holley sec powervalve
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holley sec powervalve

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    Senior Member rogerroost's Avatar
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    Default holley sec powervalve

    So from what I've read here,if I understnd correctly, It's common to plug the sec powervale on my 850 4150 ? is it that simple,just plug the threaded hole,don't worry about the 2 small holes on either side?
    Is this a mod a guy should just do,having not yet run this motor ?
    460 ,280 comp cam ,9.6:1,basset o/t's& stealth intake.
    thanx

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    Senior Member Ronboats's Avatar
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    If the motor runs good ,leave it alone. But if you do decide to plug it(there is a special solid power valve plug, thats all you need to plug) dont forget you will need to increase the secondary jets by about 8 sizes to make up for the fuel you are plugging off.It will run richer at idle because of this, so you may not like it set up that way. The carb was built with the valve for a reason. Just try it first.

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    Senior Member rogerroost's Avatar
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    thanks ronboat,so why do guys plug it? Whats the benifit? the"special plug" is what I was wondering about

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    Senior Member Ronboats's Avatar
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    Why plug it? I don't know. I tried it once on my car, but it idled way too rich. I think Jegs sells those plugs if you wanted to try it.I think maybe guys plug it and increase the jet size if thier valve isnt opening soon enough,causing a bog as the thottle is opened-kind of a band-aid fix. Better to get the proper size valve if you get this problem.( probably a higher number valve that opens sooner if there is a bog)

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    northern member Canuc's Avatar
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    Ronboats right if the carb had one from holley it should be the way to go on your 460 . for racing you can plug it if you don't want to lean the secondaries .
    Quote Originally Posted by gn7 If your ran a cammer your odds of finishing WERE ZERO.

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    Senior Member rogerroost's Avatar
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    thanx for the advice . hey Canuc,you don't by chance have a brother Brian do you ?

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    northern member Canuc's Avatar
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    nope no Brian
    Quote Originally Posted by gn7 If your ran a cammer your odds of finishing WERE ZERO.

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    Senior Member Schiada 201's Avatar
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    Leave it alone, it can be a nightmare.

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    Senior Member Bubbletop409's Avatar
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    Quote Originally Posted by rogerroost View Post
    So from what I've read here,if I understnd correctly, It's common to plug the sec powervale on my 850 4150 ? is it that simple,just plug the threaded hole,don't worry about the 2 small holes on either side?
    Is this a mod a guy should just do,having not yet run this motor ?
    460 ,280 comp cam ,9.6:1,basset o/t's& stealth intake.
    thanx

    I would be surprised if you found a power valve on the secondary side of an 850. They are usually on the primairy side to enrichen the mixture at full throttle, only reason to remove is usually in a full race application, however some improvement could result from replacing a faulty or incorrect PV. They are rated to open according to a drop in vacumn.
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    Most Holley 850 DP carbs will have one on the secondaries

    Can cause leaning if Lateral or Acc G's are reasonable, its alot higher than the main jets and will become uncovered quicker due to fuel slosh than the main jets. This isnt usually a problem on the primary side as the Acc G's force the fuel towards the PV and main jets, forced away on the sec side
    (assumes normal carb mount direction)

    People with sideways mounted on T-rams may want to think about this (if concerned with straight line running only)

    Amazing to see people put secondary jet extensions in and leave the PV to its own demise.
    Pretty much a no brainer on a hard leaving drag car to remove and rejet to compensate

    On a boat probably only nessacerry if pulling over 1 G Acc or over 1.5 G lateral, definitly shows up at 2 Lateral G's and above

    Fill your carb with fuel to the correct level then tilt it sideways and for - aft and see what angle you can get it to before fuel pours out of the boosters (this is static only without any intake vac pulling on the booster)

    Most holleys pour fuel at around 20-22 degrees lateral tilt, when you can get a carb to 45 degrees without this happening you are on your way

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    Senior Member Ronboats's Avatar
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    Quote Originally Posted by Redskin12 View Post
    Most Holley 850 DP carbs will have one on the secondaries

    Can cause leaning if Lateral or Acc G's are reasonable, its alot higher than the main jets and will become uncovered quicker due to fuel slosh than the main jets. This isnt usually a problem on the primary side as the Acc G's force the fuel towards the PV and main jets, forced away on the sec side
    (assumes normal carb mount direction)

    People with sideways mounted on T-rams may want to think about this (if concerned with straight line running only)

    Amazing to see people put secondary jet extensions in and leave the PV to its own demise.
    Pretty much a no brainer on a hard leaving drag car to remove and rejet to compensate

    On a boat probably only nessacerry if pulling over 1 G Acc or over 1.5 G lateral, definitly shows up at 2 Lateral G's and above

    Fill your carb with fuel to the correct level then tilt it sideways and for - aft and see what angle you can get it to before fuel pours out of the boosters (this is static only without any intake vac pulling on the booster)

    Most holleys pour fuel at around 20-22 degrees lateral tilt, when you can get a carb to 45 degrees without this happening you are on your way
    HUH??? What do you mean by getting it to tilt without fuel pouring out the boosters?Why would fuel pour out the boosters??And what do you suggest as the "cure"? And what does this have to do with the power valve or jets?

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    Quote Originally Posted by Ronboats View Post
    HUH??? What do you mean by getting it to tilt without fuel pouring out the boosters?Why would fuel pour out the boosters??And what do you suggest as the "cure"? And what does this have to do with the power valve or jets?
    It related directly to the rest of my post and the uncanny ability of the rear PV (the topic) to become uncovered during operation (hence the desire to remove it and recalibrate in some instances)

    Just trying to get people to think about what actually happens to the fuel in their carbs when its not sitting on the trailer, on the dyno or the workshop bench (ie in a boat or vehicle)

    Take the carb off or use a spare, holding it in your hand over a catch tray tilt the carb 45 degrees backwards with fuel in it and see what happens (rough approximation of operating under 1G of acceleration) The fuel will pour out of the primary boosters and on the secondaries run away from the metering block to the back of the bowl and uncover the rear PV before it uncovers the rear jets.

    (and your imaginary engine emits a lean cough, stumble with an open rear PV sucking air instead of 6-10 jet sizes of fuel into your already emulsified mixture in the secondary main wells)

    Now refill the fuel bowls and tilt it sideways 45 degrees and observe again (rough approx of 1 lateral G)

    It has everything to do with the main jets and more so the PV, especially the rear one.

    Have a look at this rough diag with the same amount of fuel trapped in a Holley bowl when subjected to different lateral G's

    Although different to the Accel issue with a rear PV, what effect do you think the differing fuel heights "stacked" against the two main wells have on the boosters ability to draw fuel (ignoring the fact that even under no intake vac, raw, unatomised fuel will pour from the boosters on one side of the carb under any moderate lateral G's)

    Just trying to give a "real world" reason as to why you may or may not want to delete the rear PV and instances where its desirable

    Altough this diag doesnt show what happens under Acceleration look at the height of the PV (plugged in this instance) Vs the main jets and think "why bother with jet extensions, if my 850 Holley has a rear power valve, that will be the first to uncover during acceleration"
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    Last edited by Redskin12; 11-14-2009 at 08:06 PM.

  15. #13
    Senior Member GT Jets's Avatar
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    Secondary PV removal is a common practice umong the Rock Dodger (white water boats) because of the way they sometimes run.

    Redskin 12 is "on the money" with the reasoning behind it...

    The PV cannot do it's job if it's dry....

    Check this out! There are many more video's and pictures that show extreme hull angles while getting these badboys on plane, while doing that, tha rear bowl runs damn near dry and leans them to the point of disaster...Happens often.

    GT


    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

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    Good example GT Jets

    There are alot of ways of creating the same fuel issue with different types of boats and vehicles

    The main issue I have is large lateral G's (over 3) and Accel G's at the start of a race. Even though the boat sits fairly flat in corners the large lateral G's make the carb (class restriction) act like its lying on its side LOL !!!!

    Another video example of my boat putting a carb under these conditions

    No rear PV by the way even though the carb came with one


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