Torque converters

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Valhallo

Well-known member
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My Car
73' Grande
In my quest to learning as much as I can about mechanics, recently I've been trying to understand torque converters. I get most of the basic concepts, but I'm having a hard time understanding stall speeds. From what I've read it sounds like you want a high stall speed if your car can handle it. It seems to me you would want the opposite though, right? Wouldn't you want full power being transferred through the drivetrain to the rear wheels as much as possible, without the car stalling? (which would be a low stall speed right?) It seems that would be most efficient.

It does seem like this part of the car could have a big impact on performance. Does anyone know what the stock 73 351C stall speed is?

 
Wikipedia has quite a bit of information:

http://en.wikipedia.org/wiki/Torque_converter

As does TCI:

http://www.tciauto.com/tc/torque-converters-explained

After you read those, look at this on YouTube:



One thing that wasn't explained well, is that the stall speed is controlled by the design of the torque converter as well as the power (torque) produced by the engine. If you stick a 4000 rpm stall converter on the 200 horsepower grocery getter you will never be able to achieve the designed stall speed.

 
I had always assumed the factory stall to be approx 1600 - 1800.

Currently, due to failure of my stock torque converter, I'm in the process of re-installing a NOS CJ torque converter I ran for a couple years about 10 years ago. My past experience with it had it hooking up at 2400. With a 3.25 Trac-lok, it's a very nice street setup.

 
In my quest to learning as much as I can about mechanics, recently I've been trying to understand torque converters. I get most of the basic concepts, but I'm having a hard time understanding stall speeds. From what I've read it sounds like you want a high stall speed if your car can handle it. It seems to me you would want the opposite though, right? Wouldn't you want full power being transferred through the drivetrain to the rear wheels as much as possible, without the car stalling? (which would be a low stall speed right?) It seems that would be most efficient.

It does seem like this part of the car could have a big impact on performance. Does anyone know what the stock 73 351C stall speed is?
factory 351 4v cleveland has a 3,000 rpm stall....Mine is a 1973 mach 1...351 4v....If you dont have that stall in your car and got a 4v cleveland like me...Your car will drop on its arse at every stop light and stall......Ford had to put 3,000 rpm stalls in our cars cause of the big racing heads....With out it.....Driving it in town would be a nightmare...Cause 4v heads are best from 3,000ish up too 7,000 rpm's...the 3,000 rpm converter is there to help keep your car driveable...Yet still have the git up and go it was intended for past 3,000 when the vert will let all the power hit you....but not if you have just a 2v..it will have a bigger vert...like 1800ish rpms

 
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Alright, those write-ups and videos were a good review of what I've learned in my research, and I now know that there is a difference between torque converters and stall converters. What is that difference? And the ehow said that the stall speed should be 80% of RPM when max. torque is reached, but why?

 
Alright, those write-ups and videos were a good review of what I've learned in my research, and I now know that there is a difference between torque converters and stall converters. What is that difference? And the ehow said that the stall speed should be 80% of RPM when max. torque is reached, but why?

A stall converter does what a torque converter does, but has a modified stator that requires a higher than normal rpm before it locks up. Lock up is determined by the amount of rpm the engine can achieve with the brakes on. Stall converters can be purchased with a wide range of stall from 1200 rpm to 6000 rpm. Ideally for the best launch or acceleration, the stall should be 80 percent of the rpm necessary for maximum torque. Stall converters are generally used in racing applications or towing applications, but it is not unheard of for a high horsepower street vehicle to be equipped with a stall converter instead of a torque converter.
 
Maximum "WHAT I"M ULTIMATELY LOOKING FOR" That's why I'm going with the 4 speed set up this time. Just hope my reflexes haven't deteriorated that bad.

 
Does anyone know what the stock 73 351C stall speed is?
From the 1973 Car Service Specifications, page 1 & 2:

351C 2V, C4 Trans, Stall Ratio 2.14:1, Stall Speed 1500-1700

351C 2V, FMX Trans, Stall Ratio 2.05:1, Stall Speed 1500-1700

351C 4VCJ, C6 Trans, Stall Ratio 2.16:1, Stall Speed 2200-2400

351C 2V, C6 Trans, Stall Ratio 2.05:1, Stall Speed 1500-1700

I can post id numbers if you would like them.

 
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Does anyone know what the stock 73 351C stall speed is?
From the 1973 Car Service Specifications, page 1 & 2:

351C 2V, C4 Trans, Stall Ratio 2.14:1, Stall Speed 1500-1700

351C 2V, FMX Trans, Stall Ratio 2.05:1, Stall Speed 1500-1700

351C 4VCJ, C6 Trans, Stall Ratio 2.16:1, Stall Speed 2200-2400

351C 2V, C6 Trans, Stall Ratio 2.05:1, Stall Speed 1500-1700

I can post id numbers if you would like them.
Nah, I don't need the ID numbers, but having the stall speeds is super helpful. Thanks man!

 
Torque converters and "stall" converters are the same thing. All torque converters have a stall speed. Like Roy said some have a higher stall speed than others. "Tight" or low stall speed converters are used in OEM and towing applications, "loose" or high stall speed torque converters are used in performance applications. Not to confuse things further but beyond stall speed is the "flash" speed, this is how far the engine speed goes when you stand on the throttle from a dead start. Flash speed is generally higher than the stall speed. One more thing, unless a torque converter has a special locking mechanism they never "lock up" there is always a difference between input RPM and output RPM, this is called slippage. This slippage creates heat, the higher the stall speed, the more slippage therefore more heat.

Just like with a camshaft, when buying a torque converter call the experts. Give them your car specs and what your intentions are and let them recommend the best converter.

 
Does anyone know what the stock 73 351C stall speed is?
From the 1973 Car Service Specifications, page 1 & 2:

351C 2V, C4 Trans, Stall Ratio 2.14:1, Stall Speed 1500-1700

351C 2V, FMX Trans, Stall Ratio 2.05:1, Stall Speed 1500-1700

351C 4VCJ, C6 Trans, Stall Ratio 2.16:1, Stall Speed 2200-2400

351C 2V, C6 Trans, Stall Ratio 2.05:1, Stall Speed 1500-1700

I can post id numbers if you would like them.
Nah, I don't need the ID numbers, but having the stall speeds is super helpful. Thanks man!
Many 1972 -1974 351C-4V CJ engines were mated to Ford's C6 automatic transmission. Ford used a special high-stall (3000 RPM) torque converter (D20Z-7902-A) and flywheel (D1ZZ-6375-C). Thats the convert mine has stock ...i still got it..Its a small little Green 3,000 rpm vert...If you got a 4v cleveland with a c6 auto..It realy needs it for them big heads..They wont flow right till 3,000 RPM anyways.

 
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I dont know how true this is, but I was always told that if you didnt know the stall of a converter you could tell a little by the markings on the outside of the converter. When you look at a converter and see those raised ribs on the housing, the more angled/leaning they are the higher the stall and the more straight up and down they are the lower the stall. Not sure how true this is but i heard it a long time ago and thought i would share it. One of those millions of bits of useless information floating around in my head LOL

 
Many 1972 -1974 351C-4V CJ engines were mated to Ford's C6 automatic transmission. Ford used a special high-stall (3000 RPM) torque converter (D20Z-7902-A) and flywheel (D1ZZ-6375-C). Thats the convert mine has stock ...i still got it..Its a small little Green 3,000 rpm vert...If you got a 4v cleveland with a c6 auto..It realy needs it for them big heads..They wont flow right till 3,000 RPM anyways.
1973 lists a D30P-7902-AA Converter for the 351-4V CJ @2200-2400.

I am only reporting what the book says.

I have spent so much time worrying about my engine, I didn't think about the torque converter. Glad this post came up.

 
Many 1972 -1974 351C-4V CJ engines were mated to Ford's C6 automatic transmission. Ford used a special high-stall (3000 RPM) torque converter (D20Z-7902-A) and flywheel (D1ZZ-6375-C). Thats the convert mine has stock ...i still got it..Its a small little Green 3,000 rpm vert...If you got a 4v cleveland with a c6 auto..It realy needs it for them big heads..They wont flow right till 3,000 RPM anyways.
1973 lists a D30P-7902-AA Converter for the 351-4V CJ @2200-2400.

I am only reporting what the book says.

I have spent so much time worrying about my engine, I didn't think about the torque converter. Glad this post came up.
http://reviews.ebay.com/ebaymotors/Ford-351-Cleveland-Engines-Key-Facts-amp-Information?ugid=10000000001410755 This from ebay motor guides.."which is wrong on some points}..Its a note at the bottom.....But i have read a few sites about the fords special 3,000 rpm stalls for these cars...And when i opened mine up..and compaired it too my freinds 2,500 stall..mine was smaller...Little green one..ill take a picture of it...but im not the first on this forum to talk about the special little vert than come in cobrajets and some other m code c6 small bells.

 
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http://reviews.ebay.com/ebaymotors/Ford-351-Cleveland-Engines-Key-Facts-amp-Information?ugid=10000000001410755 This from ebay motor guides.."which is wrong on some points}..Its a note at the bottom.....But i have read a few sites about the fords special 3,000 rpm stalls for these cars...And when i opened mine up..and compaired it too my freinds 2,500 stall..mine was smaller...Little green one..ill take a picture of it...but im not the first on this forum to talk about the special little vert than come in cobrajets and some other m code c6 small bells.
I understand. If one examines these books closely, there is bad information, missing information, misleading information.

And, when we get our cars, who knows who has worked on them or what parts they have put in...such as a windsor thermostat, or different distributor, etc. Most mechanics don't give a crap....they are working on the clock, this part fits, the car starts, get it out of my garage.

Forum members, especially "unsophisticated" ones such as myself want to be very careful. Your words/experience are appreciated.

 
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