Topic: 66 C-Code Fuel Economy

[ruppstang]

You can get close to knowing the rear Axel ratio by jacking up the rear Axel and counting the tire revolutions to one turn of the drive shaft.

[51f1truck]

Rotating the one tire and then counting the rotation of the pinion will work but there are a couple of things to check.  They deal with whether you have an open differential or a Limited Slip Differential.  Here is a link to a website that can help:

http://www.jedi.com/obiwan/jeep/misc/gearratio.html

and I will copy some of his words of wisdom here:

So, assuming you've got an axle up in the air with the driveshaft disconnected & neither wheel on the ground:

If you turn one tire & the other one either stays still while the pinion rotates, or the other one rotates backward while the pinion stays still, or something in between, then you've got an open diff or a very weak LSD (like a Trac-Lok with too many miles on it). In this case, you need to secure one wheel (perhaps by lowering the tire onto the ground), then you can figure your gear ratio by rotating the airborne tire TWO full rotations and counting the number of times the pinion rotates. 3.73 turns means 3.73 gears. If you only rotate the tire once, then 1.865 turns means 3.73 gears.

If you turn one tire & the other one turns the same number of turns in the same direction, then you've got a good LSD or locker. In this case, you can just rotate the tires ONE full rotation and figure your gear ratio by counting the number of times your pinion rotates. 3.73 turns means 3.73 gears.

Good Luck Bryan!

Fred

[bryancobb]

Thanks,
I just haven't checked.  I'll do it this weekend.
I don't remember doing it but knowing my way of thinking...  I would have confirmed that the unoriginal differential had the same ratio as the tag, while I had it out, or I wouldn't have put it in.

[gjz30075]

Bryan, it might be best to get over to Mo's Speed Shop in Dallas  http://www.mosspeedshop.com/     They have a chassis/rolling road dyno with an excellent diagnostician running it;  name's Jeff.     He's very good with carbs.     I think it's worth the money (maybe $100 or so for an hour) to get you pointed in the right direction.

[bryancobb]

Bryan, it might be best to get over to Mo's Speed Shop in Dallas  http://www.mosspeedshop.com/     They have a chassis/rolling road dyno with an excellent diagnostician running it;  name's Jeff.     He's very good with carbs.     I think it's worth the money (maybe $100 or so for an hour) to get you pointed in the right direction.

++1   I'll definitely do that!
Didn't know about them.

['65 Full Throttle]

Please keep everyone posted on what you find out!

[bryancobb]

Will Do!  I'm all wrapped up into restoring the convertible top frame right now!

[Jays66gt]

My 66 Mustang "A" code coupe, 4 speed, 3.00:1 rear axle consistently gets 18 mpg on 93 octane.  I've achieved just over 19 on a couple of occasions.  Don't know what I did differently to get 19, but I did get it.  20-22 with an automatic seems like a stretch.

[Pete Bush]

With gas at $4/gallon, many of us have renewed interest in fuel economy.

Although not related particularly to it's 289 big brother, there's a nice little article regarding the 200 six cylinder in Shop Tips Vol. 6 No. 10 June 1968. Author Ak Miller takes a stock 1967 6 cylinder 3-speed which he measures at 65 horsepower, and through a series of performance upgrades increases the horsepower to 100. And then runs a miles per gallon trial with an averaged 36 mpg!

Now admittedly some of his modifications aren't exactly Concours (headers and swapping carburetors), but some wouldn't be visible to a judge - Carburetor re-jetting, ignition timing, and camshaft upgrades.

Interesting reading and a good source of improvements for the six cylinder crowd - and by analogy their eight cylinder big brothers.