need help with my Holley 850

Discussion in 'Holley' started by pitfield, Jul 27, 2015.

  1. pitfield

    pitfield Active Member

    I need someone to help me with a quick setup to get my car up and running good. I have it running but I am blowing small puffs of white smoke up through the carb and also have some gas leaking into the exhaust and popping at idle. I am not to familar with holley carbs yet and I am looking for someone to tell me a good setup to start at. Its a Holley 4150 850cfm vac sec. no choke. As of now it has 72 in the fronts 78 in the rear, and I cannot recall the power valves or the quirter size. I have 8* mechanical advance and im not sure on my total because when I hook up my vacuum advance it runs poorly. Which will be another issue I have to address. Thanks for any help
     
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Maybe you mean you have 8* initial advance? If the mechanical advance is all in early and you add in too much vacuum advance, the engine will frequently surge. Have a look here,

    http://www.v8buick.com/showthread.php?63475-Power-Timing-your-Buick-V8

    I have not heard anything good about Holley Vacuum Secondary carburetors. The 850 DP is an excellent carburetor for a BBB.
     
  3. pitfield

    pitfield Active Member

    Yes sorry initial advance. I do have a 750 dp I could try instead. Do you have any recommendations for jet sizes and squirter size?
     
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    I would start with stock and go from there. It isn't always necessary to change carburetor calibrations.
     
  5. sailbrd

    sailbrd Well-Known Member

    90% of carburetor problems are not the carburetor.
     
  6. hugger

    hugger Well-Known Member

    I would ditch the Vac Secondary myself and run the 750 it will be fine up to around 475/500hp. As Larry said set it up to stock specs, NEW HI flow needle and seats , check to make sure metering blocks are correct for the List number carb , clean very thorough, especially make certain the idle and hi speed ports are clean, then set idle mix screws out 1 turn from seated , to get it started you may want to put a few turns on the idle speed screw. Once it fires off let it warm to about 165 then you can adjust timing AND Carb together the goal is to get it to idle with little or sometimes even no turns on the idle speed screw. This is done by more initial advance and adjustment of the idle mix screws. Also b4 doubg the above put some fresh plugs in it. Mist problems with Holleys are needle and seat related or mix matched components. Then once it starts, idles , stops and turns without stalling, then you can mess squirter size , pump cams jets etc
     
  7. DEADMANSCURVE

    DEADMANSCURVE my first word : truck

    carb part numbers ? top left choke tower area . list # ------ .
    > #4779 - 750 DP
    4 corner idle , power valve = 65 , primary shooter nozzle = 28 , secondary shooter = 31 , primary jet = 70 or 71 , secondary jet = 80
    > the 850 vac might be a #80531 I think
    front idle screws only , primary jet = 78 , secondary jet = 82 , shooter = 40 , primary power valve = 45 , secondary power valve = 35 , vac secondary spring = pink .
    > those specs are out of holley book . both carbs : float level is a little dif for dif float materials but with bowl upside down and adjusting float so top of float is level with top of bowl will get ya close then adjust after running so that gas just touches threads bottom of site plug - idle up if needed to smooth out engine motion . idle screws : all in then turn out approx. 1.5 full turns ( 3 half turns ) . before start up can add approx. 2 oz (?) of gas into bowls down vent tubes ( CAREFULLY ) to eliminate dry start . if apart carb spray and fully blow out passages in metering blocks and 8 air bleeds in top of carb . blow both directions . watch your eyes . and check fuel pressure , .5-6.5 ok , 7 max .
     
    Last edited: Jul 28, 2015
  8. pitfield

    pitfield Active Member

    thanks for the advice, i changed out the front jets to 72 and the rears to 80 and the front has a 65 power valave. Squirters are stock. after fixing a minor leak it wouldent start or even attempt to start. Looks like Ill have to look into my ignition once again. Cant seem to keep anything running in this car. Thanks again everyone
     
  9. DEADMANSCURVE

    DEADMANSCURVE my first word : truck

    carb part # ? car/motor specs n info ?
    and did you buy that new or used ? if used it would be strictly 50/50 that all is stock . everybody is a "holley expert" . me , no .
    and if you can round up a known decent runnin carb ( 600 , 750 whatever - edelbrock , holley - something that'll bolt up quick ) throw it on and confirm problem .
     

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