Advice on torque converter and stall

[CZ-75]

Higher stall is fine, but you better get a lockup tc if you plan on freeway driving. Otherwise, the converter will be slipping to it's stall speed while in overdrive, and it will build heat and nuke the trans.

That is exactly why I went with a 2200-2400. I decided to go with 3.89 rear end, so with a .70 OD I will be somew here just north of 2500 RPM at freeway speed.


Oh, and the shop will also be adding a cooler just in case. Plus, Dan at Silverfox Performance Transmissions custom build s the valve body to improve fluid flow

 

[hyena429]

Do I care about launchability? Not really - I'm not planning on racing. So... why do I 'need' a higher stall-speed TC again, anyway? Seriously - I don't get it. You keep making arguments that support racing or launching (which is probably fine for CZ-75 - sorry to hijack

I'm not talking about just launch...You're car can flat out back fire and die with out the right stall....I'm just talking about a decent take off from idle...Sorry if you miss understood what i ment about launching...just a good healthy take off is all.

Not tring to start a fight...I just dont want to see some one make a mistake and put the wrong converter on a 4v motor is all. A stock 89 gt mustang 302 has small valves and heads compared too a 4v cleveland...So it needs less stall.

When you're heads are very large inside it struggles at low RPM's too keep the gas atomized....If you give it gas and you have wrong converter..boom..Your car will either die on the spot or back fire or struggle to get going.. ..Right converter will stop that from happening..It lets your motor rev and keeps the gas atomized till it can use it properly before it has too much load...It will save you from any stalling....So if your runing a 4v motor you should have more than a 1800 stall...It needs a 2200 "or more" to run right in town.

It pretty much comes down to the size of the valves and passages in the head.....Most 2v's even with alot of horse power will still have a lower sweet spot than a mild 4v motor...Smaller valves can keep gas atomized better at low RPM..Passages in head are smaller..So higher velocity at low RPM...With big valves and big passages like 4v, the velocity is too slow at low RPM's...The gas will pretty much turn into rain and fall out of the air...and car will fall flat on its arse when you put it under load with wrong converter.

Decided to go with a 12 inch inverter with a 2,200 to 2,400 stall, which should work better given my application.

Sounds great for your motor.

 

[PAPPY HAROLD]

I think you guys are on it now!!! And yep on the heads and valves Maybe I should have included that, my heads are big valve and ported. WAY TO GO GUYS.

 

[Don C]

There's a lot of factors that go into torque converter stall speeds, not only the design of the torque converter, but also the torque produced by the engine and the weight of the vehicle. Properly designed torque converters also have little slippage at highway speeds, with normal power. However, stepping on the throttle to speed up or climb a hill will increase the slippage. Even though the "slippage" is entirely in the transmission fluid heat is still generated, and efficiency (fuel economy) is reduced.

As mentioned in other responses the torque converter must match the torque range of the engine.

I would also use the lockup feature, the only time you don't want to use it is if the power you are developing is too high and you have to use the solid input shaft.

Attached is an article from Classic Trucks that should help.

How Torque Converters Work.pdf

This link is to torque converters from a diesel engine point of view, and gives a good description what happens when the stall speed is too high:

http://www.bankspower.com/techarticles/show/10-understanding-stall-speed

 

[Mister 4x4]

Thanks Guys... for not taking my questions and lack of understanding out of context. ::thumb::

Torque Converters for me are one of those things that just fall into the category of 'F.M.'

I'm still planning on running the stock AOD TC initially (especially since it's already in the car and I really don't want to pull it apart - it's all about moving forward, ya know?). If it becomes a problem once the car is rolling under its own power, then I'll worry about getting something more appropriate (if required).

 

[wwhite72]

Performance Torque Converters in Muscle Shoals, AL built me a nice one for the FMX. i believe it is 11" with a 2500 stall. works just fine with my 3:25 tru-trac rear. Though the CHI 2V heads, Crower hyd roller cam and dual exhaust give her a bit of torque so the stall speed is fine. i guess if i went to 3:50's i might want slightly higher but i have to use highways to get anywhere around here. in traffic she rolls off idle just fine and starts to growl a bit. when i put my foot on it the rpm's shoot up much much faster than the oem which was around 1800m i am told. there is a slight shift kit in the throttle body but nothing too stiff. It was installed last fall so i dont know if there will be a heat problem in the summer.

 

[Totalled]

Thanks Guys... for not taking my questions and lack of understanding out of context. ::thumb::

Torque Converters for me are one of those things that just fall into the category of 'F.M.'

I'm still planning on running the stock AOD TC initially (especially since it's already in the car and I really don't want to pull it apart - it's all about moving forward, ya know?). If it becomes a problem once the car is rolling under its own power, then I'll worry about getting something more appropriate (if required).

You will likely be fine. Generally, the more torque and engine makes, the higher it will stall a torque converter, than the same torque converter behind a smaller engine. So you will likely have a higher stall speed with your 351C than the stock 302 would have anyway.

 

[turtle5353]

I was running a 3000 stall converter from B&M in my old 351c 2v and it seemed to work great. I drove alot around town and back and forth to work and hardly even noticed it in there. Its a c4 trans with a bowler valve body and 373 gears. My cam specs called for atleast 2800 stall so i went with the 3000. I am going to be running the same converter with my 408 stroker. We will see how the c4 hold up to that and how the converter likes the extra torque. Heres the link to my converter at summit. http://www.summitracing.com/parts/bmm-50436/overview/make/ford

If i grenade anything in the near future with this motor i will definatley be building and aod for the 408.