what is stall? what does it do? is it necessary? does my 700r4 tranny have it? how much?

 

stall is controlled by the converter. the amount will change with the weight of the car, among other things. basically stall speed is the point where the car moves or dies.

 

Stock stall speed for 700R4 is about 1600 RPMs.

 

Well, not quite. Stall is controlled by the converter, the motor, the car's weight, and the overall gearing.

A stock torque converter bolted to a stock engine has a stall speed of about 1600 RPM. That means, if you hold the brakes and mash the gas with the transmission in gear, the engine will spin up to about 1600 rpm and no further, until you let go of the brakes. When someone says you want "stall," generally that means you want a converter with a higher stall speed. So if you get a converter with a stall speed of, say, 3000, then your motor will rev to about 3000 before it "stalls" at that speed.

True stall specifications for a converter are changed by engine power. A stock V6 converter is not the same as a stock V8 converter, even if the car and transmission are the same. If you take a 1600-rpm stall converter from a stock V8, and bolt it to a stock V6, the stall will be lower, because the V6 has less torque.

When you modify your engine for more torque, your stall speed will go up automatically. When you modify your engine for more horespower, your stall may not change, but to get the most from your motor you'll want a converter with a higher stall speed.

A "torque" motor (like my 400 with a relatively mild cam) is quite happy with a stock stall speed. But a horsepower motor (like my previous 305 with the same cam specs) generally makes less torque at lower rpm's, and wants a higher stall speed so it will be much closer to its power band at launch.

Beyond stall, the converter's performance will vary with weight and gearing. A lighter car or lower (numerically higher) gears will make a converter behave as if it has less stall.

The best "stall" for my car will almost never be the best stall for your car. To determine the best converter for your car, you need to take into account the engine build, the rear gear, the transmission gearing, the car's weight, and the type of driving you intend to do.

I always tell people to gather up all the information they have on the car and engine build, and call the converter maker. It can be a bit confusing when you know you need a stall speed of 2800, but the maker tells you to buy a 2200 converter. But that's because they know that their converter will actually deliver a 2800 stall on your combination. Can't tell you how many guys I've talked to who are upset because they just looked in a catalog for a certain stall speed, but that's not what they got when they bolted it in.

There. Clearer now? Or clear as mud?