The Big Block 440 upgraded to an Edelbrock Multipoint fuel injection system in my coach averaged about 7.5 mpg. It had to wind up to 3500+ rpm to pull 6% grades at 45 mph. Not a bad unit and I weigh about 14,500 lbs.
But I got a hankering for a diesel engine that wouldn't turn as fast and would have more torque.
So I changed my coach from the 440 with a 4 spd Allison to an '06 Duramax diesel with a 6 spd Allison.
Now note that I just changed the engine and the transmission. I didn't change vehicles (because I liked my vehicle!) so any changes were the result of just the engine and transmission - nothing else as nothing else changed! Size of vehicle stayed the same, air resistance stayed the same, and the driver stayed the same.
What happened to fuel mileage? Well it went from 7.5 to a documented 14.8 over 7,000 miles which included multiple mountain crossings out here in the West.
What happened to pulling power? Well, it went up as measured by being able to pull 6% grades at 65 mph.
What happened to sound levels (note the coach was always a rear engined unit)? Well, the sound level went down mainly due to operating at lower rpm. With gas I pulled the 6% hills at about 3,500 rpm and with the diesel I can pull that same 6% grade hill at 2,200 rpm. Cruising rmp with gas was about 3,200 rpm and with diesel it is about 1,700 rpm.
Bottom line, I like the new configuration and am glad I did it. Its diesel for me. Forget the Big Block gas engines. It is either a turbo gas engine or a turbo diesel engine.
