Hot Rods Should have gone with a stall converter ?

Well, we've come down to a matter of semantics. The same term can have different meanings or references depending on who is using it or how it is being used.

Stall speed can refer to the absolute highest rpm the engine will achieve against the toque converter in a situation where the turbine is held stationary. That is the way we used the term in the equipment business when I turned wrenches. The converter stall speed was recorded when new and that was kept in the history file for the machine. Later one when there was performance issues the converter stall speed would be checked again and compared to the base line, which is a great piece of information when diagnosing a complaint.

But another more common reference when using the term is the point where the car drives through the brakes, because many (most?) cars braking systems, especially on older drum brake equipped cars, will not hold completely against full throttle application. And apparently that use of the term has given way to what some of us used to call the flash speed, that is the rpm the engine reaches under full throttle acceleration from a dead stop prior to the point where the converter stops slipping (the impellor and the turbine speeds are equalized). I think this is the common usage of the term today. That is why weight of the car is a factor.

 

I hate to argue with you, but actually the stall speed would go down, as the higher HP & torque would get the car moving much more quickly and at a lower rpm. The converter would lock up earlier and the engine would never reach the same RPM under acceleration as with the lower HP engine.

Higher HP would have the same effect as reduced vehicle weight.

 

Yeah, but going the circuitous route is far more fun! Picking up linguistic treasures along the way!

Chris

 

This thread is quite informative especially with all the jocularity.

 

Yeah, what he said. Lippy

 

Now for a non Webster reply. "Picking fly sh** out of pepper".

 

Shit...I got potato chips in my overalls

 

How fast is your idle? 700 RPM? maybe lower the idle a little bit.
Yes a mild stall converter (like 200 -300 above stock) makes them easier to drive. On a light car like an A or a T one that locks up early overrides the brakes as a rule.

 

Also, how is the mechanical advance reacting?

 

A trans brake, loose converter, manual valve body can be a heck of a lot of fun. My large " BBC likes to eat converters for lunch. Getting a custom bolt together made for it now. Current 4000 rpm stall goes right on up to the rev limiter at 7000. Still drives as it should, this off the shelf converter just cannot contain all that torque.

 

Wow, Now my head is spinning Thanks for all the reponses. Before I do anything I will lower the idle down a bit more & mess with the timing. And yes could be a issue with the brakes. Have vacuum boost brakes but I still have to stand on the brakes to slow down. As one mentioned with the same problem its scarey pulling out of the shop running with the way it is now.
Yes,Is a 350 CI 290 hp crate motor Never thought the cam would be a issue when I bought the motor, but now that it,s in and running does have quite a loop/overlap. 76 yrs old and still learning and making lots of mistakes,unfortunately mistake s cost money and frustration.. Gene in Mn

 

I had a man sometime in my past, can really remember who or where it was, but I remember his explanation of a torque converter. Real simple, but may help folks understand how a torque converter works.
He explained it this way: take two window boxes fans ( hope you all know what these are) put them together on the floor. Turn one on low, the second one may or may not turn. Put the first on high, the second will turn! How it turns depends on the speed of the first fan and the pitch of the blades on each fan! The first fan is your engine, the second is your transmission.
Of course, in a torque converter, the blades are closer together and running in ATF, but the principal is the same.

Maybe this simple example will help in understanding basic torque converters.





Bones

 

You need a tuning tach, one with a low rpm range, not a dash tach that goes up to like 8k rpm, which will be inaccurate at 600 - 800 rpm. As Squirrel posted, spend some time tuning the idle quality (make sure the timing is correct, and then fine tune the idle speed & idle air/fuel mixture screws.

 

Not to be pendantic but what you described is really a fluid coupling, not a torque converter. A torque converter adds a third element between the 2 fans which redirects the air (oil) flow so that it hits the blades of the second fan with more force. This is the secret with torque converters and is what enables them to increase the torque that is fed to them from the engine. The torque output is greater than the torque input, and is one reason why an automatic is faster than a manual shift.

 

Blues4 U, you liked that word too!! I’m going to use it as soon as I can.....so I don’t forget it! Lol
Yes , I understand that my example was very simple, maybe too simple too accurately describe a torque converter. But, it still describes the basic principles of the torque converter. If both fans had the exact same pitch on the blades , yes , it would be a “ fluid coupling” , but if the second fan had more pitch, it becomes a “torque converter“ . That is why I mentioned in my post that how the second fan turns depends on the speed of first fan and “the pitch of both fans” . For simplicity I did not mention the other plates that redirect the oil flow in an actual torque converter.
Sometimes looking at the inside of a torque converter can be confusing.






Bones

 

I still want to do a switch pitch before I die...

 

So took a fellow racer's convertor. He ran a 406 SBC, pretty stout. He had a 5000 RPM 8" convertor. I ran a really stout 477 BBC in a lighter car by about 150lbs. For my combo I got 5500 out of it, which is exactly what I wanted anyway. I'll admit that some of my experiences and recollection of data are slightly skewed by decades old cobwebs, but in simple terms the more badass the car the higher the stall speed would go. And true enough, just running around in the car at meets and shows I had no issues with excess slip, but higher stall nonetheless. Same with the old Vega converters used in street racers. Big blocks got near or over 3000, small blocks a bit less. Still, the point is to know how they arrived at stall speed, at what TQ value.

 

This is dead WRONG on how any given converter reacts....with a higher torque output motor, stall speed goes UP, always.

The higher torque and power does get the car moving faster, but at the initial hit and first second of acceleration it will stall the converter HIGHER. It may reach the coupled speed sooner, but that doesn't relate to how it reacts to initial power input.

It does not react the same as removing vehicle weight.

You take a 10" diameter "3500 stall" converter that makes a true 3500 rpm stall behind a 283 or 305, and put it behind a 632 Big Block and it will likely stall 5500+ rpm, and may never even be able to fully couple due to the larger engine making flat out more power than the converter design can even deal with, and it will still be slipping badly at the finish line despite even being at 7000 rpm..

 

You know, you got me on that one.

I was going with this from Phil Parsons, which if that is THE Phil Parsons, and not just some random guy on the internet that shares the name, I figure he knows a bit more about the subject than either of us.

See: http://www.hardtail.com/techtips/selectingconverter.html

But then I kept digging, and I came up with this source, and in this article he says: "The new ATI converter is flashing around 3,500 on motor and a more manageable 4,000 on nitrous." Hmmmm, that's the opposite of what Mr Parsons said.

See: https://www.dragzine.com/tech-stori...-goes-into-stall-speed-in-a-torque-converter/

So, I back off of my earlier post. I thought I had it straight in my mind, but am now conflicted.

 

Push the gas pedal down slowly (when the car is stopped, in gear, brakes on), and the more you push, the higher rpm you get.

 

The vacuum modulator function can have much to do with these type of problems when a hot cam and low idle vacuum get involved.
I’d check that out really well.

 

Blues4U,.... There are more than a few things wrong in the Phil Parsons article....would make me believe it is not the famous NASCAR racer but just some random dude on the internet....but I've met more than a few circle track guys who don't really know some of the stuff us drag racers or street/strip guys know well. Same is true for the drag guys knowing circle track info.

The Brian Wagner article is on point.

 

We are getting there. Any “ stall” torque converter has a “ rating” , such as a 2800 rpm stall torque converter. This is higher than most stock converters, but even stock converters have a “ stall” rating. This is just a reference point. It has nothing to do with the brakes on your car and at what time it will pull through the brakes. One of the reasons this won’t compute is the torque converter has no idea of what the rear end ratio is. Things would happen at different times between a 3 to 1 vs 4.56 to one rear end. And it does not know the horsepower/torque of the engine it is going on, which will change the “ stall “ speed.
The stall number , is just a guide line to compare the torque converter to other torque converters, for the selection process. When it actually “ stalls” is dependent on many factors and will vary.








Bones

 

I have a DD car and a turbo diesel p'up with At, but both my hot rods are manuals,and the only light car with a modified engine was a late friends "A" coupe with Z3 crate engine and 2004R which drove normally when I was offered a chance to drive it. Dunno about the converter, whether high stall or stock.
One extreme years ago created an intense dislike for high stall speed converters in a street car. We had kin folks to our home (this was back when I was married). Needed something from the store and BIL's car was last in line in driveway and I used it in town traffic to go to Home Depot across town.
Car was a late 80s to early 90s Impala with an SBC with some mods and a high stall speed converter, and I hated that damn car by the time I got back home! Never knew details on engine or trans as he had just bought it.
At the other extreme is my OT turbo diesel p'up with a torque peak @ 1600 rpm and a very low stall speed converter. The "creep" at computer controlled idle speed approx 659 rpm is such that I have to keep firm pressure on the hydraulic boosted brakes, and I just slip it up in neutral if it figures to be a long light.
I do however find this thread interesting in that I'm now 82 and left leg is getting weak and may one day force me to AT on hot rods
Going to install a dual disc clutch in the "A" Hiboy as a last ditch effort to find a clutch I can depress that will handle the engine and last awhile.

 

Then there’s converters considered “loose” and “tight” ones.
Loose ones slip a lot, they will move a car but a face up nickel will stop it until the RPM comes up. You need plenty of throttle to climb a small hill or up a trailer ramp.
Tight converters appear to drive similar to stock in normal conditions but allow plenty of slip under sudden high torque events.

If you’re hunting an off the shelf high stall converter it’s going to have an advertised stall RPM in big bold print. Somewhere in the fine or print footnotes it should say what they measured that RPM against. If you call for a custom converter they are going to ask you A BUNCH of questions to help get you what you want. I’m not sure how to say it without getting too wordy but those questions and answers should be provided as specs for the test mule to arrive at the rating for the advertised stall on the off the shelf converter.

I deal with these guys,
http://www.perfectconverterco.com/products.html
Local and fast turnaround

 

Thats the only time I notice my converter. Loading it on a trailer or pulling into my garage, which is on a slope. Need to be careful loading on the trailer for sure, lots of left foot braking.

 

Even stock converters have different “ stall” speeds. Usually big engines have “ tighter “ converters. Torque converters make a lot of difference in the performance of a vehicle.
I had a slightly ot pick up truck with a 300 six C4 3.54 track loc rear end low profile 12 inch wide mud grips. This truck would move the world. Was unbeatable out of the hole. Took a lot of “ high performance “ cars, for about a hundred feet or so and could pull anything.
But it always had a vibration. I had to pull the engine and noticed that the Gold colored torque converter was machined crooked! You could actually see it! Aha, found my vibration, by accident. I replaced it with a known good one out of a 289 v8. Total different truck, gutless out of the hole, hook it up to something to pull, nothing! But it got better gas milage! With just a torque converter change.








Bones

 

This is more fun than a pinion angle thread

 

Or even a patina thread....