Hi,
Youtube entertained me with the stories of a guy that loves Winnebagos, and putting LS engines in them, with turbos. I think one of his Winnebagos was a Chrysler 440 before, so he has no fear of projects.

https://www.youtube.com/watch?v=LC-pfi_NB5Y

He took one of his machines on the "Hot Rod Power Tour", and his review of his work on his latest rig has some good ideas. He talks about (40 second mark) using the hydroboost unit from a late model Chevrolet 2500 truck and making his brake power improve nicely. I have to consider that.

He also talks about getting his AC system working. His talk makes me think that I have replaced everything mechanical on my rig, except for the heater core. Guess what I need to do for preventative maintenance????

Here is 2 minutes from Holley and a review of a twin turbo 6 liter LS in a 1972 Winnebago, with Holley control computers. Awesome stuff!

https://www.youtube.com/watch?v=LtjZ8VukTEI

MORE POWER!
Matt

I guess I am just too old fashioned. Coming from the days where "there is no replacement for displacement" I would avoid the high tech dual turbo systems. Turbos work great at high rpms but do little for torque. For top speed turbos are great but for low end torque, not so much.

Considering the modifications needed to completely swap out a driveline, along with exhaust, wiring and sensors, I would opt for a much simpler solution, as I did with my Regal. I stayed with the 454 big block. OEM engine was 8.0 to 1 compression, minimal cam and carburetor, EPA rated only 240 hp.

I ended up replacing the engine. Same 454 displacement, forged pistons, forged crank, 4 bolt mains, roller cam lifters, dual row cam chain drive, bigger valves, more cam and TBI fuel injection. Compression was 9.5 to 1, still okay with pump gas. 438 hp! If I had not replaced the engine, I still could have had everything but 4 bolt mains.

As it turned out the cam was a bit much for a heavy vehicle so I went to a 502 torquer cam. Down to about 400hp but just about perfect. Pulled like a train all the way to 80+ mph.

The TBI ran really well and in spite of the power increase I still got better mileage. OEM was about 6.5mpg. I was getting 8 when I sold it. Really fun to drive, too!

No exotic exhaust routing and doghouse heat for twin turbos.
Minimal changes to the chassis and driveline. No custom wiring, mounts or brackets. No compromises for reliability and longevity.

I know the grass is always greener on the other side but I would not give up on our coach machinery until it was tweaked to modern performance standards. They have good bones and can be built to run strong and simple.

If I did swap again, I would still tend towards larger displacement, ie 502. Just drop in a stroker crankshaft and rods. I see no future for turbos in heavy vehicles like motor homes.

I drove over 40,000 miles with my Regal. I have 39,000 more on the Monarch now. I wonder how far those gearheads drive their hotrod coaches. I would rather be driving my coach than constantly working on some latest experimental upgrade. Just sayin'

I will add to Steve's excellent review of engine replacement.

A motor home needs TORQUE! Low RPM TORQUE! I have done many LS1-Ls6 conversions, but only in cars! These conversions were in vehicles that are less then 4000 lbs and of course a very small frontal area.

Further I could easily change the gearing to maximize the acceleration and or high speed goals for that particular conversion application. Here is where converting a RV get complicated!

From the lightest RV ~10,000 LBS to ?? That is a load that is always being moved from dead stop to 55 >+/-. That takes torque, going up a grade takes torque! Towing takes torque! If you are geared for high HP engines it will not be optimum for RV applications and fuel mileage will be lower. Older 454 (and 350) RV applications used carburetors and all kinds of emissions equipment. Not very well suited for the demands of RV power and long life.

Wear and tear, will always be higher in high RPM engines. A 454 Chev engine will have torque to move the RV at a reasonable rate and still be geared to move along at highway speeds. BUT, It would not last as long as a small diesel of similar ratings. Very few 454 Chev engines in RV applications lasts much longer than 200K miles if that long! Older RV build RV use higher rear ratios so the engine spins faster and has a higher power (HP) rating. Newer RVs are designed with overdrive transmissions and fuel injection to lower the operating RPM and improve fuel efficiency. All good for gas owners but not early RV models!

Diesels? Another subject. The diesel world is the trucking world and of course the bigger RV world. Yes I am a Diesel RV owner and I am biased. My first RV was a 454 Chev powered with overdrive and fuel injection. On as good day keeping my speeds under 65 MPH I would get 7.5 - 8 MPG, no hills or significant grades. Engine lasted to 150K miles, transmission lasted to 95K miles.

Now since 2006, I am a Barth 30' Breakaway owner, originally a 5.9 Cummins 230HP/500 LBS/Ft and Allison 6 speed. 320K miles and first overhaul of the 6 speed (another story) at 350K replacement of the engine (another story). 5.9L Cummins 375 HP/1100 LBS/ft (Dyno tested in place). Mileage has not changed appreciably Towing and grade challenge, GONE! My average fuel use for 350K I averaged 10.12MPG. I am a full throttle guy, I drive 70MPH-75MPH anytime I am on freeway outa the left coast. Tires are rated at 75 MPH, my limit.

MY advice for what it is worth.
If you have or buy a gas 454 rig, if needs to be replaced, only replace it with a 454 WITH fuel injection, look into replacing the trans with a 4L75E overdrive trans and Change the rear end gears to a higher number to improve acceleration and with the OD your engine RPM will be lower, FI will improve the overall engine management.

If you get a RV with a Chev 350 engine, if you are happy with the performance and economy, replace it with another 350 Looking to improve performance go to the above and replace drive line with a 454/OD transmission. One can usually find 454 for the same money as a 350.

If you are Diesel Breakaway owner or potential owner again, IMHO!
4 speed Allison transmission are just OK. They need constant attention for overheating and adjust your driving habits to minimize trans temp!
If you are considering changing the transmission to an overdrive unit such as a Allison 2000,2500 or MD3060, keep in mind that the lower gear ratios are almost the same as the 4 speed Allison. You will have no noticeable change in acceleration or towing power. Yes you will have a higher cruise speed but getting there will take time and you may experience a lower MPG as operating at or near 2500 RPM is in the de-fueling range of the engine.
The Barth Breakaways with 4 speed Allison transmission came with the Dana 80 rear end and at that time the highest numerical ratio for that case was 3.73. To get better acceleration and towing the rear gears need to be > 4.1:1 or higher. Then one would realize the benefits of lower gear acceleration, final gear speed and lower engine RPM.

I know this is long, BUT I guess what I am trying to illustrate is, is you find a RV, Barth or SOB, if it fits your use, your budget, get it! Older RVs are not ever going to be a flip project to make $$$$ but do what you think is best for your usage situation and your enjoyment.

Please understand this is just my humble opinion. If I (we) can help in any way let us know your issues.

HTH
Ed

Ed,great summary, I will add a second to torque is your friend and FI beats carb. Figure a boat is like a coach always going uphill and against the wind, 1mpg at hull speed (10-12mph) is the norm with carbs. A friend with essentially the same boat as mine repowered with modern 8.1L FI engines and jumped to 3mpg at 25 mph. The question I have for the future is the lifespan of these newer high output small diesel engines.
Being a geezer I believe there's no replacement for displacement, example that 8.1.

absolutely correct. I looked at some follow-on videos and there is clearly a HUGE difference and benefit to the use of the big block engine below 3K RPM.
Matt