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383 2500 stall speed 700R4 trans, is the stall speed compatible with 3 and 3/4 stroke



You learn something new everyday. I am having my 383 built, 500hp, and the speed shop asked me to find out if my stall speed convertor is compatible with a 3 and 3/4 stroke for the motor... Sounds like a very weird question since it is just a bored out 350. The transmission shop told me of course it will, it may stall just a little bit longer. I currently have a 2500 stallspeed in my 700R4 trans. I called the speed shop and told them what they said. The machine shop replied, we just did an engine for a truck. With almost twice the horsepower as the previous engine the truck only performed mildly better... I swapped out the stall speed, for one compatible with the 3 and 3/4 stroke motor and picked up just over 2 full seconds... So, I called the makers of the stall speed I currently have in my car, Midwest Convertors. They told me right off, that you can have two stall speeds, both 2500 rpm, one in a car with 500hp, one in a car with 250hp, and the 250hp might beat the 500hp if the 500hp car doesn't have a convertor that is compatible with that stroke... I never heard of this. He said that it can make this powerful engine perform like a dog. Wow. I figured, both are 2500, how can it make a difference? So, for you all with a 383 out there, and a 700R4, you might wanna find out if your convertor is compatible with your stroke. You may not be anywhere as fast as you should be...
thats a new one on me, I always thought the stall speed was dependent on torque for the specific converter ie. a 11 inch converter on a low hp small block might stall at 2200 while on a big block it would be closer to 2500, but then I have only done one auto and I gave the converter guy my specs and money and he sent me a converter :L
Bossvette is rite on the money in his description of stallspeed!!!! If your converter(that you now have) gave you a stall speed of 2500 with a 350cu. in.engine, that same converter behind a 383 (if all you change is cu. in.) IE.same cam,heads,fuel inj.trans.,rear gear,etc. Will give you just a slight increase in stall speed! By the way,a 383 is NOT just a bored out 350.It is a 350 bored .030 AND stroked from a stock stroke of 3.48 in. to a stroke of 3.75 in. One thing to remember is , you want to have MAX. engine torque 2-500RPMs BELOW the rated stall speed!!!!!!! :w
Well... I agreeded with his description of a stallspeed too, until I talked to the speed shop, AND the manufacturer. Two units that have the same stall speed rating, one compatible to a 3 and 3/4 stroke, the other not, will perform a difference of night and day. Midwest Cornvertors 1-800-554-2668 Weird.
Stall speed is not dependant on stroke. The stall speed should be related to the powerband of the engine, such as drags1998 recommends. While your bore/stroke ratio has an effect on the powerband, so do numerous other things, including cam, heads, intake, etc. The torque converter should be chosen to complement the whole engine package.

The stall speed rating of the troque converter is a guide, and actual stall speed will depend on a number of factors, including the engine, but also including the transmission, differential, and the brakes.

most simple falesafe rule of stall speed is to pick one that locks up when your motor comes onto cam. by that, if you dyno a motor on an engine dyno look to the point where the volumetric eff starts climbing to 95%, that is when your on cam and the motor starts pulling hard. cams effect stall more than any other engine part. your "speed shop" should know what the torque curve looks like and recomend a good converter for you, if not i would be a little leary of the work. best of luck to you, and if you post your combo we can give you a better idea of what you should be looking for. Brian

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