Torque Converter Advice

[Tommy-T]

This is a very interesting question.

First, you'll generally find the 260@.050 cams at the bottom of the street cam page. That means they're big.

My general rule from when I was street racing and there were no DOT racing tires...either you ran slicks or not. If you were going to run mostly street tires then I'd suggest just enough stall to keep the engine from stalling at idle or you having to press the brakes really hard to keep the car from creeping at a stop light. I'd rather have too low a stall speed to pull torque back slightly, though you could still blow the tires off, than get the motor into it's "torque zone" and assuredly blow the tires off.

I think any generic 10" street converter would do the trick, or a custom 11" designed for a true 2500 or so stall.

[cammerfe]

The C6 assembly area at T&C Livonia ended with a set of test stands through which all finished transmissions passed. Close by was a tank of transmission fluid that held a hundred gallons or more for the use of the test procedures. And immersed in the tank of oil was a heater that kept the temperature at 180 degrees.

When the oil temp goes up the life of the fluid goes down. I believe, for your combination, you need a 2500-3000 (max) stall speed and enough of a trans cooler to keep the oil at a bit less than 200 degrees maximum. The closer to 180 over the long term the happier you'll be.

You need a converter loose enough to not drag the engine down in stop-and-go and tight enough to not be a bother at freeway speeds. And of course you know that the SAME converter will act different if you change engine characteristics.

I'm sure everybody knows that 'stall' applies to engine speed characteristic and not to the converter itself. To speak of a 'stall converter' shows a profound ignorance of the topic. ALL converters have a stall speed. I DO understand the wish to talk in 'cool' shorthand but please demonstrate basic knowledge.  
 
KS

 

[james]

The C6 assembly area at T&C Livonia ended with a set of test stands through which all finished transmissions passed. Close by was a tank of transmission fluid that held a hundred gallons or more for the use of the test procedures. And immersed in the tank of oil was a heater that kept the temperature at 180 degrees.

When the oil temp goes up the life of the fluid goes down. I believe, for your combination, you need a 2500-3000 (max) stall speed and enough of a trans cooler to keep the oil at a bit less than 200 degrees maximum. The closer to 180 over the long term the happier you'll be.

You need a converter loose enough to not drag the engine down in stop-and-go and tight enough to not be a bother at freeway speeds. And of course you know that the SAME converter will act different if you change engine characteristics.

I'm sure everybody knows that 'stall' applies to engine speed characteristic and not to the converter itself. To speak of a 'stall converter' shows a profound ignorance of the topic. ALL converters have as stall speed. I DO understand the wish to talk in 'cool' shorthand but please demonstrate basic knowledge.  
 
KS

Well thank you very much for your help. I do have one question for you "cammerfe?" Why would you "presume" or "assume" I'm trying to be cool with my language? Im a 72 year old Vietnam Veteran just trying to have some fun in my twilight years. You do not know the operation of one's mind or the motives of their heart. In fact, I did say in one of my post I am not very knowledgeable on this issue, hence my question in the first place. 

[cammerfe]

I just went through this entire thread and didn't find a place where you said 'stall converter'. And I had no intent to point a finger at you in any way. There are things said in various threads that simply shouldn't be there and I'll cheerfully confess to, occasionally, bringing that sort of thing to the general attention.

I believe you're offended when you have no reason to be. But you have my most heartfelt apology in any case. (One of the reasons for smiley faces is to mitigate any potential 'bent' feelings.) I'll be 76 years old in another few days and I'm not a veteran of any war because I started wearing glasses in 1949 and I'm so blind without them that they wouldn't take me. I also don't know what that has to do with anything.
KS

[plovett]

Well, in any case be sure to let us know what stall converter you end up with, James.  I've heard ATI makes good stall converters so you might look there.   I'm pretty sure my next stall converter will be a custom one.  As you know, a good stall converter can make all the difference.  I do have an extra stall converter in my garage, but it stalled around 3800 rpm on my 428 so I don't think it would work good for your combination.  Whichever stall converter you get I hope it works well for you and stalls at the rpm you want it to.

paulie

[blykins]

I like stall converters.

 

[jayb]

Well, in any case be sure to let us know what stall converter you end up with, James.  I've heard ATI makes good stall converters so you might look there.   I'm pretty sure my next stall converter will be a custom one.  As you know, a good stall converter can make all the difference.  I do have an extra stall converter in my garage, but it stalled around 3800 rpm on my 428 so I don't think it would work good for your combination.  Whichever stall converter you get I hope it works well for you and stalls at the rpm you want it to.

paulie

LMAO Paulie!   

[plovett]

Stall converters are no laughing matter, guys.  If you get a bad stall converter, one that stalls at the wrong rpm, you won't be laughing.  I had a stall converter like that once. It stalled at the wrong rpm.  Not funny and not cool. In fact it was hot.  My engine didn't stall, but the stall converter did.  You could say my forward momentum was, well, stalled.  I'm just asking for a little maturity here???   

paulie

[james]

I just went through this entire thread and didn't find a place where you said 'stall converter'. And I had no intent to point a finger at you in any way. There are things said in various threads that simply shouldn't be there and I'll cheerfully confess to, occasionally, bringing that sort of thing to the general attention.

I believe you're offended when you have no reason to be. But you have my most heartfelt apology in any case. (One of the reasons for smiley faces is to mitigate any potential 'bent' feelings.) I'll be 76 years old in another few days and I'm not a veteran of any war because I started wearing glasses in 1949 and I'm so blind without them that they wouldn't take me. I also don't know what that has to do with anything.
KS

Well cammer, I accept your apology. Secondly, I did bring up the Vietnam thing because I'm grateful to be alive and your "chiding" me on such a "petty" issue of the word stall as in stall conveter. Thirdly, I don't really pay attention to the smiley faces.

[falcongeorge]

That's interesting, I've always thought the torque converter adds heat argument was overblown.  I run 6000 stall converters on a variety of cars, including my Mach 1, my Galaxie, and my Shelby clone, and take them on Drag Week where you are driving 200-300 miles per day, in all kinds of traffic conditions.  I never saw a significant rise in trans fluid temperature, 175 to 180 was typical.  My temp sender is in the transmission pan, which of course is not the hottest area, but nevertheless if there was extreme heat somewhere I think I'd have seen it on the gauge.  I always run #6 lines to a good, plate style transmission cooler (like an Earl's), positioned in front of the radiator.

For my part, I would not be afraid to run any stall speed on the street.

I have run 4500-5000ish stall, 8" converters on the street before, my experience pretty much parallels Jays. Maybe if you were running 3.08s or something stupid like that behind it, but with any sort of reasonable gear that makes sense for a car that NEEDS an 8" converter, I have never had a problem with excess heat. Honestly, at part throttle cruise, its pretty hard to tell the difference between a 10" 3500 stall and an 8" 4500-5000ish stall converter, unless you really goose it.

[plovett]

I have run 4500-5000ish stall, 8" converters on the street before, my experience pretty much parallels Jays. Maybe if you were running 3.08s or something stupid like that behind it, but with any sort of reasonable gear that makes sense for a car that NEEDS an 8" converter, I have never had a problem with excess heat. Honestly, at part throttle cruise, its pretty hard to tell the difference between a 10" 3500 stall and an 8" 4500-5000ish stall converter, unless you really goose it.

I would generally agree with that.  I think the confusion comes, at least in part, from a torque converter having a rated stall speed.  It's a number and it sounds like it's absolute.  "4500 rpm is the stall speed of this converter".  But the actual stall speed in use, depends on how much load you are putting on it.   If you have a "3000 rpm" stall speed torque converter, and you give it maximum load, like full throttle from a stop, it might actually stall at 3000 rpm at near zero mph. That's a lot of slippage.  With the same convertor at light throttle at 70 mph and 3000 engine rpm it will be slipping a lot less.  I don't know what it takes in terms of hp to cruise at 70 mph in most cars, but it has to something like 70-80 hp?   

I guess what I am saying is a torque converter stalls at different rpms depending on the load put on it.  That changes the slippage and torque mulitiplication.  That's part of what makes automatics so desirable in so many applications.  It's similar to a CVT transmission in that the true gear ratio is constantly changing. 

Still,  for any convertor over maybe 2600 rpm, I think an auxiliary transmission cooler and a transmission temp gauge are highly recommended.    You might also think about synthetic transmission fluid to help with the higher temps.

JMO,

paulie

[falcongeorge]

I have run 4500-5000ish stall, 8" converters on the street before, my experience pretty much parallels Jays. Maybe if you were running 3.08s or something stupid like that behind it, but with any sort of reasonable gear that makes sense for a car that NEEDS an 8" converter, I have never had a problem with excess heat. Honestly, at part throttle cruise, its pretty hard to tell the difference between a 10" 3500 stall and an 8" 4500-5000ish stall converter, unless you really goose it.

I would generally agree with that.  I think the confusion comes, at least in part, from a torque converter having a rated stall speed.  It's a number and it sounds like it's absolute.  "4500 rpm is the stall speed of this converter".  But the actual stall speed in use, depends on how much load you are putting on it.   If you have a "3000 rpm" stall speed torque converter, and you give it maximum load, like full throttle from a stop, it might actually stall at 3000 rpm at near zero mph. That's a lot of slippage.  With the same convertor at light throttle at 70 mph and 3000 engine rpm it will be slipping a lot less.  I don't know what it takes in terms of hp to cruise at 70 mph in most cars, but it has to something like 70-80 hp?   

I guess what I am saying is a torque converter stalls at different rpms depending on the load put on it.  That changes the slippage and torque mulitiplication.  That's part of what makes automatics so desirable in so many applications.  It's similar to a CVT transmission in that the true gear ratio is constantly changing. 

Still,  for any convertor over maybe 2600 rpm, I think an auxiliary transmission cooler and a transmission temp gauge are highly recommended.    You might also think about synthetic transmission fluid to help with the higher temps.

JMO,

paulie

As a rule, I prefer to refer to converters by diameter and "loose" or "tight", ie, I would usually say a "loose 9.5" or "tight 8", but when I do, lots of guys don't know what I am talking about. When in Rome...

[gt350hr]

   Stall speed is the rpm achieved before the pump, turbine and stator obtain "fluid lock". Modifications to the stator fins, pump and turbine fins , and their specific clearances are how "stall speed" can be changed ( up or down). For years the popular approach was the "J" cut on the back side of the stator fins. Recent times have resulted in leading edge cuts and even hand made steel fin units. This allows higher stall convertors to get incredible efficiency that was never possible "the old way". Many are still done the old way and do provide increased stall. A convertor like Jay uses is a perfect example of a modern high efficiency , high stall convertor. Increased fluid temperature is a problem with less efficient convertors as they are always "slipping" which adds heat. One of the most common ways to increase stall is going to a smaller diameter convertor . Many drag race cars use a 7" dia unit for super high stall. 8" is the "old standby" . 9 and 10'' units are designed for street/strip or the tighter versions for blown engines. Higher engine torque can also raise a given convetor's stall point as well as lose stall when the torque output is less that the convertor was designed for.
     Others may have different opinions/experience and that's cool too.
     Randy

[Falcon67]

You people quit stalling and get to the point.   

YMMV is the right idea.  I can drive the 20 miles or so without a problem - on a 75 or 80 something day.  In summer here, the road surface will be 140~150 degrees with an air temp of high 90s.  It'll cross 180 on the trans in a short time.  180 is my personal cutoff.  On the dragster - for sure more power but less load - trans temp goes from 150 to 180 in 660'.  The fight this weekend - temps in the 90s - was trying to get the lawn dart's trans temp back to 150 before the next round.  High speed blower pointing right at the trans case took 20 minutes.

[plovett]

   Stall speed is the rpm achieved before the pump, turbine and stator obtain "fluid lock". Modifications to the stator fins, pump and turbine fins

Maybe it would have been more correct if I said the slippage varies with load, rather than the actual true stall speed?

paulie