When my '70 Monaco 383 4bbl was my daily car, it started to get a driveline harmonic at 100mph, so never had it above that. With HD shocks (from back then, when they were what they should have been), 90mph was a comfortable speed. I felt confident at that speed on the Interstates when traffic was light or less. With others around, about 78 was the limit for a quicker slow-down from 70mph. Didn't know where to take it to get the driveshaft looked at, back then, so it stayed as it was.
I was in junior high school when we got our '66 Newport (with 7100 miles on it). We were taking our first decent trip in it to west Texas. We left home and were the other side of Odessa when it was about 10pm or so. I had noticed that our cruising speed had crept upward, with my father driving. Finally, he proclaimed that "This car just wants to run 90", so we did.
In later life, with HD shocks on the car (from back then) and the tires at 30-32psi, the car would sit at 70mph with no problems. Once you got to 75mph, it was like "let's have some fun". The upper end of that feeling was 90mph, which was about 3100rpm. Past that, the 383 2bbl took a bit more throttle to increase speed and the suspension was a bit soft, so 90mph was just fine. Everybody had fun. At 70mph, it was bored . . . at 75-90mph, it was "smile time".
Would those cars run faster? Certainly! But to get there, there had to be a good reason to push them to it. One thing I liked about that '70 Monaco 383 4bbl, once the throttle was cracked to about 3/4 open, it had NO problem or trouble getting to "triple digits" quickly and easily, unlike any other car I've had. 20-100 took about .4 mile to happen. It knew what it liked! One of my fantasies was for Springstein's "Born To Run" come on the FM Multiplex, have about 10 miles of open road ahead, and let that AVS inhale through the dual snorkels, everything exhaling through the HP manifolds and factory dual exhaust, everybody having fun.
Having the rubber bushings and such replaced is good, but no guarantee of "high speed handling". For that to happen as it can, you need some good HD shocks all around and good tires at 30-35psi inflation. And then the good sense to know when to slow down, as conditions present themselves!
Of course, now-a-days, any little 4cyl with a triple OD automatic can run 80mph with ease, but getting past that takes horsepower it might not have, even with a "glowing red turbo". So the dominance of a 383 or 440 on the Interstates is not what it used to be, but still credible (with 3.2 or 2.7 gearing). So just cruise at elevated speeds on the Interstates and enjoy the Chrysler product you might be in!
just some thoughts and experiences,
CBODY67
