Torque convertors

Dec 6, 2017 12:55 PM - 190 Views Create A New Thread

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barryh

,



what is the minimum stall speed for a Chevy performance 350/290HP create engine?
I recently installed a new 350/290 Chevy performance create engine and reused my stock 1975 TH350 transmission (maybe around 1300 rpm stall). The engine seems to idle a little rough and tends to stall until the engine is warmed up.The installation instructions indicated a 'torque convertor with a higher stall speed on automatic transmissions' may be required. Chevrolet performance suggested a 2500 rpm stall however that's way more than I want for just a Sunday cruiser.
Has anyone been able to use a torque convertor with a 1500-1700 or 1700 - 2000 stall and if so what were the results?




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Comments
  • 36sedan
    Dec 11, 2017 at 7:40 AM


  • Changing the stall speed usually does not effect idle on a stock motor. However, as stated below, too low of idle rpm will cause trouble.
    Stall speed can effect how it holds back at a stop light, meaning brake pressure (foot) applied to keep car from creeping. On a high performance motor, too low of a stall can drop the idle speed and cause severe creeping.
    IMHO, a taller (higher) stall will make a hot rod much more fun to drive, anyone that tells you otherwise just doesn't know how it works. On mine it made a world of difference, even increased my MPG! I wished I had done it sooner. But be sure to get a good convertor, bargain basement ones are a waste of money.

  • barryh
    Dec 10, 2017 at 12:41 PM


  • I will try increasing the idle speed as it's free. I have been advised that I would not be happy with a 2500 stall so I'm tending to stay away from that.
    Besides can anyone tell me if changing the convertor to a higher stall speed will make it idle better?

  • 36sedan
    Dec 10, 2017 at 9:54 AM


  • Why are you afraid of a higher stall? In most cases a higher stall makes the car much more fun to drive and can sometimes evan add mpg. I installed a 2500 convertor in mine an increased my fuel economy almost 2 miles per gallon by letting the motor work in its power curve and in turn made for a lot more fun, lol!

  • crdnblu
    Dec 10, 2017 at 9:52 AM


  • Yes, it could be your convertor, but "idle set for 800 RPM in neutral" seems a bit low; this would normally be your in-gear idle speed to shoot for. Also, again, check the idle vacuum; if lower than 10-12 inches, it could indicate a vacuum leak.
    I'd suggest raising the idle speed to 900-1000 rpm in neutral, then give it a test start; it's free, & easy, and might cure your problem.

    Anyone else is free to chime in here, if I'm on the wrong track.......

  • barryh
    Dec 10, 2017 at 8:53 AM


  • The carb was tweaked and the idle set for 800 RPM in neutral but the engine wants to stall when first started. Chevrolet Performance advised a torque convertor with a higher stall speed was required and suggested consulting with a manufacture for their recommendation.

  • crdnblu
    Dec 9, 2017 at 10:21 AM


  • A few more questions:

    -What's your vacuum reading @ idle? Have you adjusted your idle mixture screws for the highest vacuum reading?

    -Have you tried adjusting your choke for a more rich mixture, or if too rich, tried a leaner notch? Additionally, is your fast idle cam operating properly, or is adjustment need to increase your cold engine idle speed?

  • will547
    Dec 9, 2017 at 9:45 AM


  • I have been told by a few transmission guys that the stall of a stock GM converter on the old stock Chevy is around 1800...


  • barryh
    Dec 8, 2017 at 11:04 AM


  • Initial timing is 10* BTDC @ 750 RPM with the vacuum advance disconnected as per Chevy performance instructions. The intake manifold is a Edelbrock Performer 2101 and the carb is a 1977 Rochester Q-jet with a electric choke.


  • crdnblu
    Dec 8, 2017 at 8:16 AM


  • I can't help you with your convertor question, but some added info from you may help with your engine issues. Can you tell us your initial timing setting, your vacuum reading @ idle, (without distributor canister connected, {if equipped}), manifold/spacer, and carburetor type, with mixture screws, & choke settings?



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