Torque Converters

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eestatic

eestatic

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I'm still not quite comfortable with my knowledge in this subject area, so here is/are my scenario(s).

I have determined my cam and pistons for mild 318 build, the cam specs say "Will work w/stock converter" stall

What is the stall of a 1965 904 stock converter?

What is meant by "flash"

Also cam specs say "mild stall would benefit" cam....but stock OK...

What is "mild stall"?

My original objective (gears) was to be around 3:20-ish., but I scored a nice 8 1/4 housing with 2:71 gears in it, (upgrading the stock 7 1/4 that has 2:93? ish..)

On an E.T. slip or seat of your pants feel, a stock converter with 3:21 gears
[vs]
a mild stall with 2:71 gears would be noticeably different? How so?

Would increased stall make up any difference going the 2:71 over the 3:21 ratio?

Thanks to all who weigh in on this.!!
 
What cam?

When a converter flashes it is to the stall number.

3000 stall, when you romp on the go peddle the engine rpm's will come up to that 3000 mark and the converter will engage and launch the car.

The advantage of a higher stall is to put you in the engines/cams power band to help get the car moving instead of a sluggish take off and then getting into it.

I installed an HE268 in my teen and it was very sluggish from take off. I swapped out the 2.76 ratio to 3.55 and that helped some. I still need to install a 3200 stall converter to achieve my goal.

Your best bet is to have a converter built specifically for your combo. You will need to provide the builder with the cars weight, engine, cam spec's, rear gears,tire size AND intended usage of the car in order to get optimal performance for street driving and racing if that's what you intend to do.

Hope this helps a little.
 
X2

Also, don't be afraid of a higher stall. Just because a converter is rated to flash at 3000 doesn't mean the motor will have to rev to 3000 to move the car. A 2400 stall will work great (minimum stall for an upgrade imo) for a stock-ish build and it would drive just like stock, until you mashed the gas pedal to the floor. Higher stalls are used in stock vehicles nowadays to improve torque leaving a redlight. Believe it or not, I can brake stall my bone stock 2007 Nissan Frontier to 2500 rpm.
 
OK, lets view from a different perspective:[ Cam in the crosshairs=CRS XE268H-10 Comp Extreme energy. ]

What "Stall", [would like non-aggressive/slippage sounds at every red light!], if any, would put same performance traits to the rear wheels with 2:71 verses a 3:21 diff, if cam and power particulars are the same for both gear scenarios?
 
eestatic said:
[would like non-aggressive/slippage sounds at every red light!]
Click to expand...

This is why it is better to get your particular combo together and THEN have a converter built to suit your needs.

It's not just the cam that is considered in the stall speed, it is the entire package as I spelled out above. A properly built converter will drive normally under light throttle and it will flash when you stomp the loud pedal.

Thinking about the converter first is like putting the cart before the horse.
 
Run a stock converter. OR at the very most, a factory high stall, which is generally about 1000 RPM over stock. In reality, your combo will run better with the stock converter.

First, you need to realize that Chrysler products differ from any of the other domestic makes in this area. Stock Chrysler converters have a stall speed of around 1300-1800 RPM. The factory high stall about 1000 over that. Chrysler knew that a higher stall speed would aid in giving their cars a more snappy feel and better acceleration with highway gears.

Your engine will be very mild with the Comp 268 camshaft. Keep in mind when Comp says "Will work with stock converter but a mild stall will help" that is a blanket statement. In comparison to other makes, your STOCK converter is ALREADY a mild stall. Putting more power and torque into your engine will make the stock converter stall even a little higher. That's how converters work. The more torque they see, they higher they stall.

With your mild engine and mild 3 series gears you are talking about, IMO going to even a mild stall above the stock converter will be a mistake. You will lose some snappiness right off the line, in favor of launching at a higher RPM that's really not needed. It will do this because a higher than stock stall converter will be locked up LESS right where your engine will be wanting to pull.......just off idle. If you had 3.55-3.91 or lower gears, this effect would not exist. Also, with highway gears and a higher than stock stall (remember the 1300-1800 IS stock) your converter will not be engaged its fullest at highway speed. Converters are never fully engaged unless they are a lockup, but you will lose more engagement because of the highway gear. That will cost you fuel mileage and possibly increase heat in the transmission.

The converter stall flash is described in the MP manual like this. It can only be measured really accurately with a manual valve body, but you can get a general idea with an standard valve body. The MP book says to put the car in D (high gear with a manual valve body) apply the parking brake and hold your foot on the brake pedal. Gently depress the gas pedal until the tach STOPS rising. This is your true converter stall speed.

However, that really doesn't hold AS true as it once did, because converter technology has come light years since that information was published. It is possible with modern converter technology to get a converter that will flash to 5K RPM and still maintain good enough engagement to drive on the street. There's a down side. They are expensive. Also, you do NOT need such a converter on a street build as mild as yours. IMHO, a stock Chrysler converter is a good match for your combination up to a 3.23 gear. If you go to a 3.55, then you can step up to the factory high stall. I think if you use a stock converter you will be very happy. The converter will be RIGHT THERE at the beginning of the cam's torque curve. That's just my opinion. I am sure others will argue.
 
UOP said:
X2A 2400 stall will work great (minimum stall for an upgrade imo) for a stock-ish build.........
Click to expand...

I somewhat agree. It needs to be remembered though, that if he has a factory high stall, he's sitting right on top of 2400. Also, the stone stock converters are a good bit higher than they are given credit for. They can bump 2000 RPM fairly easily with a few upgrades.
 
New converters are easy to get 3500+ flash out of them and they drive like a stock unit around town. They do cost some $, usually around $600-700 from places like dynamic and Ultimate.

A good converter is one of the single most important piece to get great performance out of your overall driveline package.
 
eestatic said:
OK, lets view from a different perspective:[ Cam in the crosshairs=CRS XE268H-10 Comp Extreme energy. ]

What "Stall", [would like non-aggressive/slippage sounds at every red light!], if any, would put same performance traits to the rear wheels with 2:71 verses a 3:21 diff, if cam and power particulars are the same for both gear scenarios?
Click to expand...

Read the link.
 
eestatic said:
I'm still not quite comfortable with my knowledge in this subject area, so here is/are my scenario(s).

I have determined my cam and pistons for mild 318 build, the cam specs say "Will work w/stock converter" stall

What is the stall of a 1965 904 stock converter?

What is meant by "flash"

Also cam specs say "mild stall would benefit" cam....but stock OK...

What is "mild stall"?

My original objective (gears) was to be around 3:20-ish., but I scored a nice 8 1/4 housing with 2:71 gears in it, (upgrading the stock 7 1/4 that has 2:93? ish..)

On an E.T. slip or seat of your pants feel, a stock converter with 3:21 gears
[vs]
a mild stall with 2:71 gears would be noticeably different? How so?

Would increased stall make up any difference going the 2:71 over the 3:21 ratio?

Thanks to all who weigh in on this.!!
Click to expand...

What is the main use of the vehicle? Daily driver, cruiser, race car?? How much freeway driving are you going to do?
What size rear tire?

A mild stall to me would mean something no more than 22-2400 rpm.
 
RustyRatRod said:
Run a stock converter. OR at the very most, a factory high stall, which is generally about 1000 RPM over stock. In reality, your combo will run better with the stock converter.

First, you need to realize that Chrysler products differ from any of the other domestic makes in this area. Stock Chrysler converters have a stall speed of around 1300-1800 RPM. The factory high stall about 1000 over that. Chrysler knew that a higher stall speed would aid in giving their cars a more snappy feel and better acceleration with highway gears.

Your engine will be very mild with the Comp 268 camshaft. Keep in mind when Comp says "Will work with stock converter but a mild stall will help" that is a blanket statement. In comparison to other makes, your STOCK converter is ALREADY a mild stall. Putting more power and torque into your engine will make the stock converter stall even a little higher. That's how converters work. The more torque they see, they higher they stall.

With your mild engine and mild 3 series gears you are talking about, IMO going to even a mild stall above the stock converter will be a mistake. You will lose some snappiness right off the line, in favor of launching at a higher RPM that's really not needed. It will do this because a higher than stock stall converter will be locked up LESS right where your engine will be wanting to pull.......just off idle. If you had 3.55-3.91 or lower gears, this effect would not exist. Also, with highway gears and a higher than stock stall (remember the 1300-1800 IS stock) your converter will not be engaged its fullest at highway speed. Converters are never fully engaged unless they are a lockup, but you will lose more engagement because of the highway gear. That will cost you fuel mileage and possibly increase heat in the transmission.

The converter stall flash is described in the MP manual like this. It can only be measured really accurately with a manual valve body, but you can get a general idea with an standard valve body. The MP book says to put the car in D (high gear with a manual valve body) apply the parking brake and hold your foot on the brake pedal. Gently depress the gas pedal until the tach STOPS rising. This is your true converter stall speed.

However, that really doesn't hold AS true as it once did, because converter technology has come light years since that information was published. It is possible with modern converter technology to get a converter that will flash to 5K RPM and still maintain good enough engagement to drive on the street. There's a down side. They are expensive. Also, you do NOT need such a converter on a street build as mild as yours. IMHO, a stock Chrysler converter is a good match for your combination up to a 3.23 gear. If you go to a 3.55, then you can step up to the factory high stall. I think if you use a stock converter you will be very happy. The converter will be RIGHT THERE at the beginning of the cam's torque curve. That's just my opinion. I am sure others will argue.
Click to expand...

A 5000 stall on the street, hmmmm. Driving around town at say 30 miles an hour the engine is running at what, 2000-2500 rpm in high gear. So the converter is way down on its stall speed slipping like crazy and generating a ton of excessive heat (nice hot transmission oil), helps your engine use excessive 4 buck a gallon gas. Yup, nothing like an 8" converter for the street.
 
transman said:
A 5000 stall on the street, hmmmm. Driving around town at say 30 miles an hour the engine is running at what, 2000-2500 rpm in high gear. So the converter is way down on its stall speed slipping like crazy and generating a ton of excessive heat (nice hot transmission oil), helps your engine use excessive 4 buck a gallon gas. Yup, nothing like an 8" converter for the street.
Click to expand...

I didn't recommend that for him. I was making a comparison to modern converters. And yes, there are converters designed that can do that without the heat generation. Converter technology has come a long way since the 60s.
 
Kinda a bunch of funny stuff. You will run quicker with the right converter. That's a fact. No a stock converter will not be as quick as a good converter. I've replaced the factory Hi stall junk with very tame PTC converters and picked up .4 without any drivability issues. I could have gone for a race converter and seen more gain but I drove up to 120miles to the track and wanted a mild converter. Run from a factory converter if you want performance. Period.
 
RustyRatRod said:
I didn't recommend that for him. I was making a comparison to modern converters. And yes, there are converters designed that can do that without the heat generation. Converter technology has come a long way since the 60s.
Click to expand...

I know, I worked in the industry for almost 30 years.
 
Ok boys, put your wee-wee's and tape measures away. This isn't about you. :D
 
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