Question about 1977 450 sel (4.5 liter)

[jpomerenke]

I just purchased a 1977 450 sel (4.5liter) with 75,000 miles on it. I have never drove a old 450 sel and i bought it because i got a great price on a low millage classic in great shape.

While driving it, it takes a little while to get up to the 30-40 mph range. This is normal i am assuming for such a heavy car with a 3 speed transmission in it.

The main question i have is ..... at around 40 mph the car gets really sluggish like it has no power at all and then the second it gets above 40 mph it has its power back and picks up speed really fast and drives like a dream.

Is this normal for it to become so sluggish at around 40 mph?

Thanks!

Joey