450 SLC mileage?

Question

Hi Gang,Just figured out the mileage I'm getting on my "new" 1973450 SLC. Its getting 9.8 MPG, which seems really bad.This has been for mostly in town driving.Does anyone out there know what they should get?                 Steve

Ennui Society · Accepted Answer

Hello,The mid-Seventies was really bad for the vehicles and pollution control systems. The new regulations went into the effect that really killed lot of power and increased lot of fuel consumption until the manufacturers figured out ways to rectify both.Some examples: 1975 Chevrolet Nova with six-cylinder and three-speed gearbox got 9mpg in city driving! 1975 Cadillac Eldorado with 8,2-litre V8 motor went from 425 horsepowers (in 1970 edition) to 180 horsepowers.That doesn't necessarily mean your 450SLC is gas hog. It is more likely that it needs tuning up and pollution control system checked carefully.My former 1982 Buick Skylark with 2,8-litre V6 motor and automatic gearbox went from 18mpg average to about 5 to 6mpg after "shady-tree" repairs from engine fire. I couldn't figure out the pollution control system so I sold it right after I got it back to running.Regards,OliverSteve wrote:

Steve · Answer

Hi Gang,Just figured out the mileage I'm getting on my "new" 1973450 SLC. Its getting 9.8 MPG, which seems really bad.This has been for mostly in town driving.Does anyone out there know what they should get?                 Steve

Bill Ditmire · Answer

It may not be economically worth the trouble to optimize the mileage, but here's what to look at: Adjust the valves, check the timing and timing advance; the CO at idle fully warm should be about 0.7% (under 1.5% for sure) and the timing retard should cancel itself A. if the engine is not warmed up and B. if the coolant temp exceeds 212 degrees F. (ground the wire to the brass switch above the thermostat housing and the idle should increase).

With all that in order, you should be able to get 12 in city driving and 20 on the highway.

Bill Ditmire Ditmire Motorworks,Inc.

425 White Horse Pike Absecon,NJ 08201

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609-641-3392

Bill Ditmire · Answer

The pollution control system of the 1973 450SLC consists of: a distributor vacuum retard. That's it. No air pump. No catalyst. No lean-burn system. The cars had 225 HP and, at 3,670 lbs dry, were no lightweights.

Bill Ditmire Ditmire Motorworks,Inc.

425 White Horse Pike Absecon,NJ 08201

formatting link

609-641-3392

450 SLC mileage?

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