Gas mileage

[JohnG]

hi everyone

I bought a 58 hardtop in 2003. As it had 150,000 + miles on i, there was not much that didn't need work. None the less I drove it alot while fixing various parts.

Each summer I make a trip in early July from my place in MA up to a friend's in Maine, 240 miles, all highway, 65-70 mph. A good trip for comparisons.

In 2005, with a worn out engine, I got 13.3 mpg (also used a quart of oil every 125 miles...). Stock ignition and a Holley carb someone put on it long ago.

In 2006, with a rebuilt engine, same trip, I got 15.5 mpg (and used no oil at all. Alot to be said for new pistons and rings).

In 2007 I changed the coil to an MSD 8002 with matching MSD ballast resistor. Also increased the plug gap to .042". This time I got 17.3 mpg.

In the future, I plan to increase the plug gap further as one variable, and I also have a completely rebuilt Fomoco carb that was used on 352's. I am pretty confident that 18 or more is attainable.

On a different note, last summer I almost died of heat coming from the tranny. I got under the console and put a bunch of insulation used on water heaters and had a very comfortable ride this time.

Alexander, where's that cup holder?? I had to use a roll of duct tape!!! Wasn't even color coordinated!! ****!


John

[Guest]

Boy that some great gas milage I only get around 10 to 14. Maybe we have more hills here than where you live at? Do you have a six cylinder in your car? Well I guess I might as well pay through the nose for my fuel as it would my cost factor to do all that work you did would brake my little piggy bank and leave me with no mo-la for fuel. Jon

[Guest]

Boy that some great gas milage I only get around 10 to 14. Maybe we have more hills here than where you live at? Do you have a six cylinder in your car? Well I guess I might as well pay through the nose for my fuel as it would my cost factor to do all that work you did would brake my little piggy bank and leave me with no mo-la for fuel. Jon

[JohnG]

That was flat highway driving, near constant 65-70 mph. About as optimal as it gets. I don't have much confidence in the local, stop and start driving. Too much sheer mass !

Aside from the rebuilt engine, which was pretty much a "must", the addtional modifications were about $45. The coil was $30, the ballast $12, and gapping the plugs free. It won't take long for the coil to pay for itself with gas being $3/gallon. For the 480 mile round trip, comparing 15.5 vs 17.3, the savings are about 3 gallons or $9.

[Alexander]

I will be further devloping the cup holder in the next month when I will be getting a 3D printing machine and a 3d scanning arm.

I will also have a new Squarebird product that every Squarebird needs, since this part deteriorated to nothing on most cars.

[JohnG]

What is a 3D printing machine??

You mean you are going to keep us in suspense about the second item mentioned???

[Alexander]

The 3D printing machine can actually print objects in ABS plastic according to a design made in a CAD(Computer assisted design) program. The 3D scanner arm is used to take points in the real world and put them into a CAD program. You can reverse engineer parts or use it for measurements to make parts. In the case of the cup holder, I can get a very accurate measurement of the console to base the cup holder on.

[byersmtrco]

Last trip up Alameda, my 60 got 17.5
That was avr same speeds you mentioned, 65-70

A couple of differences mine has, is 3.00-1 ring and pinion (installed years ago) stock is 3:10. I have 15" whls which overall tire height is close to the same as the original tall stagecoach size that came with em. And I have the Edelbrock carb. I love these carbs. Mine needs to be gone thru. I suspect there is dirt in it. It's at least 15 yrs old (Prob the 1st Edelbrock Perf Carb ever made) Plus, it was dialed in to the old motor, which had the smaller combustion chambers, stock 390 bore and a different cam profile. So it doesnt run quite right. I'll dial it in though. I'm shooting for 18-19 freeway mileage.

[JohnG]

John, do you have a sense of what the changes in rear end and tires did to your RPM at highway speeds?? I will have to be honest here and admit I don't know what RPM a TBird cruises at 60 mph at. 1500? 1800??

Many years ago I got some substantial gas mileage gains in a motorcycle by putting a smaller rear sprocket on and thereby lowering the RPM by about 10%.

I believe the basic idea would be that every piston stroke has so much friction associated with it (which is wasted energy) and therefore by reducing the RPM one is reducing the friction generated. Not to mention the heat generated by the automatic transmission.

John

[byersmtrco]

300's to 310's isn't that much of a difference. Maybe 100-150 rpm. When you go from 373's to 308's (those are GM ratios) then you see a difference.

If/when I need to go thru the 3rd member, I'll prob go to 2.91

My tires even though they're 15's are still too low of a profile.
I plan on going from the 205-70-15's to 215-75-15. That's about an inch taller. The 65 TBird had those size tires. I had to use the spare. The diameter was right. Filled those big ol wheel wells right up. That will drop eng rpm as well. 1" taller makes a diff. Then I'll just have to figure out the speedo error.

[Guest]

These things are what they are. To get better miles the best solution would be a 325 rear and a overdrive trans.But how do we bolt that up?????

[byersmtrco]

Well . . . that's do-able. Go C6 trans and add on a Gearvendors overdrive unit(takes the place of the stock tailshaft) With that, it would actually be a 6 speed. 3 direct and 3 over (the best of all worlds for around town acceleration and drop her in O/D on the freeway and tach 2200 @ 70 mph (=20+ mpg . . . prob 25)
It's all controlled by a switch. Cool sh__!!! And bulletproof too. They were putting them in motorhomes 20 years ago (Before the days of AOD's & 700R4's) They'll handle as much horsepower as you can throw at em.