455 stall speed

Apologies if this is beating a dead horse, but I don't see much for bone stock engines discussed. Would there be any advantage to a higher-than-stock stall torque converter on a stock SF code 455? My usual logic would say yeah throw a 3,000 stall in there and go for it, but I worry that might actually be too much. This engine is a first for me in all regards, particularly willingness to move a house starting at about 1400 rpm. What say the experienced lads (and lasses)?

 

What RPM does the torque peak in your powerband?

Get a converter that takes advantage of that peak.

 

X2 on what Larry said. I have one of Jim's 9.5" in my big Riv and I love it!

 

Give Jim Weise a call.
Don't even consider an "off the shelf" convertor

 

Yes, there is.

There are 3 advantages, even in a dead stock vehicle, with no other mods needed.

1. More torque muliplication... the stock 13" TH 400 converter has a Stall torque ratio of around 1.2... my average converter build is closer to 2.0-1. Many customers report it's like they added 50 foot lbs of torque to the car, and in reality, they did.

2. Less rotating weight- The stock converter, with oil, weights 47 lbs... my 9.5" weights 29... Lighter weight on the back of the crank makes a big difference on how fast the engine can accelerate in rpm.

3. Allows the engine to reach the power band sooner.-- This is the traditional advantage of a high stall converter. The stock engine has a torque peak of 2800 to 3200 rpm, not the 1300rpm of your stock converter.

In the past, professionals and experienced enthusiast frowned on the high stall converter being your first mod, but only suggested it after long duration cams and big manifolds had raised the torque peak, to a point were the car was a slug at low speeds. This was because the traditional 11"-12" performance converters, made from the large shells, had significant downsides. Because internal oil flow in the converter had to be manipulated to create inefficiency, which in turn allowed the engine to rev against it without moving the car (stall speed).

There were two big problems with that approach. First off, it creates excessive heat, in normal driving. And secondly, it produces the dreaded "muddy" feeling in the throttle pedal.

Those issues are a thing of the past with this new generation of performance converters. The stall speed comes from the simple inability of the force of the fluid, to move the weight of the vehicle, because there is so little fluid in it, compared to the big old style 12 and 13 inch units.

With the correct selection of stator, pump, and mods/end plays, what we get is a unit that stalls at or near your torque peak, at WOT with traction, yet at part throttle, feels nice and tight, like that big old stocker did.

One of the first tests I am going to do, when I get time to put the shop test car together, is to replace nothing but the converter. I suspect that the car will decrease it's 1/4 mile times nearly half a second... I have had many reports of near stock vehicles doing just that, and 2-3 tenths off in modified GS's, when replacing old style "High stall" converters.

The latest generation of performance torque converter is by far the best bang for the buck. There is not much (if anything) you can do for less than $700, and improve performance, and all around driveablity, as much as one of my new converters will.

JW

 

Replacing your 2.29 gears will make a huge difference; plus the 7.5 rear isn’t long for this world behind a 455.
Patrick

 

I bought an 8.5 from a board member that's going in when I get the time, with either 3.23 or 3.42 gears. Every time I drive it and make it home is a surprise to me, it has a mini spool in it.

Jim, do you think it's best to stall right there at the torque peak?

 

Me too. Love it. I added Jim’s converter and 2.5” mandrel exhaust. Picked up 0.5 second (Combined) with those two improvements on a basically stock motor.

I have 3.31 gears.... wish I would have went 3.42 For the track. I only drive the car around town and at the track.

 

Thanks for the advice guys! I got my headers today, the rear end is next and then when that's ready I'll have to get in touch with Jim about converters.

 

Question: I had my 1971 Riviera's TH400 converted to "Switch Pitch", manually controlled by cabin-located switch. We used parts from a donor '67 Delta 88 TH400. I also have a "Variable Vane" converter from a ST300. Would it be worthwhile to give the ST300 converter a try? Here's some info from Wikipedia:

"From 1964-1967, Buick and Oldsmobile versions of this transmission used a torque converter with a variable-pitch stator called Switch-Pitch by Buick and Variable Vane by Olds. The stator blades moved from high to low position by an electrical solenoid and a stator valve, controlled by a switch on the throttle linkage. At light to medium throttle, the stator blades were at 32°, providing a torque multiplication of 1.8:1 and a converter stall speed of approximately 1800 rpm. At ⅔ to full throttle, the blades switched to the 51° high position, giving torque multiplication of 2.45:1 and a stall speed of approximately 2300 rpm. The blades were also set to the high position at idle to limit creep when stopped in Drive. The variable-pitch stator was eliminated after 1967. This feature was not used on the Pontiac versions of this transmission."

 

My Riv = 9.5:1 CR, 350 Hp/495 Tq (chassis dyno), 2.93 posi rear, WOT shifts at 5300rpm

 

Sort answer: maybe. The ST300 converter is an inch smaller diameter, and will likely stall I dunno - 300-400 rpm higher? For your combination and those gears ,it may make a noticeable difference, as it'll let the engine rev where the rear ratio wont....