Converters for High Horsepower Heavy Cars

Discussion in 'Race 400/430/455' started by Keith Smith, Feb 10, 2007.

  1. BQUICK

    BQUICK Well-Known Member

    I like the tight 8 in from ATI. 4200 stall in 3700 lb GS running low 10s. Auto valve body. 1-2 shifts automatically (5500), 2-3 done manually at 6500.
    Locks up nice, nice rpm drop on shifts. High 1.30/low 1.40s 60 ft with 3.73 gear.

    Bruce
     
  2. Mark Dalquist

    Mark Dalquist Well-Known Member

    4650 lbs, 11.662@ 116.11 mph. 92 octane pump gas stage-1. Custom COAN 258mm converter 4000 stall. Converter has exceptional torque multiplication. I usually talk to Art or Jason (Jason Coan) and they have always given me good pieces for various cars. My car picked up over .2 seconds with the new converter even after it slowed to 1.69-1.74 60ft times due to some initial wheelspin that I haven't worked out yet.

    I run a Coan 9" converter in a Big Chev powered Firebird drag car that I built an all iron 454 for (1969 closed chamber rec. iron heads) it has run a best of 9.248 @ 149 mph which was an improvement of .16 seconds over the previous BTP converter. It runs consistant 1.28 60ft times.
     
  3. paul c

    paul c Well-Known Member

    i used an ati in my camaro(sorry), great customer service. i had dealt with chris esterly. converter was great and they are out of baltimore.
     
  4. Keith Smith

    Keith Smith Well-Known Member

    I have always believed that you set up your converter to flash to peak torque to get the car moving. Perusing over the spec sheets from several well known converter vendors, they ask me where I want to set up the flash. What are your opinions on this? Peak torque, just below? My 10 inch is very loose and spinning to 7000 through the lights. It is actually flashing to about 600 rpm OVER peak torque now even thou the torque curve is pretty flat.
     
  5. GS Kubisch

    GS Kubisch THE "CUT-UP" BUICK

    Hey Keith,
    Congrat's on the 9 second pass,It's good to hear you've been running the car again.
    Your car is an inspiration to any Buick Enthusiast,Very nice and diceptively FAST.

    What gear and tire size put you at 7000?
    With 4.10's and 94" circumference slicks I see 7000 in good air on the faster passes.

    I'm thinking your converter is pretty close and you might go through a number of others to find and noticable improvement.
    The weight of your car is going to work the converter and challenge any company to get one "right".
     
  6. Rodney Byrd

    Rodney Byrd Torque

    That's who we use at our shop: PTC. They are one of the few places that realize a BB Buick, MoPar or Pontiac are NOT a Chevy. They tailor the stator and other factors inside the unit to deal with, and take advantage of, the low-end torque these motors make. We have used them in everything from 5.0 Mutangs right up to Pontiac chassis cars with two stages of nitrous. Our BB Buick rail, "Black Widow" even uses a 10" 3500stall PTC unit, with good sucess. I deal with Layne Crowell there, #256-383-6868... RB
     
  7. Keith Smith

    Keith Smith Well-Known Member

    Nice to hear from you Gary. Drivetrain wise the car is in the same trim as it was in 97 except quieter, I put some real mufflers on the car which added some weight and worked on the suspension. Its not complete but better. The rear gear is a 3.73 and the tires are 28.5" tall, the rollout is 90". Running through the lights at 133+ slippage seems high to me.
     
  8. rmstg2

    rmstg2 Gold Level Contributor

    Interesting thread but I have been away from racing for about 16 years so things have changed and I need a little schooling. What I'm getting out of this is there are converter mfg out there now who design a converter for the customer that will stall at the desired rpm according tp the customers engines torque rating? I realize that in the past you could buy a converter rated
    @ 4000 but your engine might not have the suds to spin to 4000 with that particular converter. Are there any other factors like less slippage under normal driving or are these race only applications. When I was doing it the
    S/P was the way to go. Sorry if I interupted this thread with my questions but old minds need to know.:laugh:
    Bob H.
     
  9. rh455

    rh455 Well-Known Member

    Keith
    Did you ever consider having yours tuned or freshened?
     
  10. GS Kubisch

    GS Kubisch THE "CUT-UP" BUICK

    Yeah Keith,That's almost 17%.
    I would say it could be more efficient but it make take a few tries.
    Happy New Year.
     
  11. Keith Smith

    Keith Smith Well-Known Member

    Gary, Happy New Years to you as well. I came up with close to the same slippage rate assuming no tire growth.
    Reynold, a tune up is only $200 if nothing is broke and I have considered it. A cheap fix but I would like to gain everything I can with the converter. Not running a class where I am restricted by converter size anymore I would like to use the best possible unit for efficiency whether it's a 8, 9 or 10" now. I am sending off dyno results and spec sheets to several of the recommended converter companies in this thread to get there input.
    A couple of questions

    1) What kind of converter slippage do you guys see assuming our tachs are accurate?
    2) Are your converters set up at peak torque or higher or lower?
     
  12. GS Kubisch

    GS Kubisch THE "CUT-UP" BUICK

    Using the same calculator mine shows 8.6% but it is a bit tight on the starting line in my opinion.
    My 9" ATI only flashes to about 4400,I'd like to see closer to 5200.
    Just haven't gotten around to spending the money to get a new one and I don't want to change the one I have as it is too "close" to mess with.
    I think the converter company will be able to say what works best,Don't think you want to be below peak torque,At or above would be my guess.

    PS
    Did you get to drive on the 9.98 pass?
    What was the 60ft?
     
  13. Keith Smith

    Keith Smith Well-Known Member

    Mine is now flashing to 6000 and peak torque is at 5400. I would prefer to be around 5200 but will let the experts influence me. The converter was never designed for this motor. It was set up for my old Stage 1 motor that ran 10.70's, I just never upgraded when I went to the Stage 2. The 60ft was a 1.42 as is pretty typical. Charlie was in the car again.
     
  14. GS Kubisch

    GS Kubisch THE "CUT-UP" BUICK

    Yes,I would say you're "driving through" the converter.
    Should be some ET gained when you get the right unit in there.
    Keep us updated:TU:
     
  15. rmstg2

    rmstg2 Gold Level Contributor

    I could have sworn one of you experts on here could have answered my question. Guess not. Well thanks anyway.:moonu:
    Bob H.
     
  16. BQUICK

    BQUICK Well-Known Member

    Keith:
    I run the tightest 8in that ATI makes. Flashes to 4200 from 2000 at the line.

    Ran 10.18 at 130 at Cecil this fall. 71 GS Stage 2, TA 608B HYD, 3700lbs, 3.73 rear, 28.5 tires

    When first built it ran 9.97 at 131 with 4.10 and 29.5 tires......but that was 6 yrs ago and the motor has close to 600 passes.
    Probably go quicker with more stall but might not be as consistant......

    Bruce
    BQUICK
    JAGUICK
     
  17. Keith Smith

    Keith Smith Well-Known Member

    Bruce,
    Did you dyno the motor to set up the converter at peak torque? It will be interesting to get back feedback from PTC, ATI, COAN and the others mentioned in this thread as I am providing them all with the same spec's and dyno sheet. You would think they would all operate under the same theory.
    Keith
     
  18. Tom Rix

    Tom Rix Well-Known Member

    Keith,

    My thoughts on the higher HP 455's like yours is that you want the flash stall about 3-500 rpm over peak torque not at or below. Our engines make enough torque to get moving well, what you want to get to as quickly as possibly is the peak HP curve. I leave off the 2-step at 2500 rpm, flashes to 5700, shift at 67-6800 rpm, drops to 5800 on shifts and goes through the lights at 7000 rpm. 1.27 60', 138 mph, 30"x9 radial tire, 4.10 gear. If you are reading a recall on the tach you are probably reading 200 rpm too high because you don't let off till slightly after the finish line. I read my rpm off the MSD data recorder right at 1320'.
    I run the tightest 8" ATI convertor they make (used 3, tightening each time).

    Good luck,
    Tom

    PS/Gary There's .2 waiting for you in tires and convertor!
     
  19. Keith Smith

    Keith Smith Well-Known Member

    Tom,
    Thats great information, thanks.. So then what I am understanding, my converter is probably flashing to an appropriate rpm but slipping too much on the big end assuming my tach is accurate - 133 mph - 90" rollout - 3.73 gear and going through at 7000. What should it be going through the lights at?
    Thanks, Keith
     
  20. Tom Rix

    Tom Rix Well-Known Member

    Keith,

    I agree with Gary that you have about 17% slip and I'm using 91" rollout because a bias ply will grow at least 1" if not more. At your weight and HP I would use a 3.90 gear, 94" radial, convertor flash to 5700 and go through traps at 6500 rpm at 135+ mph. About 11-11.5% slip which is very good in NA heavy car trying to go the quickest et possible.The lower rear gear will lower flash stall and improve convertor efficiency, a 4.10 will help even more as would a low gear set in trans.
    If you want to PM your dyno numbers (TQ & HP) from 5000-7000 rpm and I can give you better advice based on my experience. Or get better advice from ATI, Coan or PTC.

    Tom
     

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