help al that much. I think I would jet the primary of the VS the same as you had the DP, install the original 6.5 you had in the DP into the secondaries of the VS. The last think you need is for the secondary PV to close when you flat out. The 4.5 will open when the secondaries first open. But as the Rs climb the vac is going to climb with it and the PV could possibly close.

    BTW. I know you're looking for milage, but the 4.00 of vac at 5000 tells you that the carb is a little small for max performance. 1-1.5 is more in the max performance range.



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    Last edited by gn7; 09-25-2012 at 01:15 PM.

  11. #9
    Super Moderator HammerDown's Avatar
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    ^ great feedback Bob...
    I remember wanting to try a different vacuum gauge for comparison, but never did
    Ugh, then I need a BIGGER carb eh
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

  12. #10
    gn7
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    You probably would gain much from a bigger carb. Maybe a little acceleration, but not alot on the top end speed.
    Just thought I would inform you knowing how you're looking for a little extra fuel milage. You can't have both. Feel fortunate. My deal eats roughly a gallon a minute of 116. And our races aren't 5 minutes long, or those cute little 1/4 mile squirts.



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  13. #11
    Super Moderator HammerDown's Avatar
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    Quote Originally Posted by gn7 View Post
    You probably would gain much from a bigger carb. Maybe a little acceleration, but not alot on the top end speed.
    Just thought I would inform you knowing how you're looking for a little extra fuel milage. You can't have both. Feel fortunate. My deal eats roughly a gallon a minute of 116. And our races aren't 5 minutes long, or those cute little 1/4 mile squirts.
    Mean 'wouldn't' gain much?

    I know I can't have "both"...and if a BIGGER carb would NOT give gains in RPM or top-end speed...then I don't need or want it

    Your gn7 boats fuel consumption and cost of doing so has me in the fetal position
    But having your knowledge in building me a bad-ass lake motor would be Bad-A$$
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  14. #12
    gn7
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    Quote Originally Posted by HammerDown View Post
    Mean 'wouldn't' gain much?

    I know I can't have "both"...and if a BIGGER carb would NOT give gains in RPM or top-end speed...then I don't need or want it

    Your gn7 boats fuel consumption and cost of doing so has me in the fetal position
    But having your knowledge in building me a bad-ass lake motor would be Bad-A$$
    Ooops. Yes wouldn't make a huge difference. I assure you, anything you gained you wouldn't think was worth it.

    With the GN Its not just fuel costs. The engines don't last all that long either, if when they stay to gether.



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