MPG - What Do You Get?

[CommanderToasty]

So what kind of fuel performance are you getting in your 289? City Vs Highway. What is your configuration from stock to various modifications and how did they change your MPG?

[PackardV8]

With an R1 automatic and 3.73 gears, I got about 12-14 in town and 14-16 on the highway. With the 700R4 overdrive, it now gets 18 MPG on the highway. With that improvement, it will only take about 100 years to pay for the trans swap. The reduction in noise made it worth the money spent the first year.

jack vines

[okc63avanti]

My R1 engine was bored 0.060" over (299 cu in), has hypereutectic pistons, R3 SS valves with ported heads, ported and polished aluminum R3 intake, polished R3 exhaust header, 276 deg cam and will be fitted with an edelbrock AFB, Paxton Supercharge with High output impeller, and a Mopar HEI ignition. Basically an R2+ configuration. My rear end was rebuilt with 3.73 ratio and Auburn gear posi-trac. The transmission is a Tremec TKO 600 with a final OD gear ratio of 0.63.

I'm curious as to what others running a 5 speed trans on a R2~R3 clone engine might be getting for mileage estimates.

[PackardV8]

Supercharged cars with primitive 1960s carburetor and ignition technology required over-rich jetting at cruise in order to prevent detonation under boost. There is also the continuous parasitic drag from the supercharger and the belts. Thus, most R2 and R3s with 3.73 rear gears are 10-14 MPG cars. Your 3.73 x .63 gives a 2.35 final drive ratio. That will help considerably, but it's still improving on a low starting point.

If you spend some time and money on the chassis dyno and have someone who really knows how to jet the Edelbrock AFB and curve the distributor, 16-18 MPG should be possible on a steady highway cruise.

FWIW, do an odometer check over several 10-mile test sections. With tire changes, transmission swaps and age, most Stude odometers are off enough to matter in MPG calculations.

jack vines

Edited October 15, 2011 by PackardV8