Recently purchased a good looking 1968 280 S. Have found to be getting around 10 miles to the gallon, is this normal ??
After say fitting a new air cleaner ( Canister type ) are there any other things anyone can suggest to may be obtain a better economy.
Ray Melbourne Australia
PS Lovely car for its age
-- Ray Cuddon
3 / 4 Girdwood Road Boronia 3155 613 9762 5999Call up MB Australia... and talk to their classic department... ask about the fuel mileage... I think should be alot higher than 10MPG.
Ray,
If your 280S has dual Zenith INAT 35/40 carburetors, I can offer a few suggestions.
First, they should be properly synchronized and adjusted.
Second, the Zenith 35/40 carburetors have an electric choke mechanism where the car's choke plate defaults to about one-quarter closed with the engine off. When the car is started, electric heating elements warm bimetallic springs to fully open the choke plates. If the electric heating elements are not working or are misadjusted, the car continues to run at one-quarter choked, using more fuel than it should.
It's also possible that the choke plate was overadjusted to compensate for worn carburetors (leaking air from worn throttle plate hinge openings), a cracked base (vacuum leak), or aging engine compression.
My 1968 280S was a great car, a real beast on the road once I got the carburetors figured out. It took awhile to understand the Zenith carburetors, but it turned out to be far more simple to adjust, synchronize and tune than I had originally thought.
Weber makes a conversion kit for the Zenith INAT 35/50 dual carburetors, but I really liked the original setup once I got it adjusted. I remember mileage being in the 12-18 mpg range.
With two four-barrel carburetors on an inline six-cylinder engine, you're running almost one carburetor barrel per engine cylinder at low speeds, and over a barrel per cylinder at 60 mph and above. Great for performance, but expensive for heavy-footed driving.
If you want to check some carburetor settings, send a note to rugbygynw at yahoo dot com.
Regards.
Low mileage from a gas engine could be due to:
Too low an operating temperature - below 80 degrees C. replace thermostat. Too rich an air / fuel mixture - carburetor problem. Worn out spark plugs & ignition wires. Retarded ignition timing, check ignition timing and adjust.
All that said, the mid '70s 116 280S version sold in the USA was certainly no economy champ, 13 to 16 MPG (US) overall as I recall.
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