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What Size Tourque Converter Do I Need

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67retzke

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Discussion starter · #1 ·
I have a 509 BBC with 700 horse and 620 ft lbs of tourqe at 5000 rpm on my dyno slips thats just the engine.The motor has 10.2 compression dart pro 1 325s and has a brodix intake a solid roller cam 714-714 lift with 266- 274 duration.I shift the car at 7000 rpm.The motor is in a 80 malibu with 4.10 gears and a turbo 400 tranny w/ transbrake.The car runs 10.40s.I have a 8 inch converter and it stalls out at 5500 on the trans brake.Some people tell me i should run a 4000-4500 converter.Will this help me lower my et or does this sound right for the car.My 60 ft was 1.53 - 6.68 at 104.1 and the quarter in 10.45 at 128.9.If anyone has any good suggestions or has experienced good gains from a different tourqe converter i would like to hear it.Thanks
 
#2 ·
5500 sounds about right to me. Of course, one converter that stalls 5500, may not be as good as another. What brand is it?
 
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#3 ·
Where is your torque peak at, right there at 5K? With a motor and trans combo like you have, you'll find the best performance with stall speed right at the torque peak or barely over it. If you ran a Glide then it'd like stall speed in the 300-500 over torque peak area. That said, I'd recommend an 8" C100+ converter, like the TCI 254003 aka their 'Group 8' which should be in the 5200 area with your combo, or possibly a C150+ which would be about 200 rpm tighter. I just did a converter change along with a stiffer low gear in a pal's Firebird with a 427" SBC and between the converter and low gear change he dropped a bit over .5 in the quarter as an example of what there can be to gain in some combos if things are not optimum to begin with.
 
#4 ·
Well the first thing to check is where the converter "actually" stalls to. Everybody with a race car has a 5500 converter, but there is only one way to know for sure. Put it on the trans brake with no chip in the 2 step and put it on the floor. Watch the tach closely and see what the motor stops at. This is the true stall of the converter behind your motor. Then based on that you can make a decision. I myself agree that your stall should be a few hundred higher than the motor's peak torque. So whether you want to buy a new one or have yours adjusted, is up to you. But first make sure it's doing what it's supposed to.
 
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#5 ·
Oldani Motorsports said:
Where is your torque peak at, right there at 5K? With a motor and trans combo like you have, you'll find the best performance with stall speed right at the torque peak or barely over it. If you ran a Glide then it'd like stall speed in the 300-500 over torque peak area. That said, I'd recommend an 8" C100+ converter, like the TCI 254003 aka their 'Group 8' which should be in the 5200 area with your combo, or possibly a C150+ which would be about 200 rpm tighter. I just did a converter change along with a stiffer low gear in a pal's Firebird with a 427" SBC and between the converter and low gear change he dropped a bit over .5 in the quarter as an example of what there can be to gain in some combos if things are not optimum to begin with.
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Steve, my converter stalls 6k behind my 489 in my Camaro. Mike Munsinger tightened it up "as much as possible without changing the stator", quote from Mike. I wanted it around 55-5600, but mike said changing the stator would "make it more violent on the launch and less efficient on the top end". It cost me $250 to get it from what would have been about 6500 down to 6k. He guessed it would be 57-5800.

Would spending at least that much, probably more, to get it closer to 5500 really be worth the expense? I already ran another Munsinger 8" that went 6500 in my car and that is where the 5.97@115 and 1.36 60' run came from. It would have to pick up at least .02-.03 60' to make it worth it to me. Do you think it would make that much difference?

To make the matter more unclear, I ran a 10" Munsinger in it also, it went 1.40-1.41 60', 6.19@112 1/8th if I remember right. It would go 51-5200, but it was slow getting to that RPM.(would be great on N2O) This is why I think you are better off erring on the loose side, rather than too tight. Am I wrong about this?
Thanks!
 
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#6 ·
I'd just say call the dudes at edge torgue converters. They'll custom build you one to your application off the powerband of your cam. Take all the guess work out of it.
 
#7 ·
Davec43 said:
I'd just say call the dudes at edge torgue converters. They'll custom build you one to your application off the powerband of your cam. Take all the guess work out of it.
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I really like my EDGE converter. Call and Talk to Andre, great guy.
 
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#8 ·
It can be a tradeoff between having exactly what you need. The uncut 'C' stator as used by many will be more agressive on the torque multiplication but less efficient downtrack than the cut 'CCX' stator which gives a softer hit due to less torque multiplication but better efficiency downtrack. Remember if the converter is multiplying torque it will be more efficient and have less slippage. The trick is to get a stator that will give you enough 'hit' to leave well, yet let the motor not totally reach a point where it has torque multiplication fall off to where it's not efficient in operation. If you require less stall speed but want to retain the same stator for efficiency reasons it's a very simple fix: go up to a 9" converter from your current 8". Just the jump in core size from 8" up to 9" will drop stall speed roughly 500-700 rpm if you keep the same stator, and fin angle as you run now. I don't think you'll see huge gains, but with the engine operating where it makes more torque at you should run better all along the way. And, a converter should not be built to where a cam's supposed 'power band' is at. You need real, hard numbers on horsepower AND torque for the motor, plus you need ALL details of the car it's to be run in; trans type and gearing, rear gear, tire size, suspension, altitude you run at, etc. Too often I have guys with street or street/strip cars want to buy a converter and they're well... just a TAD optomistic with their power claims, lol. Be honest about your combo, make sure it's not a mismatched setup, and have realistic goals/ideas as to how you want to run/race it. If you can provide this to the person you get your converter from usually you'll be pleased right away. But, even then you'll find most racers will end up tweaking/testing converter combinations to find the best-performing setup!
 
#9 ·
Oldani Motorsports said:
It can be a tradeoff between having exactly what you need. The uncut 'C' stator as used by many will be more agressive on the torque multiplication but less efficient downtrack than the cut 'CCX' stator which gives a softer hit due to less torque multiplication but better efficiency downtrack. Remember if the converter is multiplying torque it will be more efficient and have less slippage. The trick is to get a stator that will give you enough 'hit' to leave well, yet let the motor not totally reach a point where it has torque multiplication fall off to where it's not efficient in operation. If you require less stall speed but want to retain the same stator for efficiency reasons it's a very simple fix: go up to a 9" converter from your current 8". Just the jump in core size from 8" up to 9" will drop stall speed roughly 500-700 rpm if you keep the same stator, and fin angle as you run now. I don't think you'll see huge gains, but with the engine operating where it makes more torque at you should run better all along the way. And, a converter should not be built to where a cam's supposed 'power band' is at. You need real, hard numbers on horsepower AND torque for the motor, plus you need ALL details of the car it's to be run in; trans type and gearing, rear gear, tire size, suspension, altitude you run at, etc. Too often I have guys with street or street/strip cars want to buy a converter and they're well... just a TAD optomistic with their power claims, lol. Be honest about your combo, make sure it's not a mismatched setup, and have realistic goals/ideas as to how you want to run/race it. If you can provide this to the person you get your converter from usually you'll be pleased right away. But, even then you'll find most racers will end up tweaking/testing converter combinations to find the best-performing setup!
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Munsinger is one of the best IMO. I trust his advice obviously or he wouldn't be getting my business. Judging from your specs, and what Mike said I would say my ATI has the "CCX" type stator. I just looked at one of my dyno sheets. I have about 20ft lbs more TQ at 5300 than at 6k. 697@5300, vs 674@6000. Not much of a difference. I am not planning on doing anything right now, but I may change next time I freshen up the engine. Thanks for your time Steve.
 
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#11 ·
THEL78ISGREAT said:
The stall on a converter changes depending on the torque the car makes. And its not stall that matters, its flash speed.
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The "car" doesn't make torque, the engine does.;) And I think just about everyone already knows the stall speed is dependant on engine TQ(among many other things). And to say it's not the stall that matters, it's flash speed makes no sense to me whatsoever. But thanks for that informative addition to this thread.:confused:
 
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#13 ·
Ok, when I talk about stall speed for my setup, I'm talking about engaging the trans brake, and hitting WOT. Which to me would be the same as "flash speed". If you don't have a trans brake, you could put the car in high gear, and hit WOT, that would give you "flash speed". Stall speed, and flash speed mean the same thing to me when talking about racing converters.
 
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#17 ·
I thought you were supposed to get a converter based on the stall speed (the rpm the engine stabilizes at when the 'brake is applied and you floor it), not the flash speed (the peak rpm that you get with the 'brake on and full throttle.)
The flash stall is higher than the actual stall.

Please correct me if I am wrong.
 
#18 ·
Flash speed is what the converter will allow the engine to instantly rev to and yes, it is higher than stall speed. If you dont have a trans brake, however, you want to get the engine t rev right into your power band from launch so you would have to select the right flash speed.
 
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