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LONGHAIR · 09-01-2008, 09:54 AM

In theory the fuel usage is directly related to horsepower, meaning that you can only get so much power from a given amount of fuel...and under perfect conditions. So, again theoretically the cubic inch factor doesn't matter....now, you might have to be a bit more radical to get 300HP from a 307, but if the horsepower is equal, the fuel used should be similar. Of course this is all sounds good, but in practical application?

Mileage is more about the efficient use of that power. You can only push a brick wall with a certain degree of efficiency, and 300HP is more than enough. These trucks are heavy and aerodynamically huge, efficiency was not a concern when they were designed and there isn't much that can be done about it at this point.
Low-end torque to get it rolling w/o a lot of throttle, proper gearing and over-drive....along with driving style will get you the best you are going to get.
The milder 350 would probably drive better, more torque with the longer stroke.
You can squeeze some more out by eliminating some brake drag/rolling resistance and a manual transmission, still with overdrive. The cost of all off this might take a long time to recover though.

09-01-2008, 09:54 AM	#4
LONGHAIR just can't cover up my redneck Join Date: May 2004 Location: Columbus OH Posts: 11,414	Re: 1972 chevy 1/2 ton 307 In theory the fuel usage is directly related to horsepower, meaning that you can only get so much power from a given amount of fuel...and under perfect conditions. So, again theoretically the cubic inch factor doesn't matter....now, you might have to be a bit more radical to get 300HP from a 307, but if the horsepower is equal, the fuel used should be similar. Of course this is all sounds good, but in practical application? Mileage is more about the efficient use of that power. You can only push a brick wall with a certain degree of efficiency, and 300HP is more than enough. These trucks are heavy and aerodynamically huge, efficiency was not a concern when they were designed and there isn't much that can be done about it at this point. Low-end torque to get it rolling w/o a lot of throttle, proper gearing and over-drive....along with driving style will get you the best you are going to get. The milder 350 would probably drive better, more torque with the longer stroke. You can squeeze some more out by eliminating some brake drag/rolling resistance and a manual transmission, still with overdrive. The cost of all off this might take a long time to recover though.