From 13.5 to 17 MPG with an Class B RV

[slowmover]

On that 454-4V above. The Rochester QuadraJet can be tuned to provide excellent mileage. Don't know if yours is the feedback style (electronic carb) or the older all mechanical type (with which I am familiar), but the latter can be adjusted for best cruise/part throttle separately from the other operating systems. See Doug Roe's book on the carb.

BANKS makes performance part which essentially aid efficiency, as does EDELBROCK. Best starting point is to fuel 'er up and take it across the weigh scale for a certified reading. You'll also want rear gear ratio, transmission type, tire height (see manufacturer numbers), intended cruise speed or rpm, and get some cylinder compression readings to go with it in order to get good advice.

See also HOWELL Engineering for TBI retrofit. If the engine still has good -- and even -- compression, then a free-flowing single 3" exhaust after the motor will make the most of what you have.

7-9 mpg is about what is to be expected. 10 mpg is almost impossible. But with numbers this low it is all about percentage increase.

[hansj3]

fuel injection is not really that hard to install on an older chevy. used tbi units can be sourced cheap and do really help. the hardest part is getting them to work with your application, for example

my friend bought a jeep grand wagoner. it routinely got between 7 and 9 mpg, no matter how hard he had his foot into it. long story short, we found out some one had swapped the 360 out for a 401..... but we took a tbi system out of a 92 1 ton truck found an adapter plate and adapted the sensors, and it is a really sound truck. starts year round, it now gets a solid 14 on the highway and seems to get 10.5 in town. everything was off of a 454, it also gained a hell of a mid range and kept the low and upper it had before.

now i dont know how much can be attributed to the fuel injection or if the carb was sized or tuned wrong, i never saw the carb, but the easy starts alone were worth it. we skated away with everything for $250. that said for you it might be even easier. like take the whole manifold and bolt it up and everything after that might be plug and play

[trooper Tdiesel]

i remember are one-ton flat bed before we up-graded it.

most RVs ive seen have a simaler engine/trans/gearing set up.

it had a 7.5L460 4V 850CFM, 3sp c-6 auto trans, 4.10 gears and 235/85/16 tires, making for 3,000 revs at 60 mph, just under 8,000lbs empty granted i admit its MUCH less aro drag than a RV

swaped it for a 4.9L I-6 2V 350CFM with free flowing intake and headers with a granny 5.75-1 and a 0.75% O\D ZF 5sp, still same tire size and rear end.
empty weight of the truck dropped to 7,250lbs yea we put the truck on a diet and it lost 600/750lbstake that weight watchers

dropped rpms to near 2,000 at 60 and saves big time in how many sets of front brake pads the truck goes thru having REAL HOLD BACK power with the truck up at its 16,000 GVW

oh and went from 3 to 7 mpg, 8 if its shout down in N gear for a long time LOL
to 7 to 13 that was a massive savings for are pocket book
i was halling off road one time though and i figure i was under the 7 mpg but i was moving 5 ton loads