Page 1 of 3 123 LastLast
Results 1 to 10 of 28

Thread: GEAR ?

  1. #1
    Senior Member SENIOR BUILDER
    Join Date
    May 2008
    Location
    east tn
    Posts
    114

    GEAR ?

    dragster weighs about 1700 33.5 tires motor about 600hp,406,,60'120,finish 550 its not coming out of the hole real strong,it has a 433 gear in it now,,im leaving the line at 4800 and shifting gears at 6800,,i think i'm crossing the finish line at around 6200 not 100 %,,,? WHAT GEAR DO I NEED 456,488,,,,thanks steve

  2. #2
    Senior Member DYNO OPERATOR
    Join Date
    Apr 2008
    Posts
    504
    If ultimate performance is your goal, I would shift 5% over the RPM that peak horsepower was measured at on the dyno. The trap rpm should also be at least 5% over the peak horsepower rpm. I have to guess what your speed is based on the rpm you gave of 6200 and tire diameter 33.5 gives me a speed of 135 MPH currently at 6200 rpm. If you put 4.88 gears in it you will be at 6939 RPM going 135. If your guess on rpm in the traps is off and you go faster then the error is in your favor to get higher rpm's in the traps. I hope this gives you some info to decide what gear to use. 4.88's are going the right way unless your rpm guess is way off. Remember that this mechanical advantage will make you ET quicker and probably faster too so any increase in the MPH will make the rpm higher in the traps as well.
    Bruce

  3. #3
    Senior Member SENIOR BUILDER
    Join Date
    May 2008
    Location
    east tn
    Posts
    114
    i am guessing at what rpm is at the finish line,i tried looking but it small and don't have much time lol,my speed is 125 right now,,the dragster comes out kinda lazy and then about the time it hits second gear its like a rocket,my 60' is only 1.20 and 5.50 overall,,played with the timing a little,,not real sure there either,but 38 may be the best spot for it,,motor is great,sounds runs good,burn out real good,just needs help getting out of the hole,,,,thanks steve


    p.s-i think there want be a big difference in the 456 gear,,433 and 456 is not much differences

  4. #4
    Senior Member RACING JUNKIE
    Join Date
    May 2003
    Location
    Coldwater, MI
    Posts
    2,998
    How high you want to zing the motor ?

    What brand of conv and is it a sprag or spragless ?
    David Lanning
    IHRA NHRA 387B

    Fleenor Racing Transmission
    419-280-1406
    Lanning Electric
    Complete Drag Car Wiring
    APD Race Engines
    www.apdracing.com

  5. #5
    Senior Member SENIOR BUILDER
    Join Date
    May 2008
    Location
    east tn
    Posts
    114
    Quote Originally Posted by hammertime
    How high you want to zing the motor ?

    What brand of conv and is it a sprag or spragless ?

    ptc 5800 converter,not sure if sprag or not,,,,6800 would be just about it on the motor,,thanks steve

  6. #6
    Senior Member RACING JUNKIE
    Join Date
    May 2003
    Location
    Coldwater, MI
    Posts
    2,998
    Quote Originally Posted by vega34
    Quote Originally Posted by hammertime
    How high you want to zing the motor ?

    What brand of conv and is it a sprag or spragless ?

    ptc 5800 converter,not sure if sprag or not,,,,6800 would be just about it on the motor,,thanks steve
    Do you know what the stall flash is and the recovery after shift ?

    I think 4:88 is to much, I used to run a 355 sbc that'd go 5.40s with a 4:10 gear and 60ft 1.15-6 no issue, took me 3 converter changes to get there though.
    David Lanning
    IHRA NHRA 387B

    Fleenor Racing Transmission
    419-280-1406
    Lanning Electric
    Complete Drag Car Wiring
    APD Race Engines
    www.apdracing.com

  7. #7
    Senior Member SENIOR BUILDER
    Join Date
    May 2008
    Location
    east tn
    Posts
    114
    Quote Originally Posted by hammertime
    Quote Originally Posted by vega34
    Quote Originally Posted by hammertime
    How high you want to zing the motor ?

    What brand of conv and is it a sprag or spragless ?

    ptc 5800 converter,not sure if sprag or not,,,,6800 would be just about it on the motor,,thanks steve
    Do you know what the stall flash is and the recovery after shift ?

    I think 4:88 is to much, I used to run a 355 sbc that'd go 5.40s with a 4:10 gear and 60ft 1.15-6 no issue, took me 3 converter changes to get there though.



    the guy who built my trans and converter says its not the trans or converter,go figure,,everyone else says it is not my motor,,so the guy that built my trans has a 456 gear that was only run one week at pinks,so i'm buying it for $150 and trying it,,i'm still saying it could be a tight converter,,,steve

  8. #8
    Senior Member RACING JUNKIE
    Join Date
    May 2003
    Location
    Coldwater, MI
    Posts
    2,998
    Quote Originally Posted by vega34
    Quote Originally Posted by hammertime
    Quote Originally Posted by vega34
    Quote Originally Posted by hammertime
    How high you want to zing the motor ?

    What brand of conv and is it a sprag or spragless ?

    ptc 5800 converter,not sure if sprag or not,,,,6800 would be just about it on the motor,,thanks steve
    Do you know what the stall flash is and the recovery after shift ?

    I think 4:88 is to much, I used to run a 355 sbc that'd go 5.40s with a 4:10 gear and 60ft 1.15-6 no issue, took me 3 converter changes to get there though.



    the guy who built my trans and converter says its not the trans or converter,go figure,,everyone else says it is not my motor,,so the guy that built my trans has a 456 gear that was only run one week at pinks,so i'm buying it for $150 and trying it,,i'm still saying it could be a tight converter,,,steve
    I also agree on a tight converter You knew my thoughts already,
    Example, 5400 stall flash way tight on mine 1.130 60ft, 5900 still tight but 1.065 60ft makes a huge difference. Remember you can tune some 60ft into it with the 4 link.
    David Lanning
    IHRA NHRA 387B

    Fleenor Racing Transmission
    419-280-1406
    Lanning Electric
    Complete Drag Car Wiring
    APD Race Engines
    www.apdracing.com

  9. #9
    Senior Member SENIOR BUILDER
    Join Date
    May 2008
    Location
    east tn
    Posts
    114
    i'm going to put the 456 in it and give it a try before checking into the converter,,,i believe the converter is tight but he don't want to think so,,,it is a 5800 ptc,,i'm going to flash it on my car and see what it will flash,,he thinks my motor is weak and not making enough horsepower,i don't think so

    my motor is a 400 30 over flat top pistons,670 something roller cam,eagle rods,eagle standard stroke crank(cast)brodix heads after all the angle milling and pocket porting there about 240 plus cc w/208 valves,100%new bearings(rod,main,cam,all new gaskets,brand new engine,,i'm thinking a 406 with about 600 hp,,,what you think,,its not my motor,,,,steve

  10. #10
    Senior Member DYNO OPERATOR
    Join Date
    Apr 2008
    Posts
    504
    I was done with this string after giving my earlier advice on gear but since you guys brought up the converter possibility this is what the numbers tell me. You have 33.5 tires if that is correct then the roll out is 105.24", next you have 4.33 gear ratio. You said that you are running 125 MPH at the stripe and guessed your rpm at 6200. If your converter had little slip like mine does at 4.75% or less, then the rpm WILL BE 5701 with these variables given at 125 MPH unless there is a denominator that is incorrect in the question. If you saw 6200 rpm that would be a bad sign for the converter for sure, not an opinion. If your stator was bad and I have had one bad right from new, which made the diagnosis challenging to say the least, My car drove off the starting line like a turtle then acted like it hit the bottle 50' out. This is sort of what you were describing at first. But the 6200 rpm does not wash no matter what, and by a lot. A 31 inch tall tire with a roll out of 100" will only net you 6000 RPM at 125 mph with a good converter slip ratio so I am saying that you know what tires you have, but the converter has to be south in a big way to give the high rpm you report at the stripe based on the MPH . I gave my gear ratio advice on my guess of 135 mph based on the info you were giving at that time exempting your MPH. It's NOT tight, its just about falling apart LOOSE ! and probably with a bad stator to boot.
    I would mull it over a bit before the gear change..........
    Bruce


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Copyright © 2005-2016 RacingJunk.com All Rights Reserved.

Designated trademarks and brands are the property of their respective owners. Use of this Web site constitutes acceptance of the RacingJunk.com
Terms of Use, Classifieds Disclaimer, Privacy Policy, and Cookie Policy