1975 GMC 6500 dump truck with 366ci gas big block

Dargo · Dec 2, 2010

Anybody on here ever have one of these? I don't really need a dump truck right now, but this is a one owner a family friend owns and has never sat outside overnight and I can't find any rust anywhere on the truck. He had the bed removed, media blasted and painted with some hard enamel paint about every 5 years. It has average tires, new brake booster and wheel cylinders, original interior that doesn't even have a rip in the seat and has 29,XXX miles on it.

I really don't know anything about the old 366 truck engines (he says it's a big block), but it started right away after sitting for weeks, didn't smoke and idled just fine. I wouldn't even consider this thing except it's darn near in perfect condition and I think I can get it for a reasonable price.

My questions are; is that a decent truck? It's bed looks good and is a 6 yard bed and the engine, transmission and brakes are good. My next question is what really would be a "reasonable" price for something that old?? I can't really go out of a book, because it looks better than some 2009 trucks I've seen. Any thoughts or comments on that old truck? My use would really be moving dirt on my property and saving time and wear on my tractor moving dirt 1 yard at a time.

tcartwri · Dec 2, 2010

The 366 is a small bore tall deck Big Block. Pretty tough motors. They love fuel though.

Diamondpilot · Dec 2, 2010

I have been running a 1978 Chevy C60 with a 6 yard bed, 4 speed, and a 350 2 barrel. Its a pig but gets the job done. If it did not have the high low rear end it would not move on its own from a dead stop. Its a good solid old truck that does everything we have asked of it but sure is slow. About 45 mph wide open.

He gave $1800 for it.

The same guy has a 1976 Ford F700 with a 8 yard Marion Bed, 5 speed, and a 391 truck engine with a 4 barrel. Its much more truck but the brakes are touchy and it does not look nearly as good. It will run about 55 mph.

He has $2200 in it.

He also had a 1971? GMC C40 with a 6 yard Marion Bed and a strait 6. It was about as good as the 350 powered truck and looked good but he sold it for the Ford. 45 mph was all it would do and 6 tons or less if you planned on stopping it in the same state.

He got $1650 for it.

I am not familiar with the 366 motor. I would go to google and look around to see what you can find out. The main issue with some of these truck motors is they are expensive if you need a rebuild or even just parts.

I would offer $2250 and see what happens.

Dargo · Dec 2, 2010

Diamondpilot said:
I would offer $2250 and see what happens.

I think I may possibly get it for less than that; possibly. I'm aware that it will suck on gas, but I expect that and it won't be used on the road much at all. It's almost a shame, because it is in such remarkable condition.

I'm waiting for insurance quotes, liability only, and to see if anyone has any real knowledge of these trucks before I go back. I've seen ones in far, far worse condition with 3X the miles go for $3500. There again, there is a sucker born every day.

Dargo · Dec 2, 2010

K7LN said:
It is a big block, part of the 396, 427 family. The 366 was only used in the medium duty trucks. I can't say anything on prices since they vary all over the place. Around here, you see a lot of grain trucks that they can't give away. The only negatives I would have:

1) If you ever want to put it on the road, insurance and plates can be expensive.

2) Various seals going bad from age; wheel cylinders, master cylinder, steering.

3) Tires, if you have 9.00x20 or 10.00x20, you probably have multi piece rims that many places will not touch.

Thanks, I looked at another last week that had a 427 in it. However, it smoked like crazy, had over 200k miles on it and no brakes with bald tires. I don't want to restore one. Besides, he got $2500 for it. I was not even remotely a buyer at that price.

DanD78 · Dec 2, 2010

I have ran several trucks with that engine and all did very well. Two had 12' snow plows. I would take the 366 over a 350 in that class truck any day. The 350 lacks the lugging torque of the 366.

Dan

Diamondpilot · Dec 2, 2010

I am sure you know this Dargo since you are a been there done that guy but these trucks can get real expensive real quick. Brakes are the biggy. I have seen guys dump $2000 alone on that one item. Tires, springs, ect can also get pricey. Most everything else is dead simple and any shade tree mechanic can patch them together to keep them running.

Chris

crazyal · Dec 2, 2010

I'm assuming it's hydraulic brakes since you said booster and cylinders. IMO air brakes are easier to work, cheaper to repair, and stop better. Not sure how GM does it but my international has a master that feeds a second master with a booster mounted under the drivers door. From what I read the two things to look out for is the diaphram in the booster leaking and the seals in the cylinders leaking. Probably why they were replaced.

I would be ready to rebuild that carb as it may not like Ethanol gas. Some other things to look at would be the leaf springs, they can get rusty and swell. It's not that you can't change them yourself but they are heavy. Also look at the grease fittings, do they look like they were used? Also take a look at the steering linkage, sometimes they are costly. For around the house some slop isn't a problem but driving on the road with a load you'll want to fix it.

My international's hydraulic pump leaked where the shafts come out of it. It's a pretty easy and cheap fix but you need to go to a hydraulic shop to get the correct seals. Over all because of it's age rubber parts are probably going to br dried out and can fail.

I would expect between 2 to 6 mpg driving it on the road. but if you need some gravel around the house having your wn truck is invaluable. I could never live without mine as I'm always landscaping or filling spots. If it's in good shape I would buy it.

RickB · Dec 2, 2010

Hydraulic brakes would be a dealbreaker for me; they are absolutely cost prohibitive to repair. Price a brake job, it will make a couple years' insurance look cheap. 366's had a good reputation around here, for a gasser.