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5,000 stall, what RPM street launch trans brake?? |
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Dan390
AMC Addicted Joined: Mar/20/2012 Location: MN Status: Offline Points: 606 |
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Posted: Mar/24/2021 at 8:48pm |
My car came with a 5,000 stall converter, has a trans brake on a TH400 and was drag raced at the track, I only street drive it though.
So my question is, when I want to have some fun and do a trans brake launch, what RPM should I go to before letting it go? Can I do less than 5,000, is that going to hurt anything? I know a lot of guys just mash the gas pedal right before green and then "go" in an actual drag race, but on the street I won't be up against a tree, just me having a good time. I know overall this is rough on a car, so I just don't want to do anything that might cause even more damage or wear than normal. Sometimes I might want to do a lesser launch or other times a full blown launch, depending on who's with me for a ride or the mood I am in. I also run a street legal drag tire (not a full slick), 4:10 gears in a 9" Ford, with Cal Trac rear suspension. What are my options to have some street fun? Thanks!
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PROSTOCKTOM
Supporter of TheAMCForum Joined: Jun/20/2010 Location: Indiana Status: Offline Points: 2427 |
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Usually it best to leave about 900-1000 rpms below the stall speed so it allows the convertor to flash.
Tom |
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Molnar Technologies Full Service Dealer - Crankshafts & Connecting Rods
1969 AMC Rambler Rouge Race Car 1974 AMC Hornet Hatchback, Wally Booth Outlaw Nostalgic Pro Stock Race Car Project |
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6768rogues
AMC Addicted Joined: Jul/03/2007 Location: United States Status: Offline Points: 6231 |
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I don’t use a that high a converter stall for the street. It will be slipping all the time in normal driving, and that creates lots of heat.
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Located usually near Rochester, NY and sometimes central FL. |
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Dan390
AMC Addicted Joined: Mar/20/2012 Location: MN Status: Offline Points: 606 |
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Normally I wouldn't either but it came this way when I bought it, I've actually only noticed slipping in 2nd gear, rarely, and at a certain speed (I forget what it was, been a long winter!), so I just speed up and go into 3rd.
For sure the car is meant more for actual drag use than street, but the former owner used to street drive it from time to time, and also to and from the track from what I understand also, it behaves very well in every respect, other than eventually I am sure things will wear sooner as a result. On the other hand, if I were drag racing all the time, things would get broken probably every weekend! Also thanks Tom for the RPM advice, I appreciate it! I'm open to any other advice too if anyone has different experience?
Edited by Dan390 - Mar/24/2021 at 10:41pm |
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mixed up
AMC Addicted Joined: Jun/16/2015 Location: Monroe mich Status: Offline Points: 2156 |
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street car with nasty habit I love them always on the jagged edge and ready for a race that for me I would run a good trans cooler for that application
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69 amx 290 auto
65 220 290 4spd 80 ford fairmont |
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XJ6
AMC Nut Joined: Jul/09/2020 Location: SW Status: Offline Points: 293 |
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More like 2 LARGE coolers...I have 2 on a 10" 3000 converter
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Ken_Parkman
AMC Addicted Joined: Jun/04/2009 Location: Ontario Status: Offline Points: 1815 |
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Full throttle on the brake is very hard on things, and generates incredible heat. All the engines power is being turned into heat, 1hp is 746 watts, so 400 hp is a 300,000 watt electric heater in the tranny! No more than a second or 2 absolute max. And it is a tremendous impact load on everything; you need the best of parts.
In normal driving the converter may really not be that bad. I know quite a number of people running good quality 8" converters on the street without much problem. I cannot stress how much difference the quality makes. If the stall has been achieved on a too large a diameter converter by screwing up the internal geometry you have a transmission melting HP eating piece of garbage. I have seen them eat 100 hp and actually burn the red dye out of the fluid. It also makes a difference in gears, weight, etc. A higher ratio requires the converter to transmit more torque, high stall and an OD is a bad idea. I've found a good converter is really not too bad, but might have some noticeable slip if you are putting some load on it say pulling up a hill in a higher gear. A brake is really a bracket racing tool, and normally does not make much performance difference. I would recommend a 2 step rev limiter so when the brake is on the engine is on the low side limiter and not pulling so hard. I found on my car a 4200rpm low side rev limiter on the brake worked well. This was with a very very good 8" converter, about 5700 stall. My car full throttle on the brake was too violent and it was slower because the stockish suspension could not deal with the impact. Not applicable on the street, but a 2 step is a great tool for controlling reaction time. You can adjust the 2 step up or down to find the sweet spot for your car.
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Dan390
AMC Addicted Joined: Mar/20/2012 Location: MN Status: Offline Points: 606 |
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Thanks again, I should have mentioned it does have (1) trans cooler.
I too love street cars that are really drag cars, I never stop smiling when we cruise it, and when we cut it loose the entire planet just goes away and life is GOOD! I'm 601hp on this car so I appreciate the tech advice, it's built extremely well, and I know street driving is hard on these set ups so I'm just trying to preserve it as long as I can.
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ajzamc360
AMC Apprentice Joined: Jun/24/2016 Location: Huron OH Status: Offline Points: 172 |
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the harder you leave, the harder it leaves.
if you can actually get it to hook on the street from 5k, thats impressive. i can't leave in either car on any surface other than a prepped strip off my brakes, without spinning i can't wind up slow in first, shift to second and then put my foot in it without spinning on the street (powerglide in both cars) and i'm not batting much more hp than you. if your playing on the street, don't put yourself on the brake for 10 seconds. get on the button, get the rpm, get off. converters are no fun to change. i can have my glide out in alone in 25 minutes, but not because i like to, but because ive gotten good at it.
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-Broke 'N' $till $pendin' Racing
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DragRacingSpirit
AMC Addicted Joined: May/27/2009 Location: Mo Status: Offline Points: 903 |
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I have run my 8" ATI Treemaster on the street alot. Never had a problem.
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Best 1/4 mile 8.99, 1/8 mile 5.71, 60 foot 1.27, no power adders
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