#1  
Old 10-06-2021, 05:50 PM
Rar_421 Rar_421 is offline
Junior Member
 
Join Date: Mar 2021
Posts: 14
Default Stall rpn vs cruise rpm

What's the rule of thumb on how much higher your cruise rpm should be over stated stall Rpm? Heard every thing from 100 Rpm to 500 Rpm

  #2  
Old 10-06-2021, 06:55 PM
steve25's Avatar
steve25 steve25 is online now
Ultimate Warrior
 
Join Date: May 2008
Location: Westchester NY
Posts: 12,892
Default

A lot depends on your cars rear gear ratio and how much excess torque your motor makes to sustain a given mph on level ground.

What cid motor are we talking about here?

__________________
You can cut out a man's Tongue from his Mouth, but that does not mean hes a liar , it only shows that you fear the truth he might speak about you!

Wernher Von Braun warned before his retirement from NASA back in 1972, said that the next world war would be against the ETs!
And he was not talking about 1/8 or 1/4 mile ETs!
  #3  
Old 10-06-2021, 07:02 PM
Rar_421 Rar_421 is offline
Junior Member
 
Join Date: Mar 2021
Posts: 14
Default

350,17 heads, removed the st300 and rebuilt a th350 and found a deal on a Hughes 2000 stall,I have to determine my gear ratio when I can get to garage this weekend,but it's likely it has the standard 2.56 ratio,had planned on 3.36 gears this summer but work got in the way

  #4  
Old 10-07-2021, 08:28 AM
Jay S's Avatar
Jay S Jay S is offline
Chief Ponti-yacker
 
Join Date: May 2018
Location: Nebraska City, Nebraska
Posts: 858
Default

The difference in the flash and cruising couple depends a lot on the pedigree of the converter. The Hughes converters are pretty loose, they slip quite a bit very far (400+) under the stall. But a 2000 should work with what ever gear you want, it is basically stock. I would tend to agree with the 400-500 under for cruising though on a Hughes. A better more efficient converter can run 2000 under. I have a 4200 in one car that is coupled up by 2000, but open throttle it flashes to 4200, more efficient design than a Hughes, also much more $$$$. I have a 5400 race convert for Pro tree racing (very loose!). even it would hook good enough to pull the car 400under the flash. 100 rpm under sounds like something for a commuter bus…


Last edited by Jay S; 10-07-2021 at 08:35 AM.
  #5  
Old 10-07-2021, 08:46 AM
67Fbird's Avatar
67Fbird 67Fbird is offline
Senior Chief
 
Join Date: Mar 2021
Location: GA
Posts: 262
Default

as stated there is a big difference in convertor efficiency per maker. Best suggestion would be contact HUGHES. Not a BIG deal with only a 2000 converter and as usual instal with ANY automatic...add an PLATE type trans cooler!!

  #6  
Old 10-07-2021, 09:25 AM
Half-Inch Stud's Avatar
Half-Inch Stud Half-Inch Stud is online now
Ultimate Warrior
 
Join Date: Jul 2000
Location: BlueBell, PA or AL U.S.A.
Posts: 17,416
Default

13" has the least slip and mush. Stock 60-70s Big Car thru GTO, tight as you know.
For some reason the 4L80 stocker for gasoline engines has a nice stall but plays tight on cruise, where is not worth locking it up.

12" Hughes "2500?" ought to play well. Great balance on low-slip, low mush with highway gears, nice flash on a 455.

11"-10" better seek ATI or other spendy, proven converter.

  #7  
Old 10-07-2021, 10:56 AM
NeighborsComplaint's Avatar
NeighborsComplaint NeighborsComplaint is offline
Ultimate Warrior
 
Join Date: Aug 2009
Location: Elgin
Posts: 2,016
Default

You're fine, You're in stock convertor territory at a stall speed of 2,000. It's not going to slip or overheat.

__________________
Triple Black 1971 GTO. 455 + .040", Block zero decked and align honed. SD Forged rods, forged SpeedPro pistons, crankshaft oil holes chamfered, polished and balanced. 6x-8 heads with 1.77" exhaust valves, bowls blended, port matched and smoothed. Crane 284281 (234/242 @ .050 duration w. .488/.505 lift), Crane Hi-Intensity lifters, Crane 99838 springs & retainers. ProComp RPM clone w. 750 Quick Fuel Slayer, FlowTech headers, TH400 w. Hughes GM25 convertor, 3.55 BOP 10 bolt.
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 05:56 PM.

 

About Us

The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.

 

Cold Case Radiators

Cold Case Radiators is a Max Performance company that produces high end aluminum performance radiators at a price point that won't break the bank. Polished and stamped tanks. 2 rows of 1" tubes. Lifetime Warranty.

GTOG8TA.com

GTOG8TA.com is a Max Performance company that manufacturers parts for the 04-06 GTO, 08-09 G8, and 93-02 Firebird/Trans Am platforms.

Copyright © 2017