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Thread: Running rich on a Holley

  1. #1
    Does anyone know if it normal for a Holley to run rich while at idle? I have my engine built and running and it seems to run good. I do notice that when I pull the plugs they are black with soot, evidence it is running rich. I was told this is normal for Holleys and that when I get it to the lake and open it up it will burn that off and burn normal. I just want to get this ironed out before I connect the driveshaft and head to the lake. The Holley is a 4160 and was bought new and still pretty much new. Thanks for any help on this.

  2. #2
    Do the idle jets work? Can you cut the idle down with them?

  3. #3
    Could be a blown power valve.

  4. #4
    Could be high floats or over carbed. What is the engine combo? What size carb, brand. What size jets primary-secondary? How much timing, plug heat range? Altitude and temp. ( THINGS TO THINK ABOUT.)

  5. #5
    If the carb is in good condition then start with a vacume guage! After vacume range has been established then check power valve to make sure it is proper for your application! I have been told that you need to be at least 2 inches lower on the power valve then your lowest vacume reading at an idle! Check you idle screws they should be some where around 1.25 to 1.75 turns out from fully closed. With this all proper the next thing would be to start checking jetting. I like to do primary first, which means staying out of the secondaries while tuning. When you get the primarys good then you can open the secondaries & continue there! Also recommend using a new set of plugs while doing this.

  6. #6
    Originally posted by kingb36
    Could be a blown power valve.
    Has the motor had a backfire through the carburetor?
    If it has experienced a through the carb backfire and your carb does not have power valve blowout protectection I would almost guarantee a blown power valve.
    A blown power valve can make your engine run rich at idle and you may experience erratic idle characteristics as well. (surge)

  7. #7
    Seems like everyone is pretty much pointing to the power valve. The jets are factory and came in the Holley when I bought it new. The engine is pretty much stock except for the Marine cam (nothing radical) and a bunch of life saving oiling upgrades. I have been jacking with the idle screws with a vacuum guage hooked up. What I did was I hooked the guage up while the engine was shut down. I hooked it to the large vacuum port on the aft base of the carb. I then run the idle screws out 1 1/2 turns. I then start the engine and record the vacuum. I noticed the only way that I can increase the vacuum is by screwing the screws In and not out. They are almost screwed all the way in for the highest vacuum reading. I am not sure if this is right, but thats how my carb seems to work. Also I am not sure how to change a power valve out if thats what the problem is and how to check if it is bad. Is it difficult or a simple undertaking? I ordered a book on the carb and should recieve it at Barnes Nobel tomorrow. Any ideas on all this?

  8. #8
    Tom Foolery
    Its simple. If you have any doubts get yourself a holley manual so you know what you are looking at and they will walk you through it. I rebuilt my carb last year following the manual.

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