OK, let me expound. I understand the stall convertor as explained to the masses. What I wanna know is the theory behind matching a stall convertor to a CID and weight of a car. I have always been under the assumption that more is better. But is that really true for a car like the Fly? It is 276 CID and 1880 lbs running a glide. I also have a 5.13 gear under it. Thanks
not a pro on this subject but the few convertors I have used with a higher stall was for the purpose of getting the rpms up to the bottom side of the rpm range that my motor was built to perform at with out roll'n thruogh the lights,witch made for good launches and the motor was already in its power band.more is not always better,to much is worse than not enough,as far as I could tell by e.t's like I said not an expert in this though
The stall is not really about what size the car is.... It is more about what the idle speed, and how much you want to rev the motor before you start to move... If you have a street driver, you will want a low stall, and a drag racer will want a high stall.... If your motor idles at 1000rpm, then on a street car, you will want one with about a 1200-1500 stall.... That way, when the light turns green, you just have to step on the pedal a little to get moving..... The drag race guys use the high (3000-4000,etc.) converters because their motors don't start making serious power untill those rpm's... As far as I am concerned, you should only have to rev the motor about 300-400 rpm fromidle to move... if your car needs something like 1000 rpm to start moving, then you need a lower stall... As far as weight of the car is concerned, if there is a choice in converter size (physical dimension) get the biggest diameter you can. The smaller ones are mostly for racers, to reduce the rotating mass, and allow them to rev faster...... Another thing to lok at... Get in someone's hot rod, and start it up.... now put it in drive, and step on the brake.... if you have to really stomp on the pedal to keep the car from moving at idle, then they have too low a stall in their car... Even with the right size converter for your car, there will still be a little creep at idle, but it should be a verry slow creep... So basically, if it is a street car, figure out about where it should idle, and add 200-500, and that is the stall you need.... If it is a racer, take the motor to the dyno, and figure out where the power band starts, and that is your stall.... Hope this helps a little.....
http://www.tciauto.com/tech_info/torque_converters_explained.htm there is some good, basic info here. If you are in the market of a new converter... I suggest talking right to a manufacturer (B&M, Coan, TCI etc) to make sure you get the right one.
I have a 3500 stall convertor in it now. I would like to try a 5500 but I don't know if it would be all that beneficial. A trans-brake might be more efficient.
You won't be able to drive a 5500 on the street without giving it a LOT of gas to get moving. A stall converter isn't about idling at the light. It's about launching the car in it's powerband. Whether you are racing or driving across town, you want a converter that stalls around the bottom of your powerband so that the engine is in it's working rpm before loading up uner the weight of the car. The higher you move your powerband with your cam choice, etc., the higher you want the stall so you don't bog before you make power. A friend of mine has a dedicated drag car with a 5500 stall that can barely move around the pits on it's own, but it comes off the line with the wheels in the air. He is putting in a higher gear to keep from running out of motor on the big end. I've used a 3000 stall on the street, but it was a gas sucking waste when I was cruising. You must stall below cruise rpm to avoid excess heat and wasted fuel.
when you get into the racing converters (over 3000 stall) then wierd things happen....some guys can drive certain converters on the street without too much trouble, they don't slip nearly as much as the rated stall speed makes you think they would. Also having a light car with a small engine means the converter won't stall as high as it would in a heavier car with a bigger (more torque) engine. Having a 5.13 gear means cruising rpm is gonna be way high anyways.
First quit calling it a "stall" converter!!! THEY ARE *ALL* STALL CONVERTERS!!! What you are referring to is stall speed: the rpm at which it starts to grab. You want a stall speed at the RPM that the engine starts to come on the power band. If it's an all-out drag car, you want a stall speed just below max power (more or less). Do the math on your engine & determine where the powerband is. ~ Paul aka "Tha Driver"
Call up some converter companies and talk to them, tell them what you have (in full detail), what you want to do, and get thier recommendations.
Just for comparision. Our Bonneville LSR (B/STR) runs a BBC (438 c.i.) in a '28 "A" Roadster Pickup. We use a TH350 trans. with a 1000 RPM stall converter. It idles off the line nice and smooth and "hooks up" about 500 feet out. We wondered if we were getting any "slip" at over 6000 RPM (engine), but the onboard computer (hooked to a wheel speed indicator and the engine R's comparator) says it's doing the "trick!"
More is not always better. I bought a bad ass used converter without really knowing what I was doing. Before installing it I called TCI, they had the serial number on file which told exactly when it was built and what it was built for. The stall was almost as high as my red line. It was built for a small cube, high rpm comp engine and it would have worked great in one. In my car it would have been useless. I won't pretend to understand the black magic of converter tech, but if it was an exact science you wouldn't see guys swapping converters all the time. Have you given your specs to a converter company, weight, cu in, cam duration at 50, gear, induction etc? Did they tell you approximately where the optimum stall speed would be? How high do you turn that 267? Right now you run about the same stall as I do but the combinations are very different.
I am gonna hafta make some calls. Right now it's crunch time on the Big Kauna Luau and I haven't had time to do jack.
my old boss ran a t/a dragster, 303 ci, alky,and 1800lb. (or whatever class rules were) with the "WhyBother" converter and a trans brake. It didn't do anything until like 6k and they ran 8's. that was 12 years ago, so don't quote me.
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