The important advantage of FI is not fuel economy, but longevity & reliability.
1] The instantaneous engine starts (no choke problems)
2] Instantaneous altitude adjustments
3] No cylinder washdown in cold/rich conditions, as well as at idle
All of which adds up to "like new" performance for tens of thousands of miles longer than a carb'd engine.
some better fuel economy.
Ironically, the better FE is much the result of warm-up and adverse climate/terrain advantages accruing to the FI systems. The on-road, level Interstate FE difference between FI and a well-sorted QJet is low (that's a great carb). But the tenths really add up on a heavy vehicle.
I understand the OP's concern about the difference between hot rodding and RV performance. I spent more than 30-years searching the details in countless articles, advertisements, etc (for CHRYSLER motors, in main).
A 454 is a half-decent big block. A good ways down the list from the ones better designed (the Ford 460 was the best, the older 440 Chrysler would have been second; the 454 lacks the deep skirt and mains reinforcements, poor rod/stroke ratio, bore/stroke ratio, etc), but the huge aftermarket makes building one to any sort of spec the easiest and cheapest. The advantage to Chevy having built the most big motors.
The limiting factor isn't simply weight, but the low compression ratio needed to accommodate a motor always on the verge of detonation. That limits what camshafts can do. One would do well to read up on dynamic
compression ratio for a deeper understanding.
In the end I never saw that any more than a true
compression ratio of 8.8:1 was realistic. Even with the best heads and head work (that's where the power -- and money -- really are) there are reasonable limits on cam duration. But cam lift
for an RV roller
cam can be quite high (relative to flat tappet cams).
Maximum torque numbers always sound nice, but the torque profile (dynamometer readout) that comes in early and stays late
is the way to go, IMO. May not have the high peak of other types, but power in a moho is about power recovery after the shift. One cannot rev so high as with the hotrodders, so the point at which the engine "comes back in" (rpm) after a transmission shift is completed, is vital.
One must work from a cam builder sheet:
- Tire height
- Drive axle ratio
- Torque converter slip
- Transmission gear ratios
- Vehicle weight
- Anticipated road speed
These are the limits. The camshaft that works with the limits is the one to have (and custom cams can be done, almost a requirement for cylinder heads properly "flowed" for low and middle range power [backcutting valves and proper seat flow a huge
improvement; percentage flow gain at low valve lift]).
The engine built or modified with this in mind is more easily fitted by formula. Fuel delivery must work with primary and secondary ignition advance
(this is where most attempts fail, as finesse is involved; both science and art. Luckily, dynos can capture problems and suggest solutions when exhaust gas monitoring is done).
I'd copy the intake and exhaust of the BANKS offerings, overall. Packaging is always the problem on engine air intake and exhaust. An infomative article on the latter (by David Vizard, anything he writes is gold, and for our purposes, the best data laden) Auto Exhaust Science
The rest will take some work. For example, a cold thermostat is the wrong way to go. I've changed to hotter ones (185F to 195F) and found better FE as well as better all around performance. But one must search out the best water pumps, radiators, etc. Shrouding and air flow control. Fan clutch data. Fan pitch. Etc.
Start with a weight scale ticket representing total moho weight as well as side to side variances; then on to individual wheel position. Correct any large weight imbalances and look to the springs, suspension bushings, etc, before
any power additions (as these can, literally, suck up a lot of horsepower; power not properly transmitted to the ground). A good set of anti-roll bars is worth horsepower, as are best shock absorbers (KONI FSD) as a vehicle faster in transient steering response will burn less fuel, will require a bit less horsepower, etc.
A sloppy transmision is inexcusable. Have it tested out per the FSM as the second round of things. Setting shift points correctly is worth every minute of work. And good firm fast
shifts are important.
Brake drag, steering wander and alignment are next. Less than perfect is unacceptable. The A/S moho sits on a crude, wandering & wallowing chassis. Make it work!! The world of big trucks pays more attention to fuel economy than any other sector. All of the above [non engine] is straight from that world.
The 454 engine, and cam, are literally the very last things
. . . .