2.80's--4.11's gas milage?

[Jeff65]

20 or above is considered good. 15-20 marginal and less than 15 poor.

Typical cars in factory configuration and in good condition and state of tune get 18 mpg city and 20 mpg on the highway.

Cars with numerically high rear axle ratios will get lower gas mileage due to higher engine rpms at highway speeds. It isn't directly proportional but approaches it. Hence if you have 3:50s instead of 3:00's the mileage expectation would be:

3:00/3:50 x 18 and 3:00/3:50 x 20 => 15.4 city and 17.1 highway mpg respectively.

Compare this to a 5 speed, then the numbers are something like:

3:00/3:50 x 18 and 3:00/3:50 x 20 x 1/0.68 = 15.4 and 25.2

The reason for this is the overdrive gear in the 5 speed provide a lot better highway mileage. In actuality, a carbed engine car will not get 25.2 mpg on the highway but will get 22.5. An EFI engine will get the 25.2 mpg.

I'm very new at this...

can you explain this ratio thing a bit...

3:00/3:50 x 18 and 3:00/3:50 x 20

i presume that most cars are standard.


what's an efi motor??

[Jeff65]

The factory gear ratio for an A-code Toploader 4-speed car was 3:00 (normal level of performance).

The factory gear ratio to a HiPo K-code Toploader 4 -speed car was 3:50 (high performance option).

I've used the above two as examples of what happens when you change gear ratios. I make the assumption that the city/highway mileage was 18 and 20 mpg respectively for the A-code car. I was a young guy in my early 20's when the '65 was a new car. My dad owned a early '65, then '66 then '68. I owned a new '67 and my brother owned a '69 so I remember what kind of gas mileage these cars used to get when new. The mpg quoted may not be perfectly accurate but its close.

Knowing that, I predict what happens to the gas mileage when the gear ratio changes from 3:00 to 3:50. It will be worse for 3:89 and 4:11 by about the same percentages. Just plug in 4:11 into the equations and you'll see the mileage drops down.

I also provided the gear ratio in fifth gear for the T5 transmission which is 0.68 rather than 1.00 which is fourth gear for the Toploader 4-speed and also top gear (3rd) for the Toploader 3-speed.

EFI = electronically fuel injected.

Oke thx

What V8 engines whould fit in a ford mustang '66 and what gearboxes are availble.

I'm asking this because i really wanna buy a '66er, and want to have a nice acceleration but a decent mileage.

the fuel is here 1.10 euro/ltr yes 4.18euro(same as dollar) a gallon...so the mileage must be decent....

what does the '66 need for fuel unleaded or premium(with lead?)?

are the standard engines ready for LPG use(valve seats)?

[Jeff65]

Originally posted by Edelbrock
Oke thx

What V8 engines whould fit in a ford mustang '66 and what gearboxes are availble.


I'm asking this because i really wanna buy a '66er, and want to have a nice acceleration but a decent mileage.

the fuel is here 1.10 euro/ltr yes 4.18euro(same as dollar) a gallon...so the mileage must be decent....

what does the '66 need for fuel unleaded or premium(with lead?)?

are the standard engines ready for LPG use(valve seats)?

1. The "Windsor" family engines bolt in. These are 221, 260, 289, 302 and 351w. The first four listed bolt in directly with the right parts. The 221, 260 and early 289 had a five-bolt skirt and matching bell housing. The late 289, 302 and 351w had a six-bolt skirt and matching bell housing. The late 289, 302 had 157 tooth flywheels and the 351w had a 164 tooth flywheel. The 157 tooth accommodates clutches up to 10.5". The 164 tooth accommodates clutches up to 11". Of these engines, only 260, 289, 302 and 351w were used in production Mustangs. The usual V8 '66 Mustang is a 289 2v, 4v or HiPo. This means 2 barrel carb, 4 barrel carb, and high-performance 4 barrel carb.

2. An A-code 289 V8 with 3:00 gears is no slouch performance wise but neither is it going to win races. Give it some hop up items such as better breathing heads, a mild cam and 3:50 gears and it starts getting exciting. My '65 with Ford Racing 302 and 3:50 gears and a T5 transmission hauls. It puts you far back in your seat when you want it to.

3. If you have the money to spend, the combination I've given you is best for your situation but it is expensive to do what I've done to my car. Here's the gist of it.

If you bought a '66 for restoration then upgraded the engine with a Ford crate 302 roller cam engine (5.0L) then added EFI, T5 transmission and 3:50 rear gears you'd have a high performance car and still get 25 mpg on the highways. Around town you won't get this best gas mileage since you'll not get the car to run smoothly in fifth gear until you reach 45 mph or better. If you like I can convert the mpg to kilometers per liter and kilometers per hour.

4. If you set up the car as I suggest, you can use 87 octane unleaded pump gas. You'll have to adjust the timing slightly from optimum to avoid pinging but the car runs okay. I know, mine is set so. I use 87 octane unleaded regular gas. Note, methods of calculating octane vary from country to country. I think 87 here is like 2 star in Great Britian.

Let me say you can do this with a factory 289 as well. You do need the five speed to get this kind of economy and still have punch from a standing start. Tell me what your budget is and I can better advise you of what to choose.