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Technical Trouble running 6v71 blower

Discussion in 'The Hokey Ass Message Board' started by William.dtA, Jun 24, 2020.

  1. William.dtA
    Joined: Dec 8, 2018
    Posts: 4

    William.dtA

    Hello. Just wondering if anyone's got an idea what the problem I'm having could be.
    I've got a 6v71 blower, fully rebuilt, sealed etc... The blower's securely mounted with all gaskets to a blower intake, all properly installed. When attempting to start the car, it runs at about 1100 rpm for a few seconds after cranking, then dies.
    I believed this to be a vacuum leak at the carbs at first, but I'm not entirely sure, just looking to see if anyone could help.
     
  2. treb11
    Joined: Jan 21, 2006
    Posts: 3,459

    treb11
    ALLIANCE MEMBER

    What engine? What displacement? What compression? What its? What cam? What Ignition system?
    Carbs? How many? What brand? What jetting?
    Fuel delivery system? Electric? Mechanical? Fuel regulator?
    Information is needed to answer your question
     
    Truckdoctor Andy likes this.
  3. If you think it's Vac then put a Vac gauge on below the butterflies and watch it while running.
     
    flatford39 likes this.
  4. 32v
    Joined: May 20, 2007
    Posts: 948

    32v
    Member
    from v.i.

    Is the blow off valve seated
     
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  5. Jmountainjr
    Joined: Dec 29, 2006
    Posts: 1,109

    Jmountainjr
    ALLIANCE MEMBER

    Who's manifold for the 6V? And you are sure it's a 6V? Homemade? The bottom of the carbs will see vacuum caused by the blower, not manifold vacuum. If you think it's a leak at the carb base, or anything above the blower mounting at the manifold, spray some fluid and see if the engine races. But to do that it needs to stay running. And a vac leak usually does not act like your description. So my guess is that you have another issue, but you have not given enough info for me to go on.
     
  6. squirrel
    Joined: Sep 23, 2004
    Posts: 46,122

    squirrel
    Member

    pictures and video really help for remote troubleshooting.
     
  7. William.dtA
    Joined: Dec 8, 2018
    Posts: 4

    William.dtA

    The 6v's on a sbf 289 with 11:1 compression mild flat tappet cam. Fully ported aluminum heads, all aluminum and forged internals, crank rods pistons.. with an off the shelf 6/71 aluminum intake, with 6v71 adapter plate bolted down and fastened securely. Its powered by an msd 6AL ignition and and an electric fuel pump.
    The cars got a single dominator 1050.

    Basically when starting the car up the idle jumps up to about 1100 and runs for a couple seconds, then shuts off. Giving it a little throttle keeps it running for a couple seconds more, but it will not come to idle, and just shuts off. It almost sounds like its leaning out like a top fuel car before it switches to nitro.

    The blower was extremely overdriven so I'm taking this into consideration.
    Thank you for the responses, and I hope this info helps give you all an idea.
     
  8. squirrel
    Joined: Sep 23, 2004
    Posts: 46,122

    squirrel
    Member

    6v71 on a 289, extremely overdriven, on an 11:1 motor? Hmm....something here does not add up.

    But it should at least keep running at idle. sounds like it's running out of fuel or spark, so you're gonna have to do some checking on things like float level, fuel pressure at the carb, etc.
     
  9. Jmountainjr
    Joined: Dec 29, 2006
    Posts: 1,109

    Jmountainjr
    ALLIANCE MEMBER

    With that much compression and a really over driven blower, are we talking gas or methanol?
     
  10. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 5,035

    Ebbsspeed
    ALLIANCE MEMBER

    That sounds like a recipe for all kinds of trouble.
     
  11. seb fontana
    Joined: Sep 1, 2005
    Posts: 6,470

    seb fontana
    Member
    from ct

    11:1 !! Holy crap thats a lot. My thought is you are running out of fuel because on first start up it runs then stops but will run longer if you open the throttle some but then stops; so you are running on whatever the accelerator pump supplies, jiggle the throttle more and it would probably run longer. So accelerator pump works but idle circuit or even main does not..So have you set the float level and have the mixer screws open a couple turns? [probably] The 1100 rpm can be brought down once it will stay running by the idle speed screw..
     
  12. VOODOO ROD & CUSTOM
    Joined: Dec 27, 2009
    Posts: 1,234

    VOODOO ROD & CUSTOM
    Member

    11:1, 6/71 overdriven and 1050 Dominator with 289 c.i.

    Count backwards from 10 and that is all it will take to start pulling the threads out of the head bolts.

    ie. blast off.

    VR&C.
     
    ottoman and harpo1313 like this.
  13. Hollywood-East
    Joined: Mar 13, 2008
    Posts: 1,197

    Hollywood-East
    Member

    KIMG7194.JPG How many Kit's of nos... Only thing missing with that recipe, I would like to see a picture of this"adapted " intake... V-671's have a 7/16 I believe size bolt running down the back of the blower to counter the load of the drive, Doe's this intake have that?
     
  14. Penetrator
    Joined: Aug 25, 2011
    Posts: 391

    Penetrator
    Member
    from SK CAN

  15. The head gaskets are already toast, the motor fires, draws a bunch of coolant into the cylinders and puts out the flame. 11:1 with an oversized, overdriven blower on an engine with 7/16" studs. The lifespan on that thing will be measured in minutes.
     
    Penetrator and Truckdoctor Andy like this.
  16. The specs on this make me go :confused:

    Is this the car/engine in question:
    "85’ Mustang- Blown Alcohol small block ford (street car)" from your profile?

    Whatever the issue, the whole deal is OT anyway.
     
  17. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,150

    gimpyshotrods
    ALLIANCE MEMBER

    Just walk away.
     
    Sky Six and squirrel like this.
  18. DDDenny
    Joined: Feb 6, 2015
    Posts: 13,445

    DDDenny
    Member
    from oregon

  19. Sky Six
    Joined: Mar 15, 2018
    Posts: 1,511

    Sky Six
    Member
    from Arizona

    I don't mean to be rude but there is a huge difference between a blower motor and a motor with a blower. Just for fun, what percentage is "extremely overdriven"?
     
    Nitroholic likes this.
  20. GasserTodd
    Joined: May 15, 2009
    Posts: 393

    GasserTodd
    Member

    As everyone ahead of me has said, thats not a motor for running, thats a motor for disassembling and rebuilding with the right parts. Now if its an alky race engine with alloy heads then you might have a chance.......

    Im no expert but I have owned a couple of streetable blown big block Chevs and these are the items I was told I needed to sort before the engine was fired up on pumpgas:
    Engine compression around 8.0:1
    Fresh rings and bearings
    Double keyway on crank
    112-114 degree separation on the cam
    Decent head gaskets (I used copper and probably should have used Cometic)
    No vacuum leaks
    Decent ignition system with heaps of spark
    Carbs set up for blower (start rich)

    Good luck, we all want you to succeed, but your engine recipe does scare me somewhat.
     

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