72cuttys

I am looking at the TCI Streetfighter converter, which is advertised as 3400-3600 for a big block. Given oldsmobiles' notorious torque, will it flash even higher? If so, would it be better to go with a Breakaway converter?

joe_padavano

I'll answer your question in a slightly different way. Published converter stall speeds are only a point for an estimated engine in front of it. You are correct in that the stall speed of a given converter is a function of the torque of the engine in front of it. An engine with higher torque will stall a converter at a higher RPM, but since you don't know the assumption that went into the published stall speed of your converter, you don't know whether the BBO has more or less torque than was assumed (though I would think you are correct and the BBO has more torque and thus will stall higher).

oldcutlass

It also depends on the spec's of your engine and gearing. Also is for street, track, or a combination.

joe_padavano

Sorry, but I don't see how gearing affects the stall speed of a converter. You stall the converter with the brakes locked and the rear end not turning. The only affect the gearing would have is that of making it easier to overpower the rear brakes, which has nothing to do with stall speed.

As for the specs of the engine, again, the only thing that matters is torque. Yes, the engine build will affect torque, but the actual metric that matters is torque at the flywheel, no matter how it is generated.

And while you are correct that intended use will matter for selection of the correct stall speed, that wasn't the O.P.'s question. The question was, will higher torque change the actual stall speed from advertised?

oldcutlass

Gearing, power curve, cam selection, and usage come into play on what torque convertor stall speed to use. Sorry.

dmullin

The OP may want to consider the losses incurred by a higher stall converter. Loss of effective torque multiplication, excessive heat added to the cooling system, loss of fuel mileage in a large fashion.






















These are things one would only be concerned with in a street car mind you.
This is also coming from a manual trans kind of guy. So take it with a grain of salt...

72cuttys

The car is/will be a weekend warrior, not a daily driver by any means so gas mileage is null. I am already planning on running an aftermarket cooler as well.

Motor specs are:
455 .060 over
10.5:1 compression
bone stock edelbrock heads
harland sharp 1.6 rockers
performer rpm air gap
870 street avenger

70cutty

Best thing you can do us call the TC manufacturer and give them your specs. They can recommend a best stall for your application. I called Hughes when I was buying mine and they were very helpful.
If you are not going to the track I would recommend 2500 stall which would flash around 2800-2900 with your setup. JMO.

oldcutlass

What cam? You might want to talk to some of the real performance guys on this, also ask about what brand torque convertor they recommend. The object of the stall speed is to get the rpm's at launch up into the correct part of the power band.

coppercutlass

I believe Jegs has a chart of recommendations based on gear and cam duration to get you what you need with an off the shelf unit.

72cuttys

Cam is a custom grind from cutlassefi based on the above specs.

241/248@.050 on a 110.
Lift would be .589/.565 with 1.6 rockers

70cutty

Instead of guessing call the TC manufacturer give them your specs.

oldcutlass

I would ask Mark what he suggests also. Whats the rpm range of your cam? What gears are you running? I'm curious to what brand and stall speed you finally go with.