<VV> PG stall & musings on speed

[Tony Underwood]

At 06:29 hours 04/29/2006, Padgett wrote:

>>Frequently mentioned are the "stall" characteristics of the 
>>converters. The idiot question is just what is it that's happening 
>>when the torque converter stalls?


I might step up and mention that definition of terms here is gonna be 
helpful; I keep hearing people talk about getting a "stall" 
converter.   This is sorta like calling every refrigerator a Frigidaire.

One outfit that became known for making a decent converter for 
performance applications was Stahl...  and ever since, people who 
talked about getting a Stahl converter confused the others who 
thought a Stahl converter automatically meant a high stall 
speed.   They even called the trick converters "high stahl"... as 
well as also referring to those trick converters as "stall converters".


There are torque converters which were manufactured by Stahl, and 
there are high stall converters manufactured and/or modified by a 
bunch of other outfits.   (what ever happened to Stahl anyway?)

When you say you're gonna get a Stahl converter, be sure you know 
what you're actually talking about when what you want is a higher 
stall speed converter.   Now back to the lesson:


>First the stall speed (sometimes called "flash") is the rpm an 
>engine will reach with a transmission having a torque converter when 
>the accelerator is floored in gear with all brakes set hard (see "line-lock")
>
>A "tight" converter will reach around 1700 rpm. This is typical of 
>automatics before lockup was common such as the Corvair. A "loose" 
>converter will rev higher. My 88 3800 with a lockup transmission 
>will flash to 2600 rpm.


Stall speed is very dependent upon the size of the engine in front of 
it.    A converter that stalls at 2000 rpm behind a stock mild engine 
could well stall at over 3000 rpm when loaded up against a tweaked bigblock.


>For drag racing you want the stall speed to be near the torque peak 
>of the engine and may be well over 3000 rpm.

There are converters available with stall speeds approaching 5000 rpm 
for those hysterical maniacal smallblock engines in dragracing that 
will twist up past 10,000 rpm.  Such a converter would be rather 
small in diameter and beefed up accordingly to handle the stress it's 
gonna suffer in race conditions.   Some of these race converters have 
to transmit as much as 1000 hp or more.


>Back in the day it was common to see 9" (very small) Vega torque 
>converters behind big inch engines to reach a high stall speed.

They suffered for it too.   These Vega converters allowed a radical 
bigblock Chevy to stall at 5000 rpm while waiting for the tree to 
drop Green.   Now, think about that for a moment.   The converter was 
absorbing the full output of a bigblock Chevy race engine for as long 
as the driver stood on the throttle until the tree went 
Green.   Consider around 740 watts of heat per horsepower if you 
wanna think that way.    Then figure a 427 making around 500 hp (mild 
dragrace engine) loading up against that little Vega 
converter.    It's no small wonder that a lot of dragracers wasted a 
LOT of Vega converters until the folks in aftermarket like B&M and 
Stahl etc started making some serious torque converters that wouldn't 
rip their own insides apart after three runs.

It's interesting to remember that *good* performance-slanted 
efficient torque converters haven't been around that long.


>It is not good to hold an engine at stall as all of the energy of 
>the floored engine is going to be absorbed by the torque converter 
>and turned into heat. Racing transmissions will have big coolers to 
>help keep the temperature within limits during staging.


The typical SS/AA race engine will churn against the converter hard 
enough to raise the temp of the ATF from ambient to over 300 degrees 
in about 5 seconds.   Not even a glorified space-age cooler will help 
cool the fluid under such a loading.    However, that loaded up 
converter would launch a Barracuda from a standing start to 60 mph in 
less than 2 seconds, on its back wheels only, the whole way to 
60.    You can only imagine how hot the transmission would be by the 
time the car hit the lights 1320 ft later (at 150 mph).


>As the benefits of automatics in drag racing became evident there 
>were several attempts to meld the best characteristics of both a 
>manual and an automatic transmission and things like slider clutches 
>and "clutch-flytes" became common.

...another attempt to get around the slippage of converters of the 
times.    The 727 Torqueflite was a popular automatic in those days 
with dragracers, even those not running Chrysler race cars.   Later 
on, in some of the lighter cars with very large engines, Powerglides 
with a clutch began getting popular.   Only two speeds were needed 
with light weight and very strong "torky" engines.

It helped develop a definite shortage of Powerglide transmissions.   ;)


>The best thing about the automatics was that the eye/hand/foot 
>(really *ss/hand/foot) coordination required to get a big-inch car 
>off the line without "going up in smoke" was greatly simplified and 
>the demand for people with three feet was reduced. Someone who was 
>good with a Muncie could launch balancing the need for weight 
>transfer to the back with holding the engine at it peak by burning 
>the clutch for the first 20 feet and never touch the clutch for the 
>rest of the run (grinding every other tooth off the synchro rings helped).

"Joe Liberty" and his slik-shifted transmissions made crashboxes 
respectable again.   Lots of dragracers were running the whole race 
without touching the clutch pedal after launching.

You had to be good; miss a shift and you could clean out the insides 
of the gearbox if you had some serious horsepower.


>Something that is hard to imagine in these days of Barrett-Jackson 
>cars is just what it took to be a successful racer. Things broke. Often.

Again, miss a shift and Bang went the engine.   Not much in the order 
of rev limiters Back When... what limited the engines ability to rev 
was often just the valve springs.   Fierce springs, miss a shift, 
engine rpm shot to the moon, rod shot through the oilpan.    Lots of 
dragracers started looking into serious automatic transmission mods 
for race cars.    In spite of the claims by some that automatic 
transmissions would never outrun their manual counterparts, it took 
little time before tech overtook tradition and automatics began 
setting records.

Currently the record for the fastest door-slammer stock class in 
dragracing is held by a 1968 Plymouth Barracuda with an automatic 
transmission, 8.55 seconds @ 155 mph in the quarter.


>Explosion-proof bellhousings had to be a rule because clutches 
>exploded but the protection added weight.


Yep...  sometimes called "blastcans", the scattershields actually 
weren't that much heavier than their aluminum counterparts (made of 
hot-formed rolled steel plate) and actually lighter than the cast 
iron-only bellhousings offered on some engines.

Even in the case of the blastcan replacing a lighter bellhousing, it 
only took one clutch explosion tearing the dashboard in half and 
shattering the windshield to convince people to count their toes (or 
feet, depending) and spring for the steel aftermarket 
bellhousing...  which also offered several different bolt-hole 
patterns which allowed the option of using several different types of 
transmissions.      Ford toploaders and Chrysler A833's were popular 
transmission swaps for GM sorts who wanted a gearbox that wouldn't 
split the case on launch.    As good as it was, the Muncie 4-speed 
(including the M22) simply wouldn't hold up well for very long behind 
a big engine in a heavy car with some serious tires on back.    The 
Mopar and Ford gearboxes may have been heavy but they didn't break.


>Someone *really* good could make a Muncie or even a Saginaw "sound 
>like an automatic" and get a jump from flywheel inertia from every 
>shift. The shift rods used by an aftermarket Hurst shifter were 
>considerably larger diameter than those from the factory for one 
>very good reason: the factory rods bent under drag racing pressure 
>(accepted technique for shifting from first to second was as the 
>engine neared the shift point (see *ss above) you pulled back as 
>hard as you could on the T-handle (you could exert more force with a 
>T-handle than a ball knob) and either (racer's choice) bat the 
>clutch (and hope it did not stay on the floor)


Or trash the diaphragm clutch to begin with and use a B&B clutch plate.


>or pop back once on the gas and get right back on it hard. (Warren 
>used to get on me about "rattling the floorboards").

This only worked with a gearbox that had been "Clicked".    Once you 
got the hang of it and practiced a while (usually busting a gearbox 
or two in the process) you could indeed shift a "clicked" 4-speed so 
quickly it sounded like an automatic.    Just "blip" the throttle off 
for a moment and slam the shift lever into the next gear and then 
nail it again, all in a blipyanknailit cycle lasting ~1/8 
second.    Anyone who ever saw Ronnie Sox shift a big heavy Chrysler 
4-speed like an automatic will know what I mean.



Speaking of whom:   Ronnie Sox, RIP, last week, lost his bout with 
cancer, a legend lost to us all.



>Brutal but worth a fraction of a second on every shift at a time 
>when fractions decided races.

...it still does.   ;)


>Nowadays I have become kindlier/gentler partly because back then a 
>clutch change was no further away that a tree with a big root or a 
>tall curb.

Use the B&B style clutch and you wouldn't have to change it.   Can't 
say that about the gearboxes though.  ;)



tony..