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Old 09-06-2012, 11:55 AM   #19
Edahall
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Join Date: May 2011
Location: Goliad, TX
Posts: 672
Re: Increased MPG for carbs?

Quote:
Originally Posted by OSE_NERO View Post
I'm still optimistic that there is something out there that can break 18mpg for us "barn doors".
Well it is possible to hit 18 mpg on a carbed truck. My 1972 GMC, 1/2 ton, 4x4, 350 cu in, did even better than that and that was in the early 80's. Here's the formula.

1. 3.08 gears
2. SM465 4 speed manual
3. P235/75/15 tires
4. SP2P Edelbrock intake manifold (small diameter intake runners)
5. Rhodes lifters
6. High lift / short duration cam
7. Quadrajet carb (leaned out for best fuel economy)
8. Carb spacer
9. Timing advanced
10. Water Injection
11. 55 mph

For even better fuel economy, I would use Vortec heads so I could run more compression and more timing advance. The Vortec heads should be good for an additional 1-2 mpg. Also, for highway driving, 2.73 gears would even be better.
__________________
1990 ¾ ton 4x4 Chevy Suburban
-Cummins Diesel - 12 valve - factory rebuilt
-6 speed bullet proof manual transmission - NV5600
-Gear Vendors Overdrive - HX35 Holset Turbo
-NP205 iron transfer case
-3.73 gears -2" Lift
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