Topic: 66 C-Code Fuel Economy

[bryancobb]

These guys on VMF are trying to tell me I should be getting better than 20MPG on my concours, stock, 66 C-Code Convertible, with C-4 Automatic.
I can't remember the gears I have in the rear, but it was the normal bone-stock ratio...I think? 2.73 ??
Are they blowing me smoke?  I was under the impression that 11-13 would be more accurate.
http://forums.vintage-mustang.com/vintage-mustang-forum/636830-calling-all-engine-experts.html

[drummingrocks]

Bryan,

The stock gearset is most likely a 2.80.  I had the same setup as you (interestingly enough, my car was also Nightmist Blue), and I regularly knocked down 22-23 mpg with a stock 289, C4, and 2.80s.  The car didn't have A/C.

[ruppstang]

My 68 fastback with 289 auto and 2.79 gears gets 15-17 mpg. In 1974 I had a 1967 GTA coupe with 289 auto 3.00 gears that got 20+. That was leaded gas. Today if I use Ethanol I can count on a mile or two less mpg. Five years ago we had a 67 coupe 200 6cil with auto and 2.82 gears it would get 22-23 mpg.

[bryancobb]

I STAND CORRECTED THEN.  If you guys want to read the thread there, and see if you can help me find why I am running slobbery rich,
by all means contribute.  I'm at the point that I am thinking somebody may have enlarged my jets in the past or something.
http://forums.vintage-mustang.com/vintage-mustang-forum/636830-calling-all-engine-experts.html

[MattDoscher]

I'm getting 18MPG in my '65 w/ 289 C-4 & Autolite 4100.

[jwc66k]

I drove from Massachusetts to California in a 66 Mustang "A" code Fastback, 4 speed, 3.00:1 rear axle. Here are the numbers: distance - 3,177 miles; fuel used - 176 gallons; driving time - 48 hours; ave speed - 66.1 mph; mileage - 18.1 mpg. I got at least 10 hours sleep each of three nights stop (Joliet, Ill; Cheyenne, Wy; Ely, Nv). I learned to keep traveling records, mileage, costs, etc, from my father, a WWII USN pilot.
My 66 "A" code hardtop, C4, gets 13.1 mpg in mostly city driving with the lousy California gas. This is over 20 years of records. My 66 "K" Fastback has a 10.4 mpg average but is only driven about 250 miles a year (mostly up the street to "stretch its legs"). Anyone who claims over 20 mpg in a Mustang V8 needs to get their mileage using at least 1,000 miles worth of consecutive records.
Jim

[bryancobb]

Here's my tag.  I am not absolutely sure the gears inside are what's shown on the tag.  My carrier came out of a 67 and it's the wrong one.  I intend to get the right 66 unit in the future.
Can some of the experts tell by the pics what gear set I have.  I wish I had counted teeth when I had it out.

[Brian Conway]

Your Tag indicates a 2.80 gear ratio.  The top W# is the axle model, to the right of the gear ratio is the Date ( year-month-week) The last number grouping is the plant coding.  The best every, freeway, in my stock, 65, GT, 4 spd is 19 MPG.  Two previously owned stock 66, C code autos, right at 15 MPG.  Just about the same for a stock 66, 6 cyl. auto I owned for 30 years.  I think todays terrible gas, California, and the awful stop and go traffic really takes a toll on getting any kind of decent milage.   With the 428 CJ: never checked.  Brian

[bryancobb]

My car is a MAR 66 Metuchen car.  I'm pretty sure the TAG and axle housing and axles are original to my car.

The differential has obviously been changed.  I'm not sure what I have.  Maybe a REAL SHARP expert
could see enough detail to tell me what ratio I have.

[C5ZZKGT]

I STAND CORRECTED THEN.  If you guys want to read the thread there, and see if you can help me find why I am running slobbery rich,
by all means contribute.  I'm at the point that I am thinking somebody may have enlarged my jets in the past or something.
http://forums.vintage-mustang.com/vintage-mustang-forum/636830-calling-all-engine-experts.html

Bryan, DID Kurt run test your carb?? he should have noticed any enlarged jets during the rebuild/restoration and run test.

[jwc66k]

How about some basics. What is the number on your carburetor? Did you open it and verify the jet's size? They should be stamped "50F" and have a hole diameter of 0.049inch. Over time they get "smaller" with a build-up of gas additives and other crap that in there. Many mileage problems can be traced to a blown (or leaky) power valve too.
Jim

[J_Speegle]

Recall, in my parents factory 65 convertible they had in the late 70's, getting low 20's (think it was 21 or 23 on a long trip one time - fairly flat trip to so Cal.

A code 4 speed unrestored car that Ford purchased from them as a contest car in the 80's

[bryancobb]

Bryan, DID Kurt run test your carb?? he should have noticed any enlarged jets during the rebuild/restoration and run test.

You may know more than I, but I don't think Kurt has the capability to run a carb on an engine.

[bryancobb]

How about some basics. What is the number on your carburetor? Did you open it and verify the jet's size? They should be stamped "50F" and have a hole diameter of 0.049inch. Over time they get "smaller" with a build-up of gas additives and other crap that in there. Many mileage problems can be traced to a blown (or leaky) power valve too.
Jim

Jim click on the link above and go read the thread on VMF.  There's pictures of it.

[jwc66k]

At this stage, replace the carburetor with an off the shelf rebuilt one and see what you get.
Jim