Convertor stall speed

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by Neil Morley, Sep 12, 2017.

  1. Neil Morley

    Neil Morley Member

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    Hey in your guys opinion what do you think would be the optimal flash or stall speed coming off the transbrake? My combination is a conventional headed BBC with a 14/71 HH retro roots, it's a 555 ci deal with a 385 cc intake runner, cam specs are as follows lift int..820" exh. .810" due.@.050 int. 280 exh. 290 with a 114 LSA. The blower @ 39% od will make 39 lbs @8000rpm , it's a heavy car 3800+ lbs with driver , it's a glide with a 1.80 first and a 4.56 rear gear and a 33" tall tire , I know a three speed would probably be better since I'm loosing 1,800 rpm on the shift but I think a looser convertor will help with that too since mine is only flashing to 4600 rpm of the two step, I'm thinking it needs to flash somewhere around 6.500 rpm, what do you guys think??? Thanks for your input.
     
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  2. Mike Canter

    Mike Canter Top Dragster

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    Since your car is so heavy and the first gear ratio I think it would help to flash up to 6000-6500. You also need to adjust the stator so you only get around a 800 rpm drop on the shift.
     
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  3. Bjs344

    Bjs344 Member

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    Similar motor in a dragster, I struggled to get a converter to flash over 6000. Finally have a setup that will go 6500 off the brake and 7000-7200 on fallback. Huge improvement. Allowed me to be .05 better to 60'

    Abruzzi seems to have this combo figured out, although I'm not sure if he has one in a car quite that heavy.
     
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  4. Neil Morley

    Neil Morley Member

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    Hello bjs344 , did it help your overall ET and did it hurt your mph after you loosened up your convertor?
     
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  5. Bjs344

    Bjs344 Member

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    Hard to make a direct comparison. In this case, I changed my power management to get the motor up.

    The difference between driving out against the converter at 6000 and jumping on the tire and letting the motor accelerate from 6500 was probably a tenth 1/8 mile, which was mostly 60'.

    This converter couples as good as any out there. I don't have driveshaft data, but 8100 rpm, 220 mph with a 3.90 gear and the little Mickey tire, I bet it's 1:1, could even be in overdrive.

    The last converter I ran before this one was 8400 going 212, but had similar flash and fallback rpms.
     
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  6. Neil Morley

    Neil Morley Member

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    Who's convertor we're you running before? And who's now? And exactly what size and model?
     
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  7. Bjs344

    Bjs344 Member

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    I started with an old JW that was too aggressive. Marco tried to adjust it a couple times before it started coming apart and he built me a new one. The new one was too loose because he was trying to bandaid my tuneup that was lazy down low. This time he nailed it. I think they have all been the metric GM case, 258 mm or something like that.
     
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