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Thread: what rear gear raito

  1. #1
    Senior Member EXPERT BUILDER
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    what rear gear raito

    i have 4;88 gears now and been told i'm to low gears for blower engine.my first blower engine.will be doing some controled gurge racing at car shows and cruises[at air ports NOT ON STREET]1/8th mile and some less.but also whant to do 1/4 at the drag strips..what gear raito should i run or can i leave what i have in car now?still building car so don't have rpm range on engine just the specs i have below..also trying to get converter built for car and they want rear gear raito before converter can be built..

    CAR BUILD SPECS
    540bbc/11.8 comp pistons/heads will be done by curtis[pro valve job/c-n-c ported and flowed/i think he said around 445 cc flow but don't remember if that is before or after he works on them]they are brodix 2-plus heads/roller cam with 736 lift 116 LC ;871 stage 4 blower/aly injection bird catcher w/modified square doors]mallory super maglll ign.//trans is PG with 10 disc high gear-stright cut 1;80 planitary-trans brake/4;88 rear gears/spool/32.14.5 slicks/
    62 nova wagon built into a 2 door seden delivery with glass doors/front end/guted tail gate-full chassis car with M/S cage[hope to certifie to 7;50/has steel firewall and steel floor with middle trans tunnel and drive line tunnel aluminum/christ alston a-arm front end/ladder bar rear/

  2. #2
    Senior Member RACING JUNKIE
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    If you plan on running a qtr. i think you're going to need 4.10's certainly no more than 4.30's, blower motors have a tendency to come on strong on the bottom end, unlike a turbo motor, The boost is up immediately, around 3,000 rpm. I'm going with 4.30's in my Anglia but donot intend to run anything but 1/8 mi.

    JMO

    Zip.

  3. #3
    Senior Member EXPERT BUILDER
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    not getting any smack about the right gears here.is everyone agreeing with zip?i highly respect what he says on here but odd that no one else has agree or disagree with these gears..

  4. #4
    Senior Member DYNO OPERATOR
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    I always determine my or your gear ratio based on the predicted or the actual MPH you will be running at which ever finish line you are racing to.
    If you had an automatic trans and thought you could make the power to run 161 to 164 MPH at the finish line and you had 102" roll tire and wanted to rev 7650 RPM in the lights 4.33 would be a good choice no mater what your power came from blown or sucked. If you think you have more than that then maybe 4.10 would be better. Only the power that your engine actually makes, its weight, tire roll out and RPM you are targeting at the stripe is known you will be guessing what one is perfect for you in the end. I hope this gives you some insite on your question.

  5. #5
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    Quote Originally Posted by TopspeedLowet
    I always determine my or your gear ratio based on the predicted or the actual MPH you will be running at which ever finish line you are racing to.
    If you had an automatic trans and thought you could make the power to run 161 to 164 MPH at the finish line and you had 102" roll tire and wanted to rev 7650 RPM in the lights 4.33 would be a good choice no mater what your power came from blown or sucked. If you think you have more than that then maybe 4.10 would be better. Only the power that your engine actually makes, its weight, tire roll out and RPM you are targeting at the stripe is known you will be guessing what one is perfect for you in the end. I hope this gives you some insite on your question.
    this is above my head..i don't have car or engine built yet[done i mean]i've got all engine parts but not togeather yet.so i have no ideal what speed or rpm i'll be doing across the finish line.the reason trying to find out if i need to change rear end gears or not is because when i called my converter man to build a converter he said it would make a big differance on converter build between the gears i have now[4;88] and the 4;10 and 4;33's i'm being told i should go with.i'm on disabilty so can't afford to have on built for my 4;88 and then find out later i should go with 4;10's and then would have to have another converter built.gears cheaper to change then converters.

  6. #6
    Senior Member DYNO OPERATOR
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    Welcome to the world of hot rodding. If it were easy every one would have the perfect set up every time. You will have a learning curve due to the un knowns that you don't know about your own car and combination. For some of us that is the enjoyment we get out of our sport. Sorry no crystal ball to help you with

  7. #7
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    Quote Originally Posted by TopspeedLowet
    Welcome to the world of hot rodding. If it were easy every one would have the perfect set up every time. You will have a learning curve due to the un knowns that you don't know about your own car and combination. For some of us that is the enjoyment we get out of our sport. Sorry no crystal ball to help you with
    this isn't my first car;;been building my own cars for 30+ years.i do everything myself.build eng./chassis/fab work/paint /interior/nothing gets hired out.BUT i do listen to others that has already been there or has tried something and it work or didn't work..saves a lot of money and time if you can find someone that has already tried something you are fixing to try and they tell you it didn't work then you just stop from making same mistake they did so you can apporch it another way.i'm sure there is someone out there that has close to same engine/trans/car weight as me that can tell me there best combo they found for there car was this or that.being on disabilty and building a car as a hobby i can't go out there and buy 3 or 4 sets of gears and matching converters just to find the right combo.not looking for a perfect combition first time.just a good middle area to get me togeather.not racing for a living so doesn't matter if car is a few hundreds sec. slower then if i was to spend another $1500.00 for differant gears and converter then i'd be a few hundreds sec faster.i'm building a car to have fun with not to make me homeless becaus i loose a race

  8. #8
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    Then put 3.90 gears in it and forget about it. Then you can tell your converter builder something that is known. The power and torque of your engine will be bigger players in your equasion reguardles what gear you end up with. You won't out grow the 3.90 gear untill you start running low 7 second quarter miles.

  9. #9
    Senior Member RACING JUNKIE fla1976's Avatar
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    Ratio

    I agree with TopSpeedLowET. You have to set some type of goal before you start putting it together. It's more realistic to set the goal and assemble the parts after you collect input on what will get you there. JMO

  10. #10
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    Quote Originally Posted by TopspeedLowet
    Then put 3.90 gears in it and forget about it. Then you can tell your converter builder something that is known. The power and torque of your engine will be bigger players in your equasion reguardles what gear you end up with. You won't out grow the 3.90 gear untill you start running low 7 second quarter miles.
    thanks..didn't mean to come on so strong in last reply.i have a hard time getting across what i'm trying to build.i'm putting everything into this car and want to get the most out of it.basically the easy way to explain it is i want to build a strong/easy in the 8's street legal car is all i'm going after.


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