Your original post had a question about overheating. Workhorse ran thousands of miles worth of tests in the desert. The engines from those tests were sold on Ebay a few years later, as good running engines. I did end up talking to them about the engine at the time. There were no problems with overheating.
What seems strange is that the water should be really hot within 45 minutes of running. You can buy a new thermostat, but it seems strange that in 45 minutes, the water is not really hot. I realize an IR gun is about 10 bucks more than the thermostat, but a IR gun is very handy to have anyway. It would be nice to know what the temp is right at the thermostat. You could touch the tank there and see if it is hot, as you said your water is only luke warm at best. If I understand correctly, it did not take much water flow before it turned cold, which doesn't seem right either.
While GMC built the drivetrain and SHELL, Coachmen Industries (Coachmen RV company) actually built and installed all the interiors in the mid 70's in Elkhart, Indiana. I would be more concerned about the Air ride system and cost and availability than any other drivetrain parts. DougAlso some units were upfitted by Avion.
As far as air ride, for one that is handy, there are several options available. There generic parts that will work, or there are some well thought out solutions. That is why if you own one, you belong to an affinity group, with a wide variety of ideas, and the resources to back them up.
To the OP, for the things you mention, you could look at Revcon. There is a version as short as 28ft with a permanent bed in the back. (sometimes called 27 ft Duke) In the 80s the drivetrain is custom, but built mostly from common parts. The interiors were very high end Wilsonart laminate, so they hold up well. All very light weight and super strong. And just think what you could do to the motor...
You might look into the POR-15 Fuel Tank Repair Kit
Don't waste your time and money. I used that product, followed their complete instructions, yet the stuff flaked off the inside of the tank the first time I used it. Went through several fuel filters on one trip, just getting the fuel in the tank used up. So a tank that could have been repaired was ruined.
As a result, I searched a very long time for many different options. I finally found a pair of 40 gallon tanks that I was able to make work. I ended up buying them from:http://greatlakesskipper.com/catalogsearch/result/index/?dir=desc&limit=200&order=relevance&q=fuel+tanks&x=0&y=0. Because they were within driving distance, I drove up to Wisconsin on a Saturday morning and picked them up. Saved a bit on shipping. They ended up waiting for me to get there. Nice people, so if they happen to have a tank that will work, they are good people to buy from.
Since the tanks are plastic, I welded up a frame to carry the weight. No more leaks. The only thing you have to watch for is making sure you choose the correct pickup outlet. The pickup has a check valve, and does not work very well for a return line :).
A few years back there were news reports of government agency night time flyovers with IR cameras. What they were looking for was to create a report that the fire department could use, so when they entered a house during a fire, they would know where the occupied bedrooms were. Did it actually happen, I have no doubt in some areas it did. Is it happening now on a regular basis? With most city governments strapped for cash, this seems very unlikely. Those kinds of things happen sporadically, we know of periodic reports of government flyovers resulting in zoning violations on private property.
While it is not happening currently, I have no doubt it will happen much more often in the near future with drone surveillance. No doubt with local city governments jonesing for power, they will be all over that intel.
Last thing I would do is spray the metal parts with ATF, my way of doing a poor mans rustproofing job. I never felt like the garage would take as much time as I did. I wanted to feel confident when I was outside of my home area that everything was in top shape prior to leaving.I thought that was why you not supposed to repair broken seals. I made the mistake of installing a new trans and now my front end is starting to rust. :(
Take some pictures even if you don't buy it, just for fun.
Take a good look at the door fitment and the wall where it meets the door frame. Make sure it is not spreading. I looked at a GMC to buy many years ago, before I bought the Revcon. The GMC had grown fat in the middle, which meant the door did not fit, and the interior wall had pulled away from the door frame. I have since learned that problem is not completely uncommon. There are ways to deal with it, but something like that should be significant leverage against the price. Inspect the walls around the windows for leaks/rot. Inspect for frame rust. On that age of unit, the potential for large amounts of frame rust is pretty high. All those things differentiate it from a premium restored vehicle.
The problem with pricing a GMC is 2 fold. There are a ton of units out there with very high price tags on them. This has driven the market artificially high, even for ones that are not restored. The second problem which was eluded to earlier is that any motorhome, regardless of the collector factor will never be worth what someone has invested in it. This puts dollar values all over the place and makes it very hard to find a stable consistent why to come up with real numbers. Of course there is also the issue of what something is listed for, compared to what people will actually pay. This range is rather wide, especially for an older unit that has been redone.
As far as the over all big picture, as a general rule, GMCs were much better at traveling than they were at camping. You have a 26 foot unit, that is laid out light on the amenities, and heavy on the number of beds - which was a common philosophy in the 70s. To be able to sleep 6 in a 26 foot coach, you loose space in other areas. One of the biggest is the bathroom. Most GMCs have a wet bath, which means you shower over the top of the toilet. Unless you are looking at a rear bath model, or one that has been modified, you don't have a separate shower. (yes there was the Royal, but they are rare).
As far as the engine and drivetrain, the 455 was a very durable engine as long as you didn't run high RPMs too often. I knew of a Revcon owner (uses the same drivetrain) who had almost 300,000 on the original engine and drivetrain. It would still be running today, except for a propane leak that ended the coach's life. The Revcons are lighter, so they don't put the strain on the drivetrain, but even so, the 455 was very durable, as long as you didn't wind it out. One heavy wear point with a GMC is the front wheel bearings. This is a high maintenance item. Not the end of the world, but something you just build into your maintenance budget and schedule. Other than the front wheel bearings, I do not believe the rest of the drivetrain is prone to wear any faster than any other motorhome, however when it does wear, the cost to repair is about 1.5 X the cost of a rear wheel drive coach. If you paying a premium for the coach, you need to know the condition of the front end, as that should significantly affect the price.
My personal opinion is that you are paying a lot for the wow factor, and not necessarily for the actual value of the coach as a functional camper. Sure wow is cool, or otherwise people would not own or restore antique cars. As a coach, it is a little better built than many of the coaches in that era, but its not some magical super high end unit. Unless a very significant purpose is collector driven, as a camper, it has its limitations.
For all the work I've done on my coach, I still take it down to the local quick lube joint. The cost is cheap and its convenient. I count the grease fittings and watch them do it. To get the ones on the axle, the coach has to be rolled, otherwise they can not be reached. Its a 2 person job, as one person has to be under the coach, so they can tell when to stop, so the fitting can be reached. I've been going there for over 10 years, they know me pretty well. Its has the cool factor, so they tend to be more careful than their average car.
This will give you decent transportation, so you can camp inconspicuously and are less likely to get booted out of public parking lots. The engine is Buick, so it should not be too bad if it needs worked on. While it may seem like you are buying a really small vehicle for the money, a Vixen will hold its value. It is going to be easy to drive, and gets about 20 mpg.
Incidentally I would recommend staying away from Fleetwood (ie Bounder, Pace Arrow) if you are looking at coaches from the 80s. While many brands coaches had delamination issues, Fleetwood products from that era will really bad for it. Delamination is where the outer skin delaminates from the luan (wood) backing. It is caused by water intrusion, which rots the wood backing. Usually the water will also cause mildew, as well as rust away the vertical framing. This problem is easily recognized by large blisters, or wavy soft spots on the side walls. Commonly seen around the bottom of the windows, although it can be from roof leaks as well. BTW: If a dealer tries to tell you that delaniation is no big deal (yes I've heard them do that) Slap him in the face as hard as you can for lying and then leave.
While I still believe my primary reasoning is still the non-baby boom, some minor factors are also the general break down/disruption of the family. When I was in high school, can only think of a very few people I knew who were from single parent homes. When I talk to my kids or their friends, a very high percentage are from single parent homes, or blended homes. This break up of continuity of family life is pretty significant. Most of the time this happens in the earlier years, so right after a divorce, the last thing on ones mind is camping. Pretty hard to do as a single parent, and pretty low on the priority list. Usually one is in survival mode. Camping takes thought and preparation.
What i would do, assuming you have some funds is go down to your local home depot or lowes. Look at the 2 inch foam board insulation. Buy a couple of sheets. Buy some fiberglass sheeting, and glue the sheeting to both sides of the foam board. Lay the foam board w/laminated glass on your roof and then use eternobond tape to attach the foam board together, which will also make them waterproof between the cracks. This is about the cheapest thing I can think of that will be structural and last, as well as being water proof. If the foam board has fiberglass sheeting glued to both sides, you should be able to walk on it.
To suggest that the main problems are imported goods from cheap labor does not look at the broader picture. There are many factors that have affected wages in this country. One's effective wage is calculated relative to one's expenses. One significant factor is the housing bubble. Housing cost is one's biggest expense, which has nothing to do with cheap imported goods. If your biggest expense has nothing to do with imported goods, it becomes very difficult to associate imported goods, as a significant factor.
Just looking at imported goods from cheap labor over simplifies the problem. "Facts" are not always what they seem.
IF you want to go on the cheap side, I use a 2Kw inverter from Horrible Freight. Bought it several years ago, and it will run anything I have needed it to, including the microwave. 150 bucks. The inverter is within a foot of the batteries. The shore power from the RV plugs into the inverter, that way all outlets are live. The only thing you need to watch out for is to turn off the converter and make sure the fridge is set to run on propane, otherwise you will run the batteries down pretty quick.
If it creeps up at idle, can you run the heater on full blast and have it keep up? If that helps substantially, then replace the radiator. If the radiator is so bad that it can't keep up at idle, but yet the heater will bring the temp right down, then you know for sure.
Most common radiator failure is coolant leaking to the floor...
Next is fins packed with crud...
If the fins are clean, coolant is flowing, the radiator pretty much has to cool.That was probably true with copper radiators, but most radiators are aluminum. They tend to corrode between the fins and the tubes, which may be able to be cleaned, but at that point, the fins have detached from the tubes. Once the fins have detached from the tubes, the radiator no longer works.
The best way to troubleshoot a radiator is with an IR gun. This will allow you to compare inlet and outlet temps, and confirm the radiator is doing its job.
The only other question I would have is if you are running FI or carburetor. If you are running a carb, you may need to consider if you are running lean at full throttle. I have seen where the mixture enrichment (power valve) was not working, so every time the secondaries opened, the engine leaned out and would overheat. FI can have similar problems, but it will yell at you if it does, which I assume you would not ignore.
Oh, and to actually answer your question, I would not be afraid of a recore. The cans on either end are much thicker and not likely to go bad. I'm going on ~8 years on a recore in my coach.
You might be interested in this site.
Yes, get to know Jim Bounds. I would suggest reading the daily pose, and even going back into the archive. You will get to know how they deal with many of the unique issues with GMCs. Lots of pictures describing stuff. From everything I have read, there are probably 3 issue to look at first.
1) Frame rust can be a big issue, especially around the rear boggies. If its not bad, then its worth the effort to keep going, and invest in the rest of the coach.
2) Before you drive it very far, Repack or replace your front wheel bearings. These are a high maintenance item, as they are somewhat on the small size for the load. Spindles are getting scarce, and the last thing you want to do is take a chance on spinning a bearing. At the same time, you will likely replace the A-frame bushings, although it won't prevent you from going down the road like a bad bearing would.
3) Take a look at your entrance door fitment. GMCs tend to get fatter and shorter with age. While you can try to pull the sides in against the interior cabinet walls, the most common solution has been to bend the door to match the coach curve. Possibly a combination of both. Going back through the archives at GMCCOOP, you can probably see the process.
Those are a few of the issues unique to GMC, that an average mechanic may not be aware of. Beyond those, you are dealing with a 40 year old machine, and most of the rest of the issues will be common to other coaches.
Most of the time, the site size restriction is only for the purpose of convenience. I've had one place say that if I can get into the spot, I was welcome to it. It took some playing around, but I made it work, without overhanging my spot. I've had the person at the gate look based on size, and then go back and review based on one size smaller, just to get something available, without me even asking. Seems like most things are negotiable.