Hello. I'm driving a 1970 Dart with the 225 /6 in it and a 3 speed automatic. My question is this: What kind of speed would it be wise for me to top off at? I like to drive at like 75-80 on the freeway in my other car, but that's a 93 nissan so I don't really care about how hard it's working... I don't want to hurt my Dart though. Thoughts?

Thanks!

When your Dart was built, there were several large Western states that had no limit, or at least no daytime speed limit, on the Interstates. You could legally drive for hours on end at 80, 85, 90, 110...and that was with '60s-'70s tires, brakes, lights, attitudes towards drunken driving, etc.

Most '70s like yours have tall highway-flyer gears in the rear axle (2.76:1). As long as the car's in proper repair, there are good safe tires on it, and your brakes and you are up to it, there's no reason to artificially limit the speed at which you drive just because the car is old.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I agree. I often drive at 70 - 75 with my 68 Dart 225 with 2.76 gears. But the limiting factor is the brakes. Here in Massachusetts the roads are crowded with crazy drivers. Until I replace my 9" drums up front with discs, I'll tend to keep closer to the speed limit. And I always try to keep several carlengths between me and the car in front of me at highway speeds.

-Mac

Like Dan alluded to, the condition of the engine and any mods make a difference, too. Before installing my Super Six and Dutra Duals, my Swinger struggled at 75 mph, and it just didn't feel right (engine-wise) at higher speeds (and I have highway gears). Now at 75, it just wants to go faster!

VM

I cruise in my Duster for hours on end at 75-80 MPH when going to car shows, running the air conditioner and the radio blaring. The only problem I've had is the carburetor one time iced up after running 80-85 MPH for 3 hours. If I keep the oil right above the add mark it won't lose a drop. Now why is that? Fill it up to the proper level and it will lose the oil in 2 days time? Weird

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

i took my dart up to 75 one time i didnt have a tach but man was she screaming, it had very high gearing (charlie told me probably 3.55's) when i finaly got a tach the thing would redline(light would come on at) 3800 which is where i set the light. at about 60-65 i didnt have a working speedometer then

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Cuda Progress
The dart as it sits now

In OD I regularly cruise at 85mph.....can do 105 in 4th......can cruise at 105 in 5th but it is tiring......and hard on tires......and really noisy.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Your car was designed for 70+ MPH, so as long as you have good tires, brakes, suspension and drive train, you're car will be fine. Drive mine every day 65-75. Always drive for conditions though, and no tail-gating!