Stall speed
Thread Starter
Safety Car
Joined: Jan 2008
Posts: 3,791
Likes: 428
From: Aarhus, Denmark
Stall speed
Hi,
I have a friend that has a 1971 Corvette, he would like to have a new converter.
Today he has 3.08 rear, but maybe it will be 3.70 soon.
Can anyone tell me what stall speed would be correct for him? (stall speed if he goes for 3.08 and if he goes for 3.70)
The car is a street fighter, 0-60 mph car, not 1/4 mile/race car.
New 383 engine.
AFR 195
EZ-EFI 1.0
Comp Cams 12 466 8
1.6 rocker arms
G-team 7530 intake
Headers and 2½" exhaust
TH400 transmission, with shift kit installed.
3.08 OR 3.70 rear
255-60-15 tyre
Thx,
John
I have a friend that has a 1971 Corvette, he would like to have a new converter.
Today he has 3.08 rear, but maybe it will be 3.70 soon.
Can anyone tell me what stall speed would be correct for him? (stall speed if he goes for 3.08 and if he goes for 3.70)
The car is a street fighter, 0-60 mph car, not 1/4 mile/race car.
New 383 engine.
AFR 195
EZ-EFI 1.0
Comp Cams 12 466 8
1.6 rocker arms
G-team 7530 intake
Headers and 2½" exhaust
TH400 transmission, with shift kit installed.
3.08 OR 3.70 rear
255-60-15 tyre
Thx,
John
Safety Car
Joined: Oct 2004
Posts: 3,921
Likes: 731
From: Youngstown Ohio
If the only change is the rear gear ratio, there is no reason to change the stall speed converter. The converter should be changed to match the engine characteristics......specifically, the cam. Some cams require a higher stall speed to keep the engine's RPMs OK at idle, especially a street car.
You list a performance cam with your specs........Comp Cams specs that cam as 1800-5800 rpm range, their largest recommended for a stock converter. A 2500 rpm converter will give you more "zip" out the hole and will probably be more fun than stock, but is not mandatory regardless of which rear gears you choose.
You list a performance cam with your specs........Comp Cams specs that cam as 1800-5800 rpm range, their largest recommended for a stock converter. A 2500 rpm converter will give you more "zip" out the hole and will probably be more fun than stock, but is not mandatory regardless of which rear gears you choose.
Last edited by C3 Stroker; Jan 4, 2018 at 04:37 PM.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
And the higher stall converter will generate more heat, making trans temperature a factor- as in a temp gauge, bigger trans cooler and more frequent fluid changes.
You can pickup a little bit by putting a converter from a TH350 equipped car in that TH400..
You can pickup a little bit by putting a converter from a TH350 equipped car in that TH400..
Le Mans Master
Joined: Feb 1999
Posts: 8,351
Likes: 75
From: Tampa Bay FL
Agree. Unless the new cam says higher stall, the stock 2000rpm converter in your vette will launch hard. It will even like the better gears. Save yourself the added heat unless you need an even harder launch. But, you may have more breakage (half shafts, diff, etc.) to consider if you boost stall speed above 2000rpm.
I run 2000rpm stall with 700R4, retro roller cam, 3.54 gears in my warmed over L48 (haven't installed the 4-bolt yet). It launches HARD (good) from a dead stop and runs like a scalded dog. Barks/spins thru 1-2 shift too.
I run 2000rpm stall with 700R4, retro roller cam, 3.54 gears in my warmed over L48 (haven't installed the 4-bolt yet). It launches HARD (good) from a dead stop and runs like a scalded dog. Barks/spins thru 1-2 shift too.
Thread Starter
Safety Car
Joined: Jan 2008
Posts: 3,791
Likes: 428
From: Aarhus, Denmark
Thx all.
So you are saying 2000 would be fine, but he can go to 2500, but it make a bit more heat = add a cooler.
The converter he has today is the factory 71 converter.
If he decides to go for the 2000 stall speed, will it then be better to buy a new modern 10" with 2000 compared to the factory 71?
If yes, what will he gain?
I tought the factory stall speed was 1400 or 1600, but it's 2000?
So you are saying 2000 would be fine, but he can go to 2500, but it make a bit more heat = add a cooler.
The converter he has today is the factory 71 converter.
If he decides to go for the 2000 stall speed, will it then be better to buy a new modern 10" with 2000 compared to the factory 71?
If yes, what will he gain?
I tought the factory stall speed was 1400 or 1600, but it's 2000?
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
Thx all.
So you are saying 2000 would be fine, but he can go to 2500, but it make a bit more heat = add a cooler.
The converter he has today is the factory 71 converter.
If he decides to go for the 2000 stall speed, will it then be better to buy a new modern 10" with 2000 compared to the factory 71?
If yes, what will he gain?
I tought the factory stall speed was 1400 or 1600, but it's 2000?
So you are saying 2000 would be fine, but he can go to 2500, but it make a bit more heat = add a cooler.
The converter he has today is the factory 71 converter.
If he decides to go for the 2000 stall speed, will it then be better to buy a new modern 10" with 2000 compared to the factory 71?
If yes, what will he gain?
I tought the factory stall speed was 1400 or 1600, but it's 2000?
And if you were to go to all the trouble of pulling the convertor, I sure wouldn't buy & install a different GM unit just to save a few bucks over after-market.
Last edited by HeadsU.P.; Jan 4, 2018 at 06:20 PM.
Thread Starter
Safety Car
Joined: Jan 2008
Posts: 3,791
Likes: 428
From: Aarhus, Denmark
So he is in there anyway.
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Melting Slicks
Joined: Oct 2008
Posts: 2,154
Likes: 69
From: Regina Sk Canada
More torque will make a converter flash higher. In my 80 vette, i have a stock lock up converter the local tranny shop reworked to stall at around 2000 rpm. I have an external trans cooler just to keep the trans heat out of the rad.
My duster i have a 10" TCI 3500 stall flashes to 4000 drives fine on the street doesn make any more heat. Once to get into the 8-9 " inch units 4500 stall and up you need to worry about heat.
I had a Coan glide in my 77 BBC Camaro with a 5000 stall and a brake. After a couple passes the trans temp got warm, but not overtemp. I had a gauge tapped into the pan. drove that on the street with no issues.
My duster i have a 10" TCI 3500 stall flashes to 4000 drives fine on the street doesn make any more heat. Once to get into the 8-9 " inch units 4500 stall and up you need to worry about heat.
I had a Coan glide in my 77 BBC Camaro with a 5000 stall and a brake. After a couple passes the trans temp got warm, but not overtemp. I had a gauge tapped into the pan. drove that on the street with no issues.
Le Mans Master
Joined: Oct 2010
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From: melbourne florida
2023 C3 of the Year Finalist - Modified
I run a 9.5 in 2800 Stahl with 3:55 gears it takes drag radials to keep from destroying the tires. The smaller diameter cuts rotating mass and the engine revs quicker making just driving around snappier. Just more to consider
Le Mans Master
Joined: May 2002
Posts: 5,084
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From: Lebanon Township New Jersey
This is an often overlooked advantage of higher stall speed converters, with smaller diameter and much less weight.
Race Director
Joined: May 2005
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From: Millington Illinois
St. Jude Donor '08-'09
TH400 trans in Corvettes was a 2000 stall factory. Other uses were lower stall. That cam is an 1800-5800 cam in a 350. In a 383 drop that 300 RPM at least. I would not touch the convertor. A TH 400 with a shift kit and that engine will be a beast with the 3.08. It will be noticeably better with the 3.70
Last edited by 63mako; Jan 4, 2018 at 08:26 PM.
Safety Car
Joined: Oct 2004
Posts: 3,921
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From: Youngstown Ohio
I used a 2500 rpm 10'' TCI in my 383 before eventually a custom Art Carr 3000 w/4300 flash. The 2500 was great on the street and drove like stock. It enabled the engine to idle without surging, and gave me a great holeshot. I did install a trans cooler. You may not have problems, but heat will increase if only a little. I'd recommend a cooler with any converter upgrade from stock.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
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From: Hermosa
Couple of reasons for a higher stall as a street motor.
One is to get the engine farther up in the rpm range where it’s developing more torque for more power to the wheels.
Second is to allow an engine with a large cam to idle.
Neither of these seems to be an issue with the cam spec’d for this engine.
I would say the cam is relatively short for a 383 so it will develope lots of torque down low. DCR should be computed to see how high it’s gonna be based on the CR so as to not have issues with detonation.
It should also idle very easily and not require a higher stall converter.
One is to get the engine farther up in the rpm range where it’s developing more torque for more power to the wheels.
Second is to allow an engine with a large cam to idle.
Neither of these seems to be an issue with the cam spec’d for this engine.
I would say the cam is relatively short for a 383 so it will develope lots of torque down low. DCR should be computed to see how high it’s gonna be based on the CR so as to not have issues with detonation.
It should also idle very easily and not require a higher stall converter.
Thread Starter
Safety Car
Joined: Jan 2008
Posts: 3,791
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From: Aarhus, Denmark
Couple of reasons for a higher stall as a street motor.
One is to get the engine farther up in the rpm range where it’s developing more torque for more power to the wheels.
Second is to allow an engine with a large cam to idle.
Neither of these seems to be an issue with the cam spec’d for this engine.
I would say the cam is relatively short for a 383 so it will develope lots of torque down low. DCR should be computed to see how high it’s gonna be based on the CR so as to not have issues with detonation.
It should also idle very easily and not require a higher stall converter.
One is to get the engine farther up in the rpm range where it’s developing more torque for more power to the wheels.
Second is to allow an engine with a large cam to idle.
Neither of these seems to be an issue with the cam spec’d for this engine.
I would say the cam is relatively short for a 383 so it will develope lots of torque down low. DCR should be computed to see how high it’s gonna be based on the CR so as to not have issues with detonation.
It should also idle very easily and not require a higher stall converter.
Dyno says (again with 1094):
Le Mans Master
Joined: Apr 2011
Posts: 6,284
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From: Hermosa
Less slippage better more rugged construction.
A torque converter of the 70's is likely less efficient (more slippage) and may not be able to handle the torque developed by the new engine.
A new torque converter should be furnace brazed, have a anti-balloon plate or at least a larger hub center and will handle the torque of the new engine.
Your current 2000 stall converter may not stall until 2800 with the 383. Stall depends on the torque developed by the engine.
Personally I would not use a stock unit on a much higher powered 383.
Last edited by REELAV8R; Jan 5, 2018 at 10:00 AM.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
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From: Hermosa
Lots of torque to spare down low peaks near 3500 and starts falling off at 4500. HP starts falling at about 5500.
So it could use a longer duration cam or a narrower LSA if a guy wanted and get the torque peak around 4200 or so. Allowing the HP to climb all the way to 6000 to 6200.
Just my personal preference really. I feel one of the advantages of greater displacement is being able to run a bigger cam and not lose the bottom end in the process vs a smaller displacement.
DCR looks good as long as aluminum heads are used.
I'm running 8.8 DCR but at 3500 to 5500 feet and have no issues with detonation even on 87 to 88 octane.
So it could use a longer duration cam or a narrower LSA if a guy wanted and get the torque peak around 4200 or so. Allowing the HP to climb all the way to 6000 to 6200.
Just my personal preference really. I feel one of the advantages of greater displacement is being able to run a bigger cam and not lose the bottom end in the process vs a smaller displacement.
DCR looks good as long as aluminum heads are used.
I'm running 8.8 DCR but at 3500 to 5500 feet and have no issues with detonation even on 87 to 88 octane.
Last edited by REELAV8R; Jan 5, 2018 at 10:29 AM.
