Torque Coverter thoughts

[2015ghost]

I'm looking for information regarding stall/torque converters.
the question I want answered is, Why do I need X stall converter if I install X camshaft?

Ok, so my 79 Camaro had a 327cdi with a 292/.512 hyd cam. I had no stall in it, and it would not lug or lurch while in gear at a stop.
My current car is a 2015 SS and I'm looking at a SS3 GPI cam.

To my knowledge the point of a stall converter is to get the motor to flash up to X RPM to get into the power range of the cam when it's floored. In my research people with a stall did not have any drivability issues. To me this means that the point where the converter starts pulling the car forward under part throttle is still 1200-1500RPM, which is exactly what is seems to be doing stock.

• If the stall moves the normal engagement point along with the stall RPM in correlation, then wouldn't a car with a 3500+ or whatever become un drivable because it would continue to slip until like 2000RPM?

Can someone please fill me in on what I'm missing.

[DSX_Camaro]

Extremely small scope answer: it isn't lugging, it's surging. It's just unpleasant to drive. Talking about converter vs cam choice for daily driving, nothing to do with racing.

[2015ghost]

I don't understand your statement.

[DSX_Camaro]

It's not going to stall with your foot on the brake. But when you let your foot off the brake and start to ease in to the gas (assuming you're driving it daily and not mashing the gas), it's going to surge. In context with what you've said, perhaps lurch would be the word you would use. It won't accelerate smoothly from a stop, it will jump forward. Might also have to do with slip and lock up in higher gears, but I honestly don't know for sure.



Since I have a V6 I don't have an exact answer, just what I've read from other SS posts. I know neither how to describe it nor explain how the drivability changes with a properly spec'd converter. I just understand gears vs cam vs converter choices on paper.

[Chris49066SS]

Originally Posted by 2015ghost

I'm looking for information regarding stall/torque converters.
the question I want answered is, Why do I need X stall converter if I install X camshaft?

Ok, so my 79 Camaro had a 327cdi with a 292/.512 hyd cam. I had no stall in it, and it would not lug or lurch while in gear at a stop.
My current car is a 2015 SS and I'm looking at a SS3 GPI cam.

To my knowledge the point of a stall converter is to get the motor to flash up to X RPM to get into the power range of the cam when it's floored. In my research people with a stall did not have any drivability issues. To me this means that the point where the converter starts pulling the car forward under part throttle is still 1200-1500RPM, which is exactly what is seems to be doing stock.

• If the stall moves the normal engagement point along with the stall RPM in correlation, then wouldn't a car with a 3500+ or whatever become un drivable because it would continue to slip until like 2000RPM?

Can someone please fill me in on what I'm missing.

Your '79 was several hundred pounds lighter than your 2015 SS. With a car as heavy as a 2015 SS, a stock converter behaves completely differently than a performance converter with a higher stall speed. With a higher stall speed, you will be able to launch at a higher RPM and stay in the powerband of these engines (LS3 and L99) Speaking of older school Chevy Hot Rods, Christianchevelle, chime in anytime, this is your forte

[2015ghost]

Chris, you have a 4K converter, with a stage 4 cam. So when you leave a stoplight how much RPM before it moves you? I hear the stumble or lurch thing is common with stage 3 and above. So it’s saying that a stall has more give to soak up the lurching?

[Chris49066SS]

Originally Posted by 2015ghost

Chris, you have a 4K converter, with a stage 4 cam. So when you leave a stoplight how much RPM before it moves you? I hear the stumble or lurch thing is common with stage 3 and above. So it’s saying that a stall has more give to soak up the lurching?

My idle keeps me at 850 rpm. There is no lurching. A normal pressure on the brakes keeps the car in place without any issues, but the car has the shaking and rattling side to side. When I take off at a stoplight, driving normally, the car accelerates, but the rpms quickly rise to about 2500. The converter lets it slip, but with the gears, it still gets up and goes pretty quick. When I lay into the throttle, it gets up and going, but starts really pulling around 50mph. My brake stall is about 3300 rpm before the wheels start to feel like they are going to break loose. At the strip I can stall it up to about 3300 before the wheels start to feel like they are going to break loose.

[Chris49066SS]

Ok, so I was driving today and looked at the tach so that I could give you a better answer than yesterday. Idle is right around 850rpm, generally bouncing continuously between 800-900. Again, there is no lurching with my foot on the brakes. Letting off the brake completely, it will move forward a little and the movings forward match the chop/rpm rise. Driving normally from a stop, it goes up to about 1800 immediately as I start moving but quickly rises to 2500 and climbs depending on how much throttle I give it. It sounds like its winding up; this is the converter slipping as its supposed to, being a 4k converter. Driving it conservatively, its getting up in the 3500-4000 range, again depending on exactly how much throttle I give it. The rpms don't drop upon upshifts, so it has that winding up/3500-4000 rpm continuously, up to 45mph in Sport mode, 38mph in Drive, then it drives more or less like stock, as long as you are driving it conservatively. Same with freeway driving. When the converter is locked, its not slipping anymore and drives similar to stock. Finally, WOT. So for WOT, taking off or throughout the 0-100 mph range, when I hit the gas, the rpms rise very quickly. As in almost instantaneously, it can be 1200 rpm, then when you hit it, it shoots up into the 6000 and up range, shifts at 7300, and drops to 6000 and climbs again. So it is, at WOT, always in the 6+ range. One more thing on WOT, it has plenty of get up and go because I have 3.91, that pairs with this setup well. But its when you do get up and moving, around 50mph when you feel it putting you back in your seat. Its a very streetable setup, but is definitely set up a little more toward top end power and racing. Hope this helps answer your question.

[Joe M 2012 2SS]

Originally Posted by 2015ghost

I'm looking for information regarding stall/torque converters.
the question I want answered is, Why do I need X stall converter if I install X camshaft?

Ok, so my 79 Camaro had a 327cdi with a 292/.512 hyd cam. I had no stall in it, and it would not lug or lurch while in gear at a stop.
My current car is a 2015 SS and I'm looking at a SS3 GPI cam.

To my knowledge the point of a stall converter is to get the motor to flash up to X RPM to get into the power range of the cam when it's floored. In my research people with a stall did not have any drivability issues. To me this means that the point where the converter starts pulling the car forward under part throttle is still 1200-1500RPM, which is exactly what is seems to be doing stock.

• If the stall moves the normal engagement point along with the stall RPM in correlation, then wouldn't a car with a 3500+ or whatever become un drivable because it would continue to slip until like 2000RPM?

Can someone please fill me in on what I'm missing.

The reason you need a torque converter with an aggressive cam is so your car will stay in powerband when launching and changing gears.

An automatic car that has an aggressive cam in it will "lug or lurch" with a torque converter that has an improper stall rating for it.

After installing a higher stall speed converter, you will have to bring the RPM's up higher to get the car to move during stop & go driving, and the transmission will build more heat due to the higher slip. This is why you have to put a transmission cooler in. Heat kills transmissions, and a good tranny cooler will keep your temps under 185*.

Gears also play an important role as well. With a 3.91 gear the car will move much easier out of the hole, and decrease the amount of slip. Tire size does as well, a 28" tire will require less torque to get it moving vs. a 29" tire.

So for selecting a proper converter, have your cam specs, rear-end gear ratio, and tire height available. The stall will not be an exact RPM, it will be a range within the indicated stall. I have a Circle D 3200, but it flashes to 3300.

I can't speak for the other manufacturers, because I haven't used their product, but I'd highly recommend you contact Chris Sehorn @ Circle D. He's been building torque converters for the 6L80e for quite a while now.

Your transmission will also require a tune, to set proper shift points.