gas mileage ?? HELP!!!!!

ferryboatcaptai · 11-01-2009, 07:38 AM

new to this site, my 66 shortbed gets 14 miles to the gallon, i have the 250 with a 1 barrel carb and a 350 turbo tranny , 3;73 rearend . any one know how to improve my mpg . what about changing to a carter carb??
i drive my truck 70 miles a day and it runs great, but the gas is costing me alot. FBC

markeb01 · 11-01-2009, 02:52 PM

Probably the biggest bang for the buck is changing the rear end gear. Even a 3.50 would be an improvement, but a 3.20 would probably be more ideal. I faced the same exact problem years ago, when I commuted 70 miles a day in my 1960. I switched from a 3.70 to a 3.08 and it made a huge difference in mileage, but I had a 350/350. A 3.08 behind a 250 six might be too high a ratio. The performance around town might really suffer. At freeway speeds if might be ideal, or it could cause the engine to work too hard by not allowing it to spin fast enough to make its best torque.

drabo · 11-02-2009, 11:46 AM

Consider a 700R4 swap. That extra gear makes a big diffrence.

markeb01 · 11-02-2009, 07:07 PM

In addition to the extra gear, the 700R4 .70 overdrive will really drop the final drive ratio as well, if you want to swap to an automatic.

drabo · 11-03-2009, 09:58 AM

The only problem with a rear gear swap is you are going to have to change out the carrier plus the gears. With just the tranny swap I dropped 1400 RPM at 65MPH. I also started with a TH350 tranny and not a powerglide.

66 KUSTOM · 11-03-2009, 06:10 PM

70 miles a day? how about a honda or toyota?

drabo · 11-04-2009, 08:46 AM

66 Kustom this is a public forum and I must ask that you refrain from using any foul language. My kids could see this and be scarred for life.

66 KUSTOM · 11-05-2009, 04:40 PM

Quote:

Originally Posted by drabo

66 Kustom this is a public forum and I must ask that you refrain from using any foul language. My kids could see this and be scarred for life.

hahaha, thats hillariouse!!!!! to funny man, sorry, ill watch what i type. No more foriegn words from me!!!! in my defence i will admit it has been several years since ive owned a foriegn car. (besides dirtbikes but theres no US manufacturers for those)

11-01-2009, 07:38 AM	#1
ferryboatcaptai Registered User Join Date: Nov. 1, 2009 Posts: 1	gas mileage ?? HELP!!!!! new to this site, my 66 shortbed gets 14 miles to the gallon, i have the 250 with a 1 barrel carb and a 350 turbo tranny , 3;73 rearend . any one know how to improve my mpg . what about changing to a carter carb?? i drive my truck 70 miles a day and it runs great, but the gas is costing me alot. FBC

11-01-2009, 02:52 PM	#2
markeb01 Registered User Join Date: Sep. 29, 2009 Location: Spokane, WA Posts: 26	Probably the biggest bang for the buck is changing the rear end gear. Even a 3.50 would be an improvement, but a 3.20 would probably be more ideal. I faced the same exact problem years ago, when I commuted 70 miles a day in my 1960. I switched from a 3.70 to a 3.08 and it made a huge difference in mileage, but I had a 350/350. A 3.08 behind a 250 six might be too high a ratio. The performance around town might really suffer. At freeway speeds if might be ideal, or it could cause the engine to work too hard by not allowing it to spin fast enough to make its best torque. Last edited by markeb01; 11-01-2009 at 02:55 PM.

11-02-2009, 11:46 AM	#3
drabo Registered User Join Date: Jun. 9, 2003 Location: Patrick AFB, Florida Posts: 649	Consider a 700R4 swap. That extra gear makes a big diffrence. __________________ 66 Chevy C10 "The Nugget" 283/700R4

11-03-2009, 09:58 AM	#5
drabo Registered User Join Date: Jun. 9, 2003 Location: Patrick AFB, Florida Posts: 649	The only problem with a rear gear swap is you are going to have to change out the carrier plus the gears. With just the tranny swap I dropped 1400 RPM at 65MPH. I also started with a TH350 tranny and not a powerglide. __________________ 66 Chevy C10 "The Nugget" 283/700R4

11-03-2009, 06:10 PM	#6
66 KUSTOM Registered User Join Date: Jan. 11, 2005 Location: SALEM OR Posts: 580	70 miles a day? how about a honda or toyota? __________________ 66 KUSTOM

11-02-2009, 07:07 PM	#4
markeb01 Registered User Join Date: Sep. 29, 2009 Location: Spokane, WA Posts: 26	In addition to the extra gear, the 700R4 .70 overdrive will really drop the final drive ratio as well, if you want to swap to an automatic.

11-04-2009, 08:46 AM	#7
drabo Registered User Join Date: Jun. 9, 2003 Location: Patrick AFB, Florida Posts: 649	66 Kustom this is a public forum and I must ask that you refrain from using any foul language. My kids could see this and be scarred for life. __________________ 66 Chevy C10 "The Nugget" 283/700R4

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