Old 10-06-2021, 05:50 PM
Rar_421 Rar_421 is offline
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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

Old 10-06-2021, 06:55 PM
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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?

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Old 10-06-2021, 07:02 PM
Rar_421 Rar_421 is offline
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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

Old 10-07-2021, 08:28 AM
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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.
Old 10-07-2021, 08:46 AM
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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!!

Old 10-07-2021, 09:25 AM
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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.

Old 10-07-2021, 10:56 AM
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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.

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