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Thread: what gear ratio for 1/8 mile

  1. #1
    Senior Member RACING JUNKIE
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    what gear ratio for 1/8 mile

    Suggestoins please 9" rear
    car weighs 3200lbs 496 bbc cam operating range is to 7500rpm TH400
    Was running 4.88s on 28" tire trapping 98 mph at about 6-6300 rpm
    recently tubbed car and running a 33"tire now would like to keep revs under 7000 since I'm just bracket racing Would 5.83s be too much?
    My math brought me to a 5.5-6.0 gear.Just sounds like alot to me
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  2. #2
    Senior Member DYNO TECH
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    Do you only want to run 1/8 or would you like to do 1/4 also?
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  3. #3
    Senior Member RACING JUNKIE mytmouz's Avatar
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    I was running a 29.5 tire with 5:14's in the 1/8. On motor only, it needed more.
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  4. #4
    Senior Member RACING JUNKIE
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    1/8 BLITTLE I MIGHT SETUP ANOTHER CENTER FOR 1/4 LATER AND SWAP AROUND
    "The problem with quotes on the Internet is that you cannot confirm their validity"- Abraham Lincoln

  5. #5

  6. #6
    Senior Member RACING JUNKIE
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    VERY COOL .THANKS A HEAP TOD74.YOU DA MAN!
    "The problem with quotes on the Internet is that you cannot confirm their validity"- Abraham Lincoln

  7. #7
    Senior Member RACING JUNKIE
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    actually that wasn't the one I intended to post. I will see if I can find it. You can google " gear ratio calculater" and find various ones.

  8. #8
    Senior Member EXPERT BUILDER
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    Olds 48, some of the problems I see with trying to gear that high a gear number is that you may have problems with traction at the start, depending on the converter you use.
    Also these high number gears are a little weaker than their lower number counterparts, due to the smaller diameter pinion gear, less teeth on the gear to spread the load.

    In my opinion it is always better to find the best gear, convertter, tire and suspension settings to get your best 60' and not be so concerned about what rpm the car crosses the 1/8 at.
    Crossing the line at the 1/4 mile is more of a concern as, by that time air resistance is slowing down the acceleration plus you dont want the motor to run out of breath before the finish line.

    With a healthy torky motor like it seems you have , and running a th400, you may have traction issues running 5.83s, even with the 33 tires.
    These types of gear ratios were used back in the days of modified production type racing, heavy 3600 lb camaros with motors less than 283 cids, and 4-speed trannys, just to help get the car moving.
    These cars were something to see, and hearing those small blocks singing at 10000+ rpm at the line was something ....
    Ed

  9. #9
    Senior Member RACING JUNKIE
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    You know,I always figured a real low gear would cause traction problems,but it seems the opposite to me.Whan I was street driving my Olds everyday I was running 3.73s and couldn't hook up at all,or get into third in the 1/8.When I went to 4.88s I started hooking immediately,with no other changes to the car.Kinda like how granny gear helps a dump truck quit from spinning,I guess?Whereas my Impala has 2.73s and once it starts spinning,it'll go forever.
    "The problem with quotes on the Internet is that you cannot confirm their validity"- Abraham Lincoln

  10. #10
    If you play around with Pages 2 and 3 of:

    http://home.earthlink.net/~whshope

    and use a realistic value for rear wheel horsepower, I think you'll have your answer.


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