The biggest thing you can do to help a 440 is slow down the RPM either by reducing speed or gearing higher and locking the converter, higher gears don't do much if you just slip the converter more. If your building a motor than run as much compression as you can get away with, enough compression to require premium fuel helps MPG enough to cover the extra cost in fuel, any tricks to permit more compression helps also like a source of fresh not underhood air, air gap style intake with no crossover, tight quench with closed chamber heads, fully radiused and polished exhaust valves, sodium filled if you can find them, ceramic coated exhaust under the hood retard cam timing a few degrees. An 850 thermoquad (800 gets into the secondaries too much even cruising) done by someone who really knows how to tune it will do better than a holley. Very little if any cam overlap and as much lift as possible heck some 1.7 rockers on a stock cam would work great. Well tuned spark timing (they like a lot 20 idle, 40WOT 50 or more cruise). Run a 3 angle valve job on the intake to break up fuel droplets.
I know I will get flack from old timers on this but I used to always try to run smallest ports I could find for my MPG motors but eventually found out it didn't help in reality and just killed any chance of getting a few RPM out of a motor (probably the only reason they ever APPEAR to help is you CAN'T turn any RPM), actually the opposite as I have hemi heads that flow 330CFM on my 2011 ram and it can get 20 on the highway empty. I would even run a maxwedge port on that and the longest runner, matching intake manifold I could find.
Some good ideas but just a couple points.
Gearing higher in my rv build will be done with gear vendors od. I am not so sure about using a lockup converter for heavy RV or something that is towing heavy loads. I have not been able to locate a gas unit with more than a single clutch. There are modern converters being built now that stall at 1100-1200 rpm behind a 440. I think that is a better choice in terms of durability.
I am building a 440 six pack pistons near zero deck, 413 closed chamber heads with sodium valves from ma mopar. Will work out to right at 9 to 1. At least 2 points better than from the factory. Not sure what gas prices are in your area, but 93 premium here is about 70 cents higher that regular 87 at about 2.20 a gallon. When stuff was only 20 cents a gallon more, I could see making up the difference in cost. I don't see any way to make up a 30% higher fuel cost though.
Agreed on the 850 thermoquad to try to run on the primaries as much as possible. All big block intakes are "air gap" design. Maybe I should fit a tunnel ram under the doghouse?
I will get the thermoquad dialed in using a wide band O2 sensor. I think I am going to put a bung in each header tube to be able to measure what individual cylinders are doing. Might be time to play with some epoxy and popsicle sticks. I know I can't get it perfect, but can at least prevent a too lean condition in one or more of the cylinders. I am going to send the headers to get jet hot coated after fitting and welding the bungs.
On a carb build, wouldn't oversized ports make for lazy flow, poorer mix, increased chance for detonation, and less throttle response? The 413 heads have small block sized ports- intake is a little taller than the intake port on a EQ head I have, and small 1.88 / 1.50 valves. Your hemi with multiport injection is an entirely different animal.
I'll be running a modern profile cam Mike Jones designed just for the 440 motorhome engines. 112 centerline, duration at 202. but .455 lift with 1.5 ratio and only 40 degrees overlap at the seat, and -19 at .050. Just my two cents, but I would rather spend the money on the cam than the rockers.
Dual snorkel cold air, polishing piston tops, chambers, and valves will be done. Heat is the enemy running a big block in an RV. Plan to run some electric fans, a triple flow radiator, and aluminum intake with the crossover blocked to try to keep it cool.
