1974 Plymouth Valiant 225 slant six from North America
Reliable but thirsty
New radiator cap.
Tightened up loose radiator hose.
I bought this car from the original owner. It had been sitting in a garage since 1996. I bought the car late December of 2011. Amazingly the car started right up after replacing the dead battery. I filled up the gas tank, aired up the tires, topped off all the fluids, and drove it 45 miles home. A tune up and some general tinkering brought the car up to snuff. Mechanical parts are very cheap and readily available, which is a huge plus.
It rides and handles about as well as I'd expect for a 70s car sitting on ancient bias ply tires. The manual steering takes very little effort, even at a dead stop. The car accelerates adequately, although it won't win any races. Brakes are good for all drum manual units, although there is some pull.
It has been reliable, although for a small six cylinder, the fuel mileage has not been very good. I expected 20-22 mpg, but the car averages 15-17 mpg in country driving. Also it pings badly on anything but premium fuel, which makes driving the car any sort of distance costly. I've retarded the timing, which has helped. Also mildly annoying is the lack of hydraulic lifters. I'm baffled why Mopar went with mechanical lifters, when all the other major manufacturers had hydraulic lifters. As such, it's a loud engine; perhaps a valve adjustment will quiet it down.
The interior is plain, which I like. The bench seats are comfortable. Generally the quality seems to be pretty good. Underneath the hood, the Valiant is very easy to work on.
Generally I like the car, but the fuel mileage means that it'll be up for sale before too long. I have to go long distances to work that doesn't pay very much. It really hurts the wallet when my car guzzles up a third to half a day's wages.
Would you buy another car from this manufacturer? Yes
Review Date: 6th February, 2012
Be sure to replace those ancient bias ply tires, so you can be safe on the road.
You are right, a Slant 6 should get better than 15-17 mpg. I agree that you should be expecting 20-22 mpg, maybe even higher on the highway.
If you've really done nothing to it but change the battery, a tune-up could be in order -- plugs, wires, cap and rotor, air filter, oil change, fuel filter. And yes, check that timing. Knocking the timing back may have solved the pinging, but could also be negatively affecting gas mileage. Make sure the timing is correct to start with.
I had a '64 Dodge with a Slant 6, and my family had several Plymouth Volarès with the Slant 6, and they all ran on the "regular" lower octane fuel without pinging. You might have some carbon buildup in the head, which has increased the compression ratio.
Also, an old, carbureted car like this is a lot more sensitive to driving habits, so if you put your foot on it, gas mileage will suffer more proportionately than modern cars that have a computer to compensate for it.
Anyway, it is fun to still hear stories like this about finding a '74 Valiant in a barn, and starting it up to drive home.
My name is John. My Valiant gets 28 MPG city, but stock it's got 20-22. You can contact me at email@example.com. Put 1972 Plymouth in the subject.