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Thread: Power Valve?

  1. #1
    custom-cruiser
    How do you Boost reference a power valve?
    I'm putting a little Wieand (177) blower on the Howard. It has mild 454 and I want to use my 750 cfm Double pumper. How much should I jet up and what do you do with power valve http://free.***boat.net/ubb/confused.gif

  2. #2
    Terrible Buddhist
    just ran into this problem with my turbo setup...how do YOU boost reference? YOU don't. You have to send the carb off to get boost referenced..they go in and drill out the carb so it will receive signal under boost.
    I have heard you can remove the powervalve and change the jetting around, but that is kind of a half a$$ sollution. Walts Hot Boat in California took care of me real well when I had this done. Getting a carb referenced is not cheap, but he gave me a real good deal through a company he works with.

  3. #3
    mister460
    You don't need to boost reference with a roots blower. You just need it adjusted to run with the blower. A carb on top of a blower recieves vacuum almost just like a normal aspiration engine. Boost referencing is for when you have boost going into the top of a carb(blow through.) Just ask a shop and they'll let you know what jets you need to run.

  4. #4
    skijake
    My understanding, but I may be wrong is that if you are running a blower with an innercooler you still need to boast referance because of the delta pressure bellow of the innercooler.
    I see some do and some don't but to me it makes sense because you can be 3 lbs less boost on the engine side of the innercooler.
    I use C&J Engineering in Norwalk Ca. for my carbs and they do referance the boost.
    Just my two cents

  5. #5
    Terrible Buddhist
    I am running a draw through...and believe me I had to have my carb boost referenced...a hard lesson learned. Just think about it...a powervalve works off vacuum...boost is the opposite of vacuum...this makes the powervalve stay shut instead of opening it. a blow through needs even more work than a draw through system does.

  6. #6
    sgdiv7
    I just went through this with my boat, you must have the manifold referenced power valves because the motor will run lean under full throttle because there is still to much vacume under the carbs where is there is psi. in the manifold to force the power valves open. this was how it was explaned to me by holley.
    Bill

  7. #7
    Clutch
    Hey sgdiv 7
    I've ran a blower w/ 2 Predators and had no problem but why, if the vac is too strong at rpm can't you block the power valve and go up about 4 jet sizes on the seconderies?

  8. #8
    custom-cruiser
    Thanks for all the replies!
    Well I just got off the phone with the Holley tech boys and they basiclly said that I do need to provide a "Manifold" boost reference to the primary power valve only. and you do that by pluging the Power Valve vacuum port in the bottom of carb then drilling a hole thru carb base that hits the original vacuum port, tap in some kind of tube then run a line down to your manifold or "T" it into a boost guage. Then go up 3 jet sizes. http://www.goldenplasma.f2s.com/foru...ies/jump03.gif

  9. #9
    sgdiv7
    Hey clutch,
    you could do that but it is 6 sizes, but the problem is the power valve is the enrichment for wide open throttle. so if you jet the carb for wide open throttle then your going to rich when your not at wide open throttle. then you will kill your fuel milage and mabe foul out plugs if you have a week ign. system. the carbs you have they need vacume to operate the air door because the needle pulls out further to give a richer mixture. I was going to use them carbs but a guy I know talked me out of them because he said you could never get the fuel curve right. I have 2 950hp holleys on top of 871 supercharger and they work great.

  10. #10
    Clutch
    Hey sgdiv7,
    8-71 umm someday, but anyway by jetting the seconderies how will that affect your low speed and idle? Unless your in them all the time?Do you still have the preds? or did you never get them. Mine work great on my motor there too simple.P.S. How do oyu put those faces on a letter like this? Have a good one.

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