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Thread: Timing on 620" BBC

  1. #1

    Timing on 620" BBC

    Where would you run your timing on a 14.8-1 620" BBC and be safe.It is carburated on gas and n/a.Thanks

  2. #2
    Senior Member MASTER BUILDER
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    timing

    I ll get the ball rolling for the other guys to chime in, What head are You running, I hear the ones with the smaller chambers use less timing,Anyone? I run 37 now on a 572 conventional head.

  3. #3

    head

    I have the Pro1 355 cnc heads.119cc chambers.

  4. #4
    Administrator RACING JUNKIE bjuice's Avatar
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    i have a 632 with 14 degree big chief heads on gas...it likes 34.

    as they say start off conservative and work up...i will go out on a limb and say 32 would be a ( extra) safe place to start and go from there if it were mine and no dyno records to show sweet spot with timing

    Brian
    Bjuice..

    "I'M YOUR HUCKLEBERRY ! "

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    Senior Member RACING JUNKIE
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    I used to put my gas motors around 39-40, on the dyno last year my motor shop at the time started at 32. I sat back and just watched sure enough it made more hp at 34 then at 39. Every motor is different
    David Lanning
    IHRA NHRA 387B

    Fleenor Racing Transmission
    419-280-1406
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    APD Race Engines
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  6. #6
    I'm at 36 on alky

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    Senior Member MASTER BUILDER
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    Re: Timing on 620" BBC

    Quote Originally Posted by lmchevy
    Where would you run your timing on a 14.8-1 620" BBC and be safe.It is carburated on gas and n/a.Thanks
    My engine that has 355 heads on it likes 38. Is there a engine dyno you can take it to and find out what it likes?

  8. #8

    timing

    Tcarda i probably could go and put it on a chassis dyno.

  9. #9
    Administrator RACING JUNKIE bjuice's Avatar
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    Re: timing

    Quote Originally Posted by lmchevy
    Tcarda i probably could go and put it on a chassis dyno.
    chassis dyno probably would not tell you what your looking for since there is no telling how much HP is being lost thru the chassis.
    my advise is save your time and money on the chassis dyno for this purpose.


    Brian
    Bjuice..

    "I'M YOUR HUCKLEBERRY ! "

  10. #10
    Senior Member RACING JUNKIE
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    Re: timing

    Quote Originally Posted by bjuice
    Quote Originally Posted by lmchevy
    Tcarda i probably could go and put it on a chassis dyno.
    chassis dyno probably would not tell you what your looking for since there is no telling how much HP is being lost thru the chassis.
    my advise is save your time and money on the chassis dyno for this purpose.


    Brian
    That's a good point but I have a question.
    Wouldn't the chasis dyno still allow you to see a gain or a loss from a timing adjustment? I mean, regardless of what it is making at the crankshaft, if it is showing say 500 hp 400 ft lbs on the chasis dyno, and you advance the timing 1 or two degrees, then run it again, take a reading,then retard it and run it again..take another reading...wouldn't this allow you to find the timing that makes the most power?
    Regardless if the hp numbers are bogus...as long as they are consistantly bogus...wouldn't that allow you to find the tune up?
    Not arguing here...just asking.

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