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For anyone who hasn't been following along, short story is in I'm in the process of rebuilding my original 400G block out of my '69 442. In discussions with @cutlassefi it was determined I need to look for a converter that has a stall of 2600-2800.
I have multiple emails out to the top of my head converter companies (TCI, Hughes, Hays, B&M)..and so far TCI is the only one to respond thus far with either a Breakaway at 2400-2600 stall, or another one (haven't looked up the Part#) that stalls at 2600-2700..but was warned it was almost triple the cost.
I guess, first question would be what size do I need (9", 10", 12") and second, does anyone have any suggestions knowing what stall range I've been advised to look at?
..just heard back from Hughes, they're suggesting the GM20-HD at 2,000 stall. They followed up with this: "The reason for the slightly lower stall is that the new converters are built on a smaller diameter core (10.5" versus 12") so they react different to big blocks with good TQ."
I mean, it makes sense..but I also know little about all of this.
10" is overkill IMO. 12" is fine TCI, Hughes, Coan, B&M all good. Strangely I no longer see 12" converters listed?
The chart is snipped out of Jegs under the TCI brand. Note big & small block columns.
10" is overkill IMO. 12" is fine TCI, Hughes, Coan, B&M all good. Strangely I no longer see 12" converters listed?
The chart is snipped out of Jegs under the TCI brand. Note big & small block columns.
I'm not sure where I read it, but the 12" cores are very hard to come by so they just went to 10".
That being said, a 10" breakaway would be ample, based on the idea that the smaller size can actually run more efficiently at the lower stall...correct?
I'm not sure where I read it, but the 12" cores are very hard to come by so they just went to 10".
I remember reading that as well. I think it was in a torque converter thread where it was also said the BPO threaded lug style converters weren't available any more, and the converter companies were using the cores with ears that use the bolt/nut setup instead.
I built a 400 trans for a motor home about 6 months ago, TransStar won’t even sell a stock converter without a core. The stock 12-13 inch converter cores are getting scarce. Who would have thought that would happen? I’m sure everyone scrapping stock converters for years played no small part.
I recall reading somewhere the industry standard for rating converter stall speed is 300 lbs/ft of torque at a specific rpm (I dont remember what that speed is). If the engine makes more torque at that speed, the stall speed is higher, lower torque, lower stall speed. Vehicle weight and gear ratio plays a big part in stall speed also.
Converter science has come along way in the last 20 years. A good high stall converter won’t feel mushy at part throttle.
I’d call Hughes, Coan, ATI, whoever you prefer and get a converter recommendation.
I built a 400 trans for a motor home about 6 months ago, TransStar won’t even sell a stock converter without a core. The stock 12-13 inch converter cores are getting scarce. Who would have thought that would happen? I’m sure everyone scrapping stock converters for years played no small part.
I recall reading somewhere the industry standard for rating converter stall speed is 300 lbs/ft of torque at a specific rpm (I dont remember what that speed is). If the engine makes more torque at that speed, the stall speed is higher, lower torque, lower stall speed. Vehicle weight and gear ratio plays a big part in stall speed also.
Converter science has come along way in the last 20 years. A good high stall converter won’t feel mushy at part throttle.
I’d call Hughes, Coan, ATI, whoever you prefer and get a converter recommendation.
Hughes has me at a 2,000 stall, which doesn't seem to line up with what the cam calls for. I've also sent a message to Coan (never had heard of them) so we'll see what they say.
Hughes has me at a 2,000 stall, which doesn't seem to line up with what the cam calls for.
Your post above said Hughes stated the "2000 RPM" converter will actually stall higher than that behind a big block. I would believe them as they do this for a living and have a very good good reputation.
Originally Posted by brotherGood
..just heard back from Hughes, they're suggesting the GM20-HD at 2,000 stall. They followed up with this: "The reason for the slightly lower stall is that the new converters are built on a smaller diameter core (10.5" versus 12") so they react different to big blocks with good TQ."
Your post above said Hughes stated the "2000 RPM" converter will actually stall higher than that behind a big block. I would believe them as they do this for a living and have a very good good reputation.
That's fair, I was just looking at the cam info as well, so that's what geared my train of thought.
Hughes has me at a 2,000 stall, which doesn't seem to line up with what the cam calls for. I've also sent a message to Coan (never had heard of them) so we'll see what they say.
I worked at Coan 25 plus years ago, their stuff is top notch, as is ATI and Hughes. Dave Coan and Steve Grinder invented the internal hydraulic style transbrake for the Powerglide in 1971. Coan and ATI pretty much created the performance automatic transmission industry. Before they started building custom converters, the hot setup was to use a 6 cylinder or air cooled converter in your race car. Sure, it gave you the stall speed you wanted, but a converter designed for 100 hp won’t last long with 600hp!
The 2000rpm converter will probably go to 2400 behind a torquey engine.
After a couple days' of dialogue via email with Todd @ Coan, I placed an order for their 2600-2800 Pro Street converter. Once they get back in stock, theyll ship it out. In the meantime, I've gotta go ahead and hook up a trans cooler (half expected to do so anyway)
March 9th, 2022, 05:39 AM
