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Thread: WHAT REAR GEAR RATIO

  1. #1
    Senior Member EXPERT BUILDER
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    WHAT REAR GEAR RATIO

    WHAT REAR GEAR RATIO BE GOOD FOR MY CAR?LOCAL TRACK IS 1/8 BUT THE OTHER TRACKS WILL BE 1/4...I'M THINKING HP RPM BE AROUND 7500RPM TO 7800RPM[I'M GUESSING]IF ANYONE CAN TELL ME THIS[RPM RANGE]WOULD BE GREAT ALSO..
    OTHER THING CAN I GET BY WITH A SET OF STREET/STRIP GEARS OR DO I NEED TO GO WITH THE PRO GEARS?
    SPECS;
    540bbc blown alcohol engine
    4.50 bore
    4.25 stroke
    6.535 rods
    11.8 static comp.
    731/726 lift roller //114 lobe center //running dur 322--326//dur at .050 284--288
    brodix 2-plus heads flowed to 372cfm on intake at 700 lift
    12-71 blower 25%OD
    big&ugly injector hat
    port nozzles
    990 pump
    fuel system flowed by spud miller

    trans;;pg with brake
    1;80 straight cut gears
    10 disc high gear

    strange spool
    35 spline strange axles
    car estimated at 2800 lbs
    32x14.5x15 slicks

  2. #2
    Senior Member RACING JUNKIE
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    Fountain,MICHIGAN
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    Re: WHAT REAR GEAR RATIO

    Quote Originally Posted by hotrodharley
    WHAT REAR GEAR RATIO BE GOOD FOR MY CAR?LOCAL TRACK IS 1/8 BUT THE OTHER TRACKS WILL BE 1/4...I'M THINKING HP RPM BE AROUND 7500RPM TO 7800RPM[I'M GUESSING]IF ANYONE CAN TELL ME THIS[RPM RANGE]WOULD BE GREAT ALSO..
    OTHER THING CAN I GET BY WITH A SET OF STREET/STRIP GEARS OR DO I NEED TO GO WITH THE PRO GEARS?
    SPECS;
    540bbc blown alcohol engine
    4.50 bore
    4.25 stroke
    6.535 rods
    11.8 static comp.
    731/726 lift roller //114 lobe center //running dur 322--326//dur at .050 284--288
    brodix 2-plus heads flowed to 372cfm on intake at 700 lift
    12-71 blower 25%OD
    big&ugly injector hat
    port nozzles
    990 pump
    fuel system flowed by spud miller

    trans;;pg with brake
    1;80 straight cut gears
    10 disc high gear

    strange spool
    35 spline strange axles
    car estimated at 2800 lbs
    32x14.5x15 slicks
    DON,
    I would go with a 4.10.
    It will work for Both 1/8 and 1/4.
    Later
    Greg

  3. #3
    Senior Member RACING JUNKIE
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    i was thinking more along the lines of a 4.30 or 4.56..... :wink:
    GOOD PARTS AREN'T CHEAP AND CHEAP PARTS ARE NEVER GOOD.........
    http://img.photobucket.com/albums/v2...lastscan-3.jpg

  4. #4
    Senior Member RACING JUNKIE
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    Gear

    Quote Originally Posted by fast75vega
    i was thinking more along the lines of a 4.30 or 4.56..... :wink:
    How MANY Times have YOU,sat behind a Blown Alcohol Motor.............?
    Later
    G 8)

  5. #5
    Senior Member RACING JUNKIE
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    Re: Gear

    Quote Originally Posted by bbchevy
    Quote Originally Posted by fast75vega
    i was thinking more along the lines of a 4.30 or 4.56..... :wink:
    How MANY Times have YOU,sat behind a Blown Alcohol Motor.............?
    Later
    G 8)
    none myself. but figure he's gonna have around 2000 hp out of that set up and will end up needing a bigger tire to put it to the ground :wink:
    GOOD PARTS AREN'T CHEAP AND CHEAP PARTS ARE NEVER GOOD.........
    http://img.photobucket.com/albums/v2...lastscan-3.jpg

  6. #6
    Senior Member RACING JUNKIE
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    This is what comes up on Wallace caculators for the qtr. mile, useing your spec and estimatining the HP to be 1200. This is without figuring in converter slippage which could be as much as 5%, i was useing 7500 RPM.

    Zip.

    1/4 Mile ET: 8.16
    1/4 Mile Top End Speed: 173.46
    Ideal Ratio: 4.12

  7. #7
    Senior Member RACING JUNKIE
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    Gear

    Quote Originally Posted by zipper06
    This is what comes up on Wallace caculators for the qtr. mile, useing your spec and estimatining the HP to be 1200. This is without figuring in converter slippage which could be as much as 5%, i was useing 7500 RPM.

    Zip.

    1/4 Mile ET: 8.16
    1/4 Mile Top End Speed: 173.46
    Ideal Ratio: 4.12
    Hi Zip!
    I had Figured about 12-1250 HP?Those Heads are KILLING that set up!!!!With the Proper Cyl.Head,and some more Stick,15-1600 is Possible......?
    Later
    G 8)

  8. #8
    Senior Member RACING JUNKIE
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    tci calculator says different 32 tire, 170mph ,8500 rpm,1:1 trans, 5% converter slip..... says 4.553

    those heads arent that bad... granted their are better one on the market but i know a few guys that run them and i bet he's flowing alot more then 375 cfm's with that combo..... just my 2 cents of course :wink:

  9. #9
    Senior Member EXPERT BUILDER
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    thanks everyone for the inputs;;please keep them coming;;on subject of heads..i sent them in to a highly recomemded machine shop that has a newer up-to-date flow bench;;they did some porting/and other stuff to heads;;not sure exactly what all was done but to give a better ideal on what was done on them..they said they had a roughly 3 stages of porting and flowing;;1st--strip &strip[weekend warrior]job[said wouldn't be even close to what i needed;;2nd--was a race only type job[for something that was going to race only and do it to win]3rd;;was for trying to get every drop of HP out of them but be on the edge of what heads would handle..
    with my other eng specs we decided on the 2nd job;;

    don't know if this helps or changes the decision on what gears or not

    when i first started this build it was going to be used mainly car shows and cruise-ins and raced now and then..have way though build i decided it was a waste sitting at car shows and wanted to use it for what i really wanted to do and that was drag race..i'd already built rearend with 4;88 street/strip richmound gears..every telling me with my engine i'd better so with pro gears..since car won't see any street and just race i'm going with the pro gears but trying to just do it[change gears]once..
    sorry for such long post but more details you have then i feel better chances of getting right answers;;
    thanks for your help
    Don

  10. #10
    Senior Member RACING JUNKIE
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    A couple things comes to mind, you're going to have to have a good set of Zoomies, 2 3/8" or 2 1/2" to push the exhaust out, collector headers won't get it done. The other thing is that you don't want to turn that motor much over 7500 RPM, with 25% over drive you'll be restripping the blower every 15 passes or less also changing the rod bearings every 15 passes or less. Glad you got Spud Miller to flow the injections, between him and Ralph Gore they are 2 of the best in the business. I've always used Ralph Gore, but have heard nothing but good things about Spud Miller. i hope you have a good tight 10" converter because the torque of that motor will blown thru anything smaller. Good luck Don and i can't wait until you make the first T&T. There's nothing in your life that will wake you up like sitting behind a Blown alky engine, Ahh!! the memories and i still have one but it's a sm/blk. I agree you may need more tire, depending on your suspension.


    Zip.


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