Torque Converter Stall Speed

[jmccrack]

Hey guys.
I have ordered my engine and tranny combo. EFI Stroker 350 with a Streetfighter 700R4 Tranny and a 2000RPM stall. In relooking at FFR suggestions they recommend a 3500 RPM stall. Reason with a truck this light you can drive right thru the brakes at a light. I am looking for any suggestions or other thoughts.

[Pat Landymore]

I have a 3000 stall converter in front of the Powerglide in my big block powered 35.

3.55 gearing and approx 900-925 idle speed. Doesn’t clunk/lunge going into drive and takes very little pressure on the brakes to keep it from moving.

Perhaps if I had 3 or more gears (deeper first gear ratio) another 500 rpm stall higher might be required make the combinations feel equivalent...?

My 2 cents

Late game update...my converter is 9”. Larger will pull harder at idle. Also different viscosity trans fluid will skew stall speed and rpm thru the traps. Thicker = lower RPM.
Sorry for late game update.

[Bob Cowan]

I think you'll find a 2K stall is way too low. I have a 3,200-3,400 stall. It works well, But I think 3,400-3,600 would be a little bit better.

[NAZ]

You're not going to be happy with that converter. Call Hughes (AZ) or ATI (MD) or FTI (FL) and discuss what you need for a torque converter in that light car. My guess is closer to the max torque RPM would be a good start. Most folks don't really understand stall speed and pick one out of a catalog that's too low. Think of stall speed as a concept not an absolute as many things affect what speed a converter will stall at. I run a loose converter that stalls ~6000 RPM down in PHX on a winter night but up here at 7,000' ASL it will stall at ~5000 as my engine makes significantly less torque in this thin air. So don't think you can just order one from a parts house and it will stall at the advertised RPM in YOUR car. And even with a loose converter like mine, the car creeps forward at idle when on level pavement and no, it doesn't run at 6000 RPM when cruising down a city street -- converters don't work that way. Better to get this squared away now before you assemble everything or you will be doing it twice.

And don't forget to ask the converter builder what BTU trans cooler you should run with your new converter.

Good luck.

[JimLev]

Ditto to all of the above.
With my LS3 and 4L65E tranny Tony recommended I use a converter from a 4L70 tranny.
The stock (4L65E) converter is 2400-2800 RPM, the one I bought (4L70) is 3000-3400.
It stops fine using one foot even at a fast idle when cold.

[cob427sc]

I have been researching this issue since posting on another thread. I built my 33 using a buick nailhead engine with a stock converter and trans. When the engine is cold and idling at 900-1000 takes nearly both feet and an anchor to stop. Easiest way is dropping into neutral first. I've been speaking with various convertor builders and there are a lot of items to consider when selecting the correct convertor as Naz states above. Engine, cam, intake, torque rpm, gearing, rear tire size and proposed use of the vehicle. I'll get there this winter but it also seems like between the different suppliers they all recommend different stall speeds given the same information.

[Brave Salmon]

I installed a new BPE 347 fuelie a year ago in my 33. Car weighs in at 2480 wet. I took the "advice" of the FFR guys and ordered a 3200 stall for my AOD tranny. It was a huge mistake for me. It felt like I had to rev way to high just to get moving. I was really disappointed so took the car to a custom converter shop in Sacramento near me. He said that speed was way to high for a combo like mine unless I was planning on drag racing the thing. I was PO'd but went ahead and pulled the 3200 out and had him build me a new 2400 unit. I have never been happier with the results of any other single job I farmed out like I have been with this converter. The car operates like the family sedan from a stop, brakes perfectly, and performs great on long 300+mi drives. They don't have a website pre se, but they are on Facebook under D&P Torque Converters. Owner is Matt and he is very reasonable and the guy has been building nothing but converters in the same shop for over 40 years. You wont be sorry.

[Pat Landymore]

I have been researching this issue since posting on another thread. I built my 33 using a buick nailhead engine with a stock converter and trans. When the engine is cold and idling at 900-1000 takes nearly both feet and an anchor to stop. Easiest way is dropping into neutral first. I've been speaking with various convertor builders and there are a lot of items to consider when selecting the correct convertor as Naz states above. Engine, cam, intake, torque rpm, gearing, rear tire size and proposed use of the vehicle. I'll get there this winter but it also seems like between the different suppliers they all recommend different stall speeds given the same information.


That’s an awesomely cool choice of engine! Have long wanted to do something with a roots blown 401 or 425 nailhead. They’re a great looking motor. 👍🏼👍🏼

[cob427sc]

The engine choice was kind of driven by it's appearance and the fact that it would be different from anyone else. Running 3-2barrel intake and just added the hood top section with the air scoops poking through. I'm really happy with the engine and in general with the tranny except for the stoplight issues and hopefully with a convertor change will make me really happy.

[narly1]

Reading this thread and others on the subject I'm finding that the information seems to be conflicting and confusing.

The one take-away that I've gained so far (and correct me if I'm wrong) is that there's a huge variation in TC manufacturers stated and actual stall speeds.

I get that altitude and temperature effects can partially account for this difference.

In the end, what are the group's thoughts on collecting info on what works.

The expense of changing TC's is not crazy huge, but the time and effort hassle of doing the swap seems to be more of a concern.

To this point the sentiment of many posts seems to be "I want to get it (stall speed) right the first time, and only buy/install once."

From what I've read previously would a larger list of posts indicating engine displacement/HP/torque, transmission model, axle ratio, TC brand/model/stall speed, and either temp & altitude or location (to get an idea of the former) help?

[Pat Landymore]

I think what I’ve learned from this thread is that using ‘stall speed’ to choose a torque converter is like using the (thankfully...) long lost terms of 3/4 race/full race to choose a camshaft.

It seems it would be much more helpful for a lightweight street Rod if they had a specification such as ‘idle coupling coefficient’ to advise for a given stall speed, at idle speed ‘x’, how tightly the converter couples, which is really the issue we’re talking about. Most likely the major mfrs have this info but they’re not sharing it publicly.

Know a couple majors do have ‘street Rod’ converters, which indicates they are aware of the issue.

Ultimately if you’re this concerned you should select 2 or 3 mainstream manufacturers, speak directly with them and then choose an average of what they suggest.

I got lucky I guess....

[FLFrank35]

I ordered a Ford 306 and AOD from BluePrint, and they selected a 3500 stall converter for me. The mounting holes would not line up with the flexplate and I could not find a flexplate with the proper hole pattern. So I was put in contact with Bill Schmidt at Performance Automatic (who supplied the AOD/converter) and he sent a 2400 converter. I told him FF and BluePrint recommend a 3500 stall due to the light weight of the finished truck, but he said I'd be fine with the 2400.

This is my first build and I don't have any transmission experience, so I took his word for it...I hope I don't regret it. So far, on test drives without the complete body, it wants to move from a stop but not too bad. And the brakes seem effective enough, for manual brakes.

Frank

[narly1]

Anybody running a SRF8082AOD from FTI? I have a chance to pick one up here locally for a good price but only if it is going to work well in a FFR33 w/ 302 ~ 350 HP & AOD trans.

Questioning the 4000 rpm stall rating.


Earl

[Brave Salmon]

Earl, see my earlier post regarding stall speed. I like the 2400 converter I have because I do not race it or drive it like I stole it. Since stall is really a matter of feel more than logic, I suggest you err on the side of driveability vs high speed operations. How are you going to drive the car/truck is what matters... if you want to jump in, start it up and go like your family sedan,, then you'll be disappointed in a high stall converter. If you want to do high speed tire chirping shifts and burnouts at every stop sign, then go with high speed. Your decision..

[narly1]

Earl, see my earlier post regarding stall speed.

Thanks I think I'll take a pass on this local deal then.

Earl

[Brave Salmon]

If you want to call my guy he's in Sacramento, ca. That's not Canada I'm afraid. I could call him and ask if he has a contact in your neck of the woods, just say so. Of if he ships to the great cold north..