Torque converter.

[oino]

ok, Other then the engin setup. Doesn't the rear gears and tire size play a part. My concern is that most of you run 3.54 ++ gears in the rear.
So ya the 3000 ++ converter is good.

 

[railroad]

I think you will be changing gears after doing some riding, probably 3.73 or 3.55. You can find a chart that will give you the rpm at given speeds. Most engines have a sweet spot (rpm ) for cruising. This can be just before the torque peak, which will make the T feel more responsive as you nudge the go pedal to pass or accelerate

 

[409T]

What gears in the rear?

3.50 rear end gears, 31" tires, th400 trans. Don't forget that the braking system comes into play as well. For example, a 5:1 pedal arm ratio will not hold a car as easily as an 8:1 ratio.

 

[oino]

Tech at B&M said, With the setup I have and without knowing the cam specs. I should go with a 2400.
He said if I could find out the cam specs that could change what converter to go with. He said in that light car a 3000 might be better. But again would need cam specs to tell me for sure.

So I'm working on getting them. Had my engine done 2 years ago. I've left voicemails for the place that did it. When it was done all they said it was an RV cam.

 

[Bennett]

I have a < 2000lb bucket with a mild 350, twin 390 cfm on a tunnel ram, 400 trans, 3500 stall converter, 2.93 gears, 31" tires and with only drum brakes on the front...No problems at stop lights.

 

[Lee_in_KC]

I have a TCI 3000-3200. I would not want anything lower than that. I idle at 800-900 with a moderate lope.

 

[Screaming Metal]

What the Mango said! Hahahaha.... ya know guys, you call these folks around these converters all day, maybe they have one in their car, that they drive. It has power brakes, A little slippage in the trans probably, alot of things are set up for the full body'ed street car. That 302 that trys to creep, probably a pretty good motor, has some power, thats gonna put more juice into the fluid in the converter. The trans is probably tight, either a good shiftkit, transkit, or a manual or performance valvebody. THAT, is going to keep the trans from slipping, and the converter isn't as loose as it ought to be. Makes for no-fun at a redlight.
Its best to go a little looser on your converter, than too tight, in a hotrod. Now, if your towing, you want things not as loose, that way the truck pulls against your load. after all, you got those big honkin' power or hydra-assisted brakes and a diesel. And for max acceleration, to pull agianst tall gears, you can go with lower stall speeds, but it will make great rear brakes a must though.
A top fuel car isn't as loose as most folks think, a top fuel motor maybe turns 9000rpm, and the transmission for a better lack of the word, is just a slip box, a series o clutches. You control max acceleration by watching that white mark thats on the side of the rear tires, and having that rear tire barely spinning for max acceleration.
If it were a straight trans without the slipping, it would either go up in smoke, the car would flip over backwards, even with the wheelie bars. or worse, tear itself in half, which has been done.

The guys at the shops saying 2500 rpm, probably under ideal conditions, with their trans, with their version of a motor, with a slight tailwind, with certain size tires....but they don't know T's like ya'll do. Having a little too much in a light car, the slippage isn't gonna be as great, because of the inertia it takes to get that bucket away from a light. And that motor pulling against that lighter load.
I just got thru with my new frame, I'm gonna be running a Big Blue Oval....Its gonna be a iron block with iron heads, 2x4's and a thumper cam, lake headers and I'm gonna set a 3000-3500 in mine. This one isn't gonna be trick, just a old fashioned hotrod made for driving. Something that I can drive to Ca. and back if I want.

 

[donsrods]

It's been my experience that the guys on all the tech lines tend to give you way too low of a stall when you inquire. I can guarantee you that if you put a 3000 in it will not be too much, even with a mild cam. It will also launch you a lot harder than you can imagine.

Don

 

[fordsbyjay]

It seems like the tbucketeers tech is better than then Transmission companies tech in this situation.... I wonder how many of those places you called have a tbucket?

 

[Mike]

Don't forget that the braking system comes into play as well. For example, a 5:1 pedal arm ratio will not hold a car as easily as an 8:1 ratio.

And we finally have a winner!

Jeff, you get the gold star for the day. ​

Fred, to answer your question, there are a lot of variables that determine and affect a converter's stall speed. First off, a converter behind a torquey big block in a heavy car will always have a higher stall speed than the same converter behind a 300 CID small block in a flyweight car. Unless we start changing other variables, like vehicle weight, rear gear ratio, low gear ratio, tire size, brake bias, etc. 409T has identified the biggest reason T-Buckets 'want' looser converters - brake bias is generally wonky.

A lower gear ratio will cause a converter to couple at a lower RPM. In most instances, a larger cam profile will cause a converter to couple at a lower RPM. A combination that works well at sea level will see a different stall speed at higher altitude. Changing valve lash .010" can make a surprising change in stall speed. As will changes in intake runner volume, lobe separation angle, compression ratio, header primary diameter and collector length. So some very minor differences can make a converter react differently in your car than it did in another car.

Don, you're right when you say most tech lines will err to the smaller side of things. But what most people do not understand is that the reason tech lines exist is to help potential customers with technical questions. And as much as people hate hearing it, my experience manning a tech line for 25+ years was naught more than proof the average call is a lesson in lunacy, rather than having technology at its heart.. The vast majority of calls to a tech line should be known as idiot calls, rather than tech calls. I'm not trying to cast aspersions on anyone, I'm just calling it as I saw it.

Torque converter selection is touchy stuff and there are numerous and seemingly insignificant variables that can really change a converter's personality. The average tech line caller doesn't know the critical variables, things like compression ration, stroke, rod length, cam centerline, runner volumes, header diameters, primary lengths, collector lengths, collector design, vehicle weight, rear gear ratio, trans gear ratios, tire height, etc. And, as I mentioned above, you can really change a converter by just adding .010" more lash to the intake rockers. Some people think knowing advertised lift and duration on a cam profile is all a tech line will ever need, but is the cam straight up, or has it been rolled one way or the other? And then, you ask the guy the really important question - is this a car that will always be driven on the street, or do you intend to bolt on a set of slicks and run it at a prepared drag strip? Because a car on street tires is likely never going to hurt a sprag, but a car that can really get the shovel in the dirt might grenade it. Then try to explain why the cost of the sprags are so drastically different.

So yes, the people manning the tech lines are generally in CYA mode. With hundreds of excellent reasons. All of them being on the other end of that phone connection.

 

[oino]

ok 3000 it is.

 

[RPM]

l Because a car on street tires is likely never going to hurt a sprag, but a car that can really get the shovel in the dirt might grenade it. Then try to explain why the cost of the sprags are so drastically different.

What really hurts is that sprag coming through the case and the floor. Like stepping on a land mine, just don't know were all those little pieces of steel are going.