First long trip went well with few hiccups

radcaddy

Member
Aug 15, 2020
95
34
18
Clayton, NC
I was well pleased overall with the performance of the GMC on the first long trip in our Sequoia, from Raleigh to Harrisburg, PA and then to Oshkosh for the airshow. Came home 10 days later on a more direct route: via Indianapolis, Dayton, Charleston WV, Beckley, WV.

The total drive time was around 36 hours and maybe 2300 miles. The fuel economy ran about 8.5 - 8.8 mpg. I tried to run non-ethanol most of the way, using the Pure Gas app to locate stations, but had to fill with premium unleaded a couple of times.

Most of the way I drove State and US highways when able, and generally at 45-55 mph. At those speeds, my rig runs great and drives effortlessly. Smooth and quiet. So enjoyed a lot of small towns and cornfield-lined byways across WI, IL, IN and OH. It also ran the interstate easy at 62-70 at 2100-2200 RPMs. When the big trucks blow by, tends to move me sideways.

Going over the mountains, on the longest pulls uphill, the coolant temp climbed to around 230°, but was otherwise just perfect during all other times. It would cool off quickly and I just stopped for a bit whenever it was too hot. I experimented with dropping down into the S gear on the longest grades, which resulted in about 2900-3000 RPMs and caused more rapid coolant heating. The oil temps were fine.

I have a small seep from the right side valve cover. I think this contributed to it using about a quart of oil per 10-12 hours of drive time.

The living systems were good. The Black Tank monitor being INOP was just a minor issue. We learned that 3 days was the max between needing to dump. I simply stopped whenever the opportunity presented itself to dump and having the macerator makes it so easy. Love’s Truck Stops, some Rest Areas and the campgrounds provided plenty of opportunities to keep it empty, which also eliminated any fumes building up.

Enroute repairs were needing to re-wire the under-dash AC blower motor switch, which had stopped working. I got a new switch from Amazon and was glad to have fixed this. The old one looked charred and was hot. It was falling apart.

I also proactively replaced the carb fuel filter, so had no issues with it bogging down. I chose to do this while the engine was cold - the last time I had to do it on the side of the road with a hot-ass engine. The filter had a lot of rust particles, so I know I need to tend to dropping the tanks and cleaning/sealing them to stop the problem.

The shower and bathroom worked great, learned a good way to manage showering. I cooked one meal on the range to try out the gas burners and that was easy.

The Onan troll worked great, never failed to start up and kept us cool at every stop. We worked really hard on it, so I am very happy to have it become dependable.

So a success. I have my short list of mechanicals to improve: black tank, fuel tanks, heavier duty brake booster.

I got a lot of good experience with it in various conditions. I could pretty much live in it. Gratifying after such a long two years of working on it to feel it is reliable and useful.

By the way, we stayed at the Seaplane Base at Oshkosh. Here are a few pix:

OSH22 - 1.jpeg OSH22 - 2.jpeg OSH22 - 3.jpeg OSH22 - 4.jpeg OSH22 - 5.jpeg OSH22 - 6.jpeg
 

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Matt Colie

Well-known member
Oct 25, 2019
1,549
456
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South East Michigan near DTW
Todd,

Nice report and great Pix. We should do more reports like this so those that don't know GMCs can be reliable. Many of us could write a few more at time. But, Honestly, it would get boring for us. A few years back, we did an excursion that was 11,800 miles and in the process broke a drawer guide. (I repaired it with wood glue while on the run.) See, Boring.

A Sensitized booster is nice, but it will not get you more maximum brake service pressure. The is limited by the 14.7 of the atmosphere. If you really need more brake pressure, there are systems that can do this.

Matt
 
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tmsnyder

Well-known member
Oct 7, 2019
1,266
316
83
Buffalo NY
I was well pleased overall with the performance of the GMC on the first long trip in our Sequoia, from Raleigh to Harrisburg, PA and then to Oshkosh for the airshow. Came home 10 days later on a more direct route: via Indianapolis, Dayton, Charleston WV, Beckley, WV.

The total drive time was around 36 hours and maybe 2300 miles. The fuel economy ran about 8.5 - 8.8 mpg. I tried to run non-ethanol most of the way, using the Pure Gas app to locate stations, but had to fill with premium unleaded a couple of times.

Most of the way I drove State and US highways when able, and generally at 45-55 mph. At those speeds, my rig runs great and drives effortlessly. Smooth and quiet. So enjoyed a lot of small towns and cornfield-lined byways across WI, IL, IN and OH. It also ran the interstate easy at 62-70 at 2100-2200 RPMs. When the big trucks blow by, tends to move me sideways.

Going over the mountains, on the longest pulls uphill, the coolant temp climbed to around 230°, but was otherwise just perfect during all other times. It would cool off quickly and I just stopped for a bit whenever it was too hot. I experimented with dropping down into the S gear on the longest grades, which resulted in about 2900-3000 RPMs and caused more rapid coolant eating. The oil temps were fine.

I have a small seep from the right side valve cover. I think this contributed to it using about a quart of oil per 10-12 hours of drive time.

The living systems were good. The Black Tank monitor being INOP was just a minor issue. We learned that 3 days was the max between needing to dump. I simply stopped whenever the opportunity presented itself to dump and having the macerator makes it so easy. Love’s Truck Stops, some Rest Areas and the campgrounds provided plenty of opportunities to keep it empty, which also eliminated any fumes building up.

Enroute repairs were needing to re-wire the under-dash AC blower motor switch, which had stopped working. I got a new switch from Amazon and was glad to have fixed this. The old one looked charred and was hot. It was falling apart.

I also proactively replaced the carb fuel filter, so had no issues with it bogging down. I chose to do this while the engine was cold - the last time I had to do it on the side of the road with a hot-ass engine. The filter had a lot of rust particles, so I know I need to tend to dropping the tanks and cleaning/sealing them to stop the problem.

The shower and bathroom worked great, learned a good way to manage showering. I cooked one meal on the range to try out the gas burners and that was easy.

The Onan troll worked great, never failed to start up and kept us cool at every stop. We worked really hard on it, so I am very happy to have it become dependable.

So a success. I have my short list of mechanicals to improve: black tank, fuel tanks, heavier duty brake booster.

I got a lot of good experience with it in various conditions. I could pretty much live in it. Gratifying after such a long two years of working on it to feel it is reliable and useful.

By the way, we stayed at the Seaplane Base at Oshkosh. Here are a few pix:

Great float plane pics!

I took my dad, two brothers, his brother and friend out to OshKosh last year in a SOB. We stayed in the 24 hour generator field. It was too much for them, too hot, too far to walk for 3 80 year olds, one with heart problems. We have a fall trip up into Maine planned this year instead.

Do you have a wet-bath? Do you love it as much as I do???? It's literally my favorite thing to do while camping, there's nothing like a Navy shower imo. So refreshing and it only uses a gallon of water or so. I love it.

Unless the PO put in a bigger tank, your fresh water tank should not be able to overflow your black water tank, they are both 40 gallons. If you have a functional fresh water gauge, the black water level is just the inverse of the fresh water level. Check out the SeeLevel, I installed one and documented it in my build thread. It's great. Easy to install. Reads out to 1% .

It would be a good idea to drop your tanks and replace everything with ethanol resistant fuel lines. Rebuild the carb with ethanol resistant part, change the fuel pump, .. then you can burn E10 gas. Cheaper and more available than E0.

If you aren't completely plugging your tiny on-carb filter frequently, then you can probably just install an inline big spin on filter from TSC and not bother to boil out or line your fuel tanks, they are probably fine as is and the spin-on filter will catch any rust from the fill tube.

3000 rpm was the normal, driving down the road in 3rd gear, rpm for all automobiles of that era. That won't hurt the motor at all, it doesn't lug the motor, fluids will be circulating well and the oil pressure will be good and high. In fact, that's right where they run best and the tranny will be happiest there too if you leave it in S (2nd gear) in the hills especially .

One quart of oil burned / leaked in 500-600 miles seems fine to me. If you're leaking it, that can be fixed and the remaining amount of oil being burned would be at a perfectly normal level. The engine is doing work, it's supposed to burn a little oil doing it.

8.8mpg is what I get too, with the cheapest stuff they sell, typically 87 octane and 10% ethanol.

Great trip report!
 
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radcaddy

Member
Aug 15, 2020
95
34
18
Clayton, NC
Great float plane pics!

I took my dad, two brothers, his brother and friend out to OshKosh last year in a SOB. We stayed in the 24 hour generator field. It was too much for them, too hot, too far to walk for 3 80 year olds, one with heart problems. We have a fall trip up into Maine planned this year instead.

Do you have a wet-bath? Do you love it as much as I do???? It's literally my favorite thing to do while camping, there's nothing like a Navy shower imo. So refreshing and it only uses a gallon of water or so. I love it.

Unless the PO put in a bigger tank, your fresh water tank should not be able to overflow your black water tank, they are both 40 gallons. If you have a functional fresh water gauge, the black water level is just the inverse of the fresh water level. Check out the SeeLevel, I installed one and documented it in my build thread. It's great. Easy to install. Reads out to 1% .

It would be a good idea to drop your tanks and replace everything with ethanol resistant fuel lines. Rebuild the carb with ethanol resistant part, change the fuel pump, .. then you can burn E10 gas. Cheaper and more available than E0.

If you aren't completely plugging your tiny on-carb filter frequently, then you can probably just install an inline big spin on filter from TSC and not bother to boil out or line your fuel tanks, they are probably fine as is and the spin-on filter will catch any rust from the fill tube.

3000 rpm was the normal, driving down the road in 3rd gear, rpm for all automobiles of that era. That won't hurt the motor at all, it doesn't lug the motor, fluids will be circulating well and the oil pressure will be good and high. In fact, that's right where they run best and the tranny will be happiest there too if you leave it in S (2nd gear) in the hills especially .

One quart of oil burned / leaked in 500-600 miles seems fine to me. If you're leaking it, that can be fixed and the remaining amount of oil being burned would be at a perfectly normal level. The engine is doing work, it's supposed to burn a little oil doing it.

8.8mpg is what I get too, with the cheapest stuff they sell, typically 87 octane and 10% ethanol.

Great trip report!
Thanks for all this.