What makes a engine efficient???

[Ziegelsteinfaust]

I am completely lost, but I am happy it is better.

Also on the I am very happy side is my truck with 10.5-1 compression now runs great on 89 octane. Testing with 87 will happen when I get around to it as I am burnt out on carbs right now.

My rcsb has 4.88 gears, a TH700, and 30x9.5x15 AT tires.

Previous motor was a 383 LT1 with 500 lift 206 duration 116 lsa cam. Rough specs as I do not have the cam card.

New 350 LT1 has a comp 306 cam 510/540 lift 230/244 duration 112 lsa.

They share the same 1 3/4 headers, GMPP LT1 4 barrel intake, same 750 VS Holley, and transmission with 2500rpm stall converter.

So the 383 got 6-8 mpg city, and 18-19 mpg highway at 75. Pretty routine as I drive the engine for a few months.

After I figured where I went wrong on the Holley. My 350 does 10+mpg city, and 18 mpg highway at 75. Preliminary results based off a some quick testing, but I drove 30 miles city, and a quick blast to Apple Valley to drop something off for my BIL.

So anyone got an idea why my mpg went up with a wilder cam in the city?

Was it some cam magic inside specs that I am completely missing?