Folks just don't understand how converters really work. It's a fluid coupling, so without a clutch inside of it, they all have some slippage, even stock ones. When folks see someone mentioning 3200rpms stall speed (for example), they think it takes at or near that rpm to move the vehicle. Some have also had associations with cheap "shelf" converters that are extremely "loose" everyplace, and never do couple worth a crap at any rpm.
A good street converter will act and drive just like a stock unit, yet allow the engine to see some additional rpm's with good traction when hit with full power, over a stock type converter.
Even my 10" unit would work fine in a heavy car with a low (numerical) axle ratio. It move the car right off idle, and doesn't flash up at light load in any gear.
Load stalling it holding the brakes it will overcome the tires at 1900rpm's.
Any heavy throttle in high gear at low vehicle speeds, like climbing a steep grade, the engine will see about 2200-2400rpm's.
At the track with perfect traction, it flashes to apprx 3500rpm's, enough to put my daily driven car DEEP into the 11's in full street trim.
The 13" Continental unit nearly as good as the 10" unit. My old 455 would send one to just over 3000rpm's at the track, it was every bit as tight at every level as the stock converter it replaced otherwise. I couldn't get the engine much past 1700rpm's on the brakes, and about 2000-2200 loading it pretty heavy on the street for passing situations, climbing steep grades, etc. It ran nearly as quick in 60' times as the 10" unit that replaced it!
I mentioned it in association with this thread based on the goal(s) of the vehicle. The converter would be the best place to spend money, especially with this application, where the owner wants to keep most things pretty stock/mild, and still the ability to unleash the big 455 torque when it's needed.
We just helped two customers with very similiar set-ups, one replaced an early 4 speed auto with one of our TH400's. We installed a low 1st gear set, and 13" Continental converter, backed by his 2.56 axle ratio. He now has big car that drives great, gets good fuel economy, and launches hard with a little traction!........Cliff
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https://cliffshighperformance.com/
73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile),
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