3:55 gears to 323 gears

On another note
But honestly, the biggest hindrance to fuel-economy is not having enough ignition timing, and or having the exhaust valve open too early, made worse when both are in effect; and/or operating in the wrong rpm for the specific cam.
All the math in the world goes right out the window, when trying to make a 292 cam operate at 1600rpm, it will just spew unburnred gas into the headers, and if/when it catches fire in there, it will make it all the worse.So some common-sense has to prevail.
Generally, I have found 2200 to be the lower limit of a hot street cam, and the engine will want more ignition timing there, than is generally possible to give. Mine has liked up to 60 degrees there.How can a guy meet that need? No stock or modified parts can achieve that. At the best; if you cranked the mechanical to 38* and modded your Vcan to get 22*, there is your 60*.. But just try and drive that hummer at 2200 at WOT, with 38* of lead. Furthermore; what will the idle timing be with such a set-up?, and what will be the idle-speed? Yur not gonna successfully marry this tune to your street engine. You will require a stand alone timing computer.
If you don't give the engine the lead it wants a cruising speed, fuel-mileage will suffer.

It's all about maximizing the cylinder pressure at just the right time of crank-rotation, to maximize the energy-transfer of the expanding exhaust gasses, to the crank and to the rear wheels following.
So the key player to good fuel-economy, is the running cylinder pressure, at cruising rpm..

This is how, the stock lowly LA318 can make fuel economy with it's atrocious sub 8/1 Scr and subsequent meager cylinder pressure of barely into the 130s. With 2.76 rear gears the rpm mathes out to 65=2230 in loc-up. The peak efficiency of that LA comes at about 2400rpm.
That 318 cam has specs of
240/248/112+4/Ica of 48*/132comp/120power/ Effective overlap of 16*
Check it out;132* of compression from an Ica of just 48*. That traps a lotta aircharge, preventing it from backing up into the intake. The meager overlap means very little,if any, exhaust dilution. But the thing I really want guys to see is the 120* of power extraction. That is a lot! And by the time the exhaust exits the chamber, there is not much energy left in it.
If you get the ignition timing right, you can impart a lot of pressure to the short 3.315 stroke, which will be down to 2.89effective. The cylinder pressure is expected to be 140 at sealevel, with a VP of 116.
VP of 116 is what most of us are used to seeing/feeling with our 318s, and more often than not , with 2.76 rear gears. We know how that feels; albeit with a 2bbl and single exhaust.
If you assume a 7/1 pressure rise, due to heat, then one could expect a new engine with 140 x 7=980 pounds of pressure at WOT from this engine during it's peak efficiency. That's not bad.

But if you bump the Scr to 9/1, then the cranking cylinder pressure might rise to 160psi, and at the same 7/1 expansion ratio, this now mathes to a potential of 1120psi at WOT; a 14.3% increase. As to torque, this is like an across the board increase of 14.3% in rear gear or from 2.76s to 3.15s. Or in terms of peak power, about 20hp.
Now that is something; same engine, only the Scr was increased.
But what is the first thing a newbe says? He says; "not taking the short apart". And most of the time that 40 year old engine is still on the original rings! With gaps you can drive a truck thru, and the rings are coming into the hole under the ridge and spewing compression straight into the crankcase. You know; 980psi leaking thru that monster gap.

So he puts a too-big cam in there, and the cylinder pressure falls to 120 , and 120x7=840 running at WOT, so the torque has fallen to 86% so it feels like the 2.76s have turned to 2.37s ....... and here he comes with "what do I do now?", and the only solution is a higher stall and bigger gears.
In the meantime, the fuel economy is so low, he dares not drive it anywhere.
To my thinking this is a ridiculous thing to do.
If I wanted performance from a 318, the very very first thing I would do is bump the pressure up. And that is what the factory finally did when the 5.2M came out.