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Discussion Starter · #1 · (Edited)
I,m looking at getting a new converter from FTI,. Looking at these converters trying to decide on which one.
1. 2400-2600 stall. 9.5".
2. 2800-3000 stall. 9.5".
3. 2600-2800 stall 9.5" I,m thinking this one.
4. 2400-2600 stall 12"
Car. Setup is 2dr 56 Chevy.
3:73 rear gear.
700r4 trans.
2000 L31 vortec 350.
Lunati cam 2008130
Adv dur 278/288
Dur. @ .050 219/229
lift .503/.503
1800-5800
Heads are modified for .550 lift.



Full headers.
670 street avenger carb.
Edelbrock rpm intake.
Car has a 2100 stall converter now. A nd is sluggish from the line. Need a higher stall converter but not sure how much more.
 

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Choice 2 or 3 will work fine. 2 probably a little bit more street and quarter mile. 3 a bit more slip will be fine on the street and a bit better for eight mile drags.

Dont forget to add cooling these small diameter converters when operating hard in the stall range get hot that on top of these overdrive trannies like the 700R4 like to cook their ATF without any help from a high stall converter.

You can fiddle the stall with different weights of ATF, but that takes digging deeper in the subject than the parts store shelf brands.

Bogie
 

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You've got a real mix of stuff there. Another street car that wants to be a drag racer. I would work on the timing and timing curve first then tune that carb/intake combo. Some lash work with the cam and/or advancing the cam a bit should help too. There's a lot you could do before putting another converter in it. And it would be cheaper to send your converter in and have it upped in stall speed than to purchase a new one.

Crap, I'm going to edit this thing 5 times before I'm finished.

One of things you should understand too is that "converter stall" numbers provided by a company, even a really good one like FTI are nothing but estimates. They have no idea of what the torque level is going to be that their converter is put behind. You say your current converter is 2100, please tell me how you tested it for that number or is that the number that was provided when you purchased it? If the latter is the case, then you really don't know what your converter is currently flashing at and that is a number that you need. You also didn't mention what rear tire you're running or the weight of the vehicle. All of which can have a bearing on how the torque of the engine is handled through the converter to get the car moving.

Then I see you have this posted on clubhotrod.com too. And you got this answer which is a bit more elaborate but in the same ballpark as mine:

Assuming that the present converter is operational to slip to 2100 (as designed), it should do a pretty good job of moving your heap off the line. Your final drive ratio is 11.41:1 in first gear (3.06 X 3.73), twisting through a 27" tire (with a modicum of engine torque, you should be close to getting some daylight under the left front tire on launch). You may not realize it, but the looser you go on the converter, the farther away you move the car from being streetable and you may just as well begin yanking out the extra seats, bumpers, bumper braces, etc., etc. as well as moving the battery to the extreme right rear of the car, using #2 welding cable from the trunk to the engine bay. Drill a hole in the bumper to mount a good quality master on-off switch (required by drag rules when you remount the battery anywhere other than the stock location. In my opinion, you have a great, streetable combination now, and going looser on the converter will only wreck that.

I'm going to change lanes and suggest that you make other changes to produce additional engine torque before you opt for the looser converter. You may or may not be familiar with ported vacuum versus manifold vacuum. Ported is vacuum taken from ABOVE the throttle plate. Manifold is vacuum taken from BELOW the throttle plate. All of us old guys are familiar with using manifold vacuum because that's the only type that was available to us before the advent of the Federal Government forcing auto manufacturers to clean up their act, beginning in 1967.

What I have in mind for you is a DUI (Davis Unified Ignition) distributor, together with the best plug wires money can buy and routing them away from each other by at least a full inch from the cap to the plugs, using standoffs and/or separators that will not conduct electricity. You will provide all the facts and figures about your combination and the engineers at Performance Distributors in Memphis will dial in your new distributor before shipping it to you. YOWZA, YOWZA. (901) 396-5782. I strongly recommend purchasing direct, not through a speed shop.


He makes some good points here and I think we both are pushing the same idea. People put together combinations with some expected results and when said results do not come about - people decide that there must be something slightly amiss in the combination that we so carefully crafted. If you do this long enough, you find out that ordering parts A,B and C out of the catalog will not guarantee the result, but ordering those parts and fine tuning not only will probably get you there, it might even be a bit better. That's what this game is all about.
 

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That DUI distributor will work good. I have one in my 406.
I can also speak for a 9.5 inch FTI 3000 stall with lockup for the 700r4.
I had almost the exact L31 as you, it worked very well. I picked up nearly half of a second in the 1/4, and had to run drag radials on the street. That's how much just the converter woke it up.
When I sold the Vortec, and put the trusty, blue old original 350 back in, it drove as if there was a totally stock torque converter in it. So much, I was worried. But 3 months later when I installed the 406, BAM! It started behaving like a performance trans again. It flashes about 3500 now when I lean on the loud pedal, but normal driving you can't tell its there.
You have made a good decision on getting a custom converter, now the question is which one?
I went a little higher, and am not disappointed at all. My truck weighs right under 4000 pounds, with a 3.90 gear.
As was mentioned above, if you can drop a couple hundred pounds you will be amazed. I have dropped about 300 so far, but the truck had lots of easy trimmings to lose...
 

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I would try #2 converter... From your list of converters, I take it you think the RPM numbers for stall are hard factual numbers. They are not. Likely your actual RPM number in stall will be lower.
 

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I would try #2 converter... From your list of converters, I take it you think the RPM numbers for stall are hard factual numbers. They are not. Likely your actual RPM number in stall will be lower.
Yes, forgot to mention. Sitting at the light with my foot on the brake, my truck tries to move through the beams at about 2600 rpm. But once you launch, its a whole nother story!

Random thought.
Is nother even a word???
 

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Discussion Starter · #11 ·
Choice 2 or 3 will work fine. 2 probably a little bit more street and quarter mile. 3 a bit more slip will be fine on the street and a bit better for eight mile drags.

Dont forget to add cooling these small diameter converters when operating hard in the stall range get hot that on top of these overdrive trannies like the 700R4 like to cook their ATF without any help from a high stall converter.

You can fiddle the stall with different weights of ATF, but that takes digging deeper in the subject than the parts store shelf brands.

Bogie
Thanks Bogie for your input, already have external cooler on the trans.
 

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Discussion Starter · #12 ·
That DUI distributor will work good. I have one in my 406.
I can also speak for a 9.5 inch FTI 3000 stall with lockup for the 700r4.
I had almost the exact L31 as you, it worked very well. I picked up nearly half of a second in the 1/4, and had to run drag radials on the street. That's how much just the converter woke it up.
When I sold the Vortec, and put the trusty, blue old original 350 back in, it drove as if there was a totally stock torque converter in it. So much, I was worried. But 3 months later when I installed the 406, BAM! It started behaving like a performance trans again. It flashes about 3500 now when I lean on the loud pedal, but normal driving you can't tell its there.
You have made a good decision on getting a custom converter, now the question is which one?
I went a little higher, and am not disappointed at all. My truck weighs right under 4000 pounds, with a 3.90 gear.
As was mentioned above, if you can drop a couple hundred pounds you will be amazed. I have dropped about 300 so far, but the truck had lots of easy trimmings to lose...
Well EA your truck setup is pretty comparable, thanks for sharing that. More to think about. And i have nowhere to get rid of couple hundred pounds.
 

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Discussion Starter · #13 ·
I would try #2 converter... From your list of converters, I take it you think the RPM numbers for stall are hard factual numbers. They are not. Likely your actual RPM number in stall will be lower.
Crosley, i know the numbers they put on converters are not set in stone. I know it depends some different factors with the cars setup. But just looking for other peoples experiences with hotrods, torque converters. Thanks for the vote on #2. I'm still thinking #3 street car daily driver only.
 

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Crosley, i know the numbers they put on converters are not set in stone. I know it depends some different factors with the cars setup. But just looking for other peoples experiences with hotrods, torque converters. Thanks for the vote on #2. I'm still thinking #3 street car daily driver only.
You have a couple of relies at CHR
 

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Thanks Eric for your opinion, i was thinking that stall rpm might be a little high for my daily driver street car. If that even makes a difference?
#3 would be my second choice, followed by #1.....with #4 a very distant last place. Actually wouldn't even make my list.

The biggest improvement you are making is going to the smaller diameter....that's where all the benefits are.
Only once you've experienced running a "tight" smaller diameter converter versus a "loose" 12" stock diameter converter will you really know what I'm getting at.
Even if both are rated at the same stall speed, there is a world of difference in how they act.
It'll act mostly normal until you put your foot down, then it will wake right up.
 

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So why is the diameter that important? Won't a 9.5" 2400-2600 stall converter perform about the same as a 12"? I know the 12" holds more fluid and will be heavier when full, but once up to speed the extra weight should help... though it will take a slightly longer amount of time to get up to speed. If you're standing on the brake and bringing the engine up near the stall speed before letting off the brake and taking off, that slightly longer up-to-speed time (less than 1 second?) shouldn't make a difference. That larger diameter and higher volume of fluid should cool better too.
 

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In order to get the higher stall speed from the bigger converter, fin angles have to be different, and internal clearances have to be different.

As a general rule, the larger the converter diameter, the lower the potential stall speed range that can be built on that core.....for example you can't build a 4000 rpm stall 12" converter, it will be so loose and sloppy and inefficient that you'll think you've got a go-cart centrifugal slipper clutch in there.
By the same token, trying to get a 1200 rpm stall towing converter built on an 8" core will result in slippage bwcause you just cannot build it with stall that low, power transfer will just shear the fluid and make heat.

Fin counts and blade angles will be vastly different.
Torque multiplication at stall will be a lot different too.
Capacity of fluid is on no real value for cooling purposes, fluid is continually pump through the converter to cool it and keep it full.

A lot of the converter industry has gone to using the 245mm GM core as it has the most available options for different blade angles and fin counts....this video below may help you makes some sense of it.

Generally, trying to raise the stall speed of a large diameter for performance use just makes in worse. It will get outperformed by a correctly built smaller diameter converter every time if we are talking street performance use or race.

What Is Stall Speed? - Episode 5 - Hughes Performance
(5) Ep. 5 Torque Converters 101: What Is Stall Speed? - YouTube

Stator Design, Construction, and Function - Episode 4 - Hughes Performance
 

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In order to get the higher stall speed from the bigger converter, fin angles have to be different, and internal clearances have to be different.

As a general rule, the larger the converter diameter, the lower the potential stall speed range that can be built on that core.....for example you can't build a 4000 rpm stall 12" converter, it will be so loose and sloppy and inefficient that you'll think you've got a go-cart centrifugal slipper clutch in there.
By the same token, trying to get a 1200 rpm stall towing converter built on an 8" core will result in slippage bwcause you just cannot build it with stall that low, power transfer will just shear the fluid and make heat.

Fin counts and blade angles will be vastly different.
Torque multiplication at stall will be a lot different too.
Capacity of fluid is on no real value for cooling purposes, fluid is continually pump through the converter to cool it and keep it full.

A lot of the converter industry has gone to using the 245mm GM core as it has the most available options for different blade angles and fin counts....this video below may help you makes some sense of it.

Generally, trying to raise the stall speed of a large diameter for performance use just makes in worse. It will get outperformed by a correctly built smaller diameter converter every time if we are talking street performance use or race.

What Is Stall Speed? - Episode 5 - Hughes Performance
(5) Ep. 5 Torque Converters 101: What Is Stall Speed? - YouTube

Stator Design, Construction, and Function - Episode 4 - Hughes Performance
This is a nicely put, easily understood analogy! I had a 3k stall 12" in my S-truck and hated it. Ended up with a 3.4k stall 9.5" that cut a half second off the 0-60 time, 1.3 off the quarter, yet drove much nicer around town. The only obvious difference between it and a stocker was the lack of "pull" while stopped at a light. You could remove your foot off the brake without any creep.

Russ
 
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