But the powerglides are great for passing. My Mom had a 1969 Impala with a 300 hp 350 engine. Stand on it at about 50 mph and it would shift into first and really set you back in the seat till about 75 mph when it shifted into second. That was about the only thing that car was good at....The Powerglide was a 2 speed automatic. Even though this car had an engine of 400+ cubic inches, it took a long time to build up any speed whatsoever...