Couple of questions about gas mileage...

Jamie Miles

Well-known member
I am building a '69 1/2 Maverick. I am planning to put a 250 in it out of a 1974 Maverick. Here are my current plans:

Ignition: I am planning to use a Duraspark II distributor with the larger cap. I am going to put an MSD ignition box on it, with a "to be decided" brand TFI style coil.

Cooling: I am planning to use a 3 core Mustang radiator. I will be looseing the fan attached to the front of the water pump in favor of an electric fan. Question 1: Is it worth getting rid of the stock fan in favor of an electric fan? I have read time and time again how much of a drag the stock fans are.

Fuel system: I plan on keeping this all stock with a Carter RBS 1V carb, and I will get rid of the EGR on the 1974 engine. I am going for gas mileage here, not all out power.

Exuast: This is where my second question comes in. I really want to put a single out header on it, such as the one from Mustangs Unlimited since they are local to me. My exaust will Y off about mid way back under the car with "to be decided" mufflers or glass packs. I am mainly doing this because my current '72 daily driver is the same way and I love the look of it comeing out the back of the car and it sounds pretty decent. If I put a header on it, will it hurt my gas mileage any over running a stock manifold?

The transmission will be a T5. I will be using the T5 bell housing with cable clutch and '0 balance' SBF flywheel. I am planning to run somewhere around a 3.00 gear, however that will be decided after the car is running and I can figgure out for myself what gear feels and performs best to me.

This car will mainly be a highway driver, about 80 miles a day on the interstate. My current daily driver '72 Maverick is getting 25 mpg with a stock 250 and C4 that has a mild shift kit. It has a 2.79 rear gear. I would like to improve at least a couple of MPG over that.

The stock 250 has served me well for highway driveing so far, so I am not really to concerned about getting more performance out of it, just want to improve the driveability and gas mileage as much as possible. Does it sound like I am on the right track?
 
I think you are on the right track. As far as the fan goes, since you say your car will be used mostly for highway miles, you will be reaping the benefits of the electric fan most of the time since highway driving is when a stock mechanical fan is not needed and therefore wasting the most power (your electric will be shut off on the highway).

The header will not hurt your mileage, and it may increase it slightly. The T-5 will help a lot also, both because it has that OD gear and because it does not slip like an auto does, giving you a little more MPG on the highway.
 
Header won't really effect mileage.

Fan...I would make the electric fan one of the last upgrades. Sure, it will reduce some HP demands on your engine, but if you are keeping the 1V carb on there, for now...I'd just worry about the other stuff.

T5 is great for mileage...I went up about 4-5 MPG compared to the 2.77 3 speed.

Slade
 
Thanks. I bought the car with no drivetrain, so I will be installing the drivetrain and everything else all at the same time. The fan will be wired to a thermostatic switch through a relay. I will also have an over-ride switch to manually turn the fan on and off "just in case". I plan to use a dual electric fan setup from a old Honda Accord, so that if one fan were to go out I would still have a backup. It will be mostly highway driven, but I do sit in stop and go traffic in downtown Atlanta for about an hour 5 days a week.

Should be fun, I can't wait to get started on it. 8)
 
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