Older Chevy and GMC C/K Series (20+ years) General Discussion

cindybbcindybb Member Posts: 4
edited September 2014 in GMC
I am seriously looking at a 1986 454 GMC 1 ton dually to tow my 5th wheel. I just totalled my truck and have searched the local market and found nothing that has impressed me. I know it's 21 years old, but has only 86,000 original miles. Carb needs a little adjusting but belts/hoses are in great shape, it fires right up. Tires are new. Only one thru spot of rust on the drivers rocker panel and a few surface spots around the fender wells, one tear in the drivers seat, nothing that can't be fixed. And it will be a classic in four years. Any suggestions on what to look for that might give me problems. Hey I'm a girl and can use some manly advise on this.


  • KCRamKCRam Mt. Arlington NJMember Posts: 3,516
    Welcome aboard, Cindy :)

    Sorry to hear about your truck being totaled. While I don't tow (at the moment), I swear by my "training wheels" - been driving dually pickups exclusively for the last 11 years.

    That generation of GMC/Chevy trucks were very durable... I would have loved to have had a 1980 GMC Indy Pace Truck dually (watch "Cannonball Run" if you're not familiar with it :) ).

    Good that the truck you're looking at is a gasoline engine... whether it's the 350 or 454, lots of shops will be able to work on them - the 6.2L diesel was just not up to the task. Same with the transmission... GM automatics of that era only break if abused.

    Be sure to glance through the Chevy C/K Series: Problems & Solutions discussion. There are posts about the pre-1987 trucks in there if you look carefully, covering the Chevy and identical GMC trucks.

    kcram - Pickups Host
  • cindybbcindybb Member Posts: 4
    Thank you for the reply. Do you mean the transmission on this particular GM if an automatic may give me problems or if it was a diesel automatic? I'm a seriously thinking of replacing my 98 with the 86. Sounds like a step backward but with the cost of gas, as much as I like driving a truck everyday it's seems smarter to get a car for that and reserve this dually for my towing only. Not to mention that due to it being in such good shape it's nearly a classic.
  • jmackeyjmackey Member Posts: 4
    The price is right,but,keep in mind the 5-6 mpg as well as 6 tirs vs 4.. Add an air bag suspension for a smoother ride. I owned this year and mdl some time back. Paid 8k drove it 3 yrs & 100k miles sold it for 6800.00. Wish I had it Back !That is earlyefi as well as 4 spd auto. Add a trans cooler & keep it in 3rd unlees downhill or flat. Enjoy !
  • KCRamKCRam Mt. Arlington NJMember Posts: 3,516
    No, the transmissions of that era were actually very good, and if they do fail, it's because it was abused by the previous owner. Plus, they are easy to modify and beef up as are the engines.
  • cindybbcindybb Member Posts: 4
    I am actually getting pretty excited about this truck. Although my F150 was a georgeous truck, (black and chrome, and spit polished and beefed up to tow my 3 ton camper) The idea of a larger beefier truck with an engine that even I can work on is nice. Hell my motor home had a 454 and I changed the alternator on the road in a dress. The only thing I couldn't find that I knew was wrong was a bad ground and my mechanic finally found it. Problem is when I started driving trucks years ago, lots of the women at work and around town started driving them too. You know, the meow thing. Now they will all have to trade up to bigger ones ;).

    Will painting the whole truck (rather than just touching up the couple of bad spots) decrease its value as classic in a few years?
  • jmackeyjmackey Member Posts: 4
    The value of this truck as a "classic" is purely objective. Paint the whole truck but do not change color.if you do,make sure to jam the doors &hood,and firewall.
  • KCRamKCRam Mt. Arlington NJMember Posts: 3,516
    Painting the whole truck (and I agree with the above, keep the original color) will not only look better, it will be easier to maintain. If you just do touch-ups, you'll have all kinds of fade and mismatch problems that will never look good. Putting a professional paint job on it will ensure that you start with an even color and good finish - makes it easier to wash and wax.
  • swintersswinters Member Posts: 1
    I had a truck similar to the one you're looking at and it was great. It probably still has the HEI ignition and a Rochester carburetor and if so, recurving the distributor and changing the metering rods in the carburetor will make a big difference. The factory flyweights and springs in the distributor are a compromise because they don't know what someone will do with the truck. I changed mine (which changes the spark advance curve - hence the term recurving) to give the truck the best performance up to 65 mph. I then changed the metering rods in the carburetor, which was relatively simple, especially if you've ever rebuilt a carburetor. Both the recurve weight and spring set, and the metering rod set were for RV's and from a local NAPA dealer. I not only picked up speed on the hills when pulling my 36 foot 5th wheel but because the engine was running for how I was using it, picked up a little over 2 mpg. I later put a K&N air filter in it and that made quite a difference as well. The GM automatic should be a turbo 400 behind a 454 and it's bulletproof. The military still uses it in the HMMWV and used it in the CUCV Chevy pickups before that. It's still a favorite on the racetrack, so if that's what it has your only concern is whether it has been abused. Have a transmission shop check it out. If it's questionable have it gone through. They're not an expensive rebuild and you will be happy to have the peace of mind on the road. Heat is the killer of automatics and an external transmission cooler is a good idea too.
  • cindybbcindybb Member Posts: 4
    Your information was priceless, thank you.
  • chevy_loverchevy_lover Member Posts: 4
    I am wanting to get an engine that can switch back and forth from 4 cylinders to 8. Is there such a thing, and if so, can it be used in my 78 Chevy truck?
  • tireguytireguy Member Posts: 200
    Of course there is an engine that does this; they're called multi-displacement engines (5.3L Vortec, 5.7L Hemi). Not to sound insulting, but since you didn't know that, I'm going to assume this project is way over your head. It would involve swapping in an entire new engine and fuel management system to a truck which wasn't even fuel injected in the first place. And it's definitely not worth it to pay someone to do this on a 78 chevy pickup.
  • chevy_loverchevy_lover Member Posts: 4
  • chevy_loverchevy_lover Member Posts: 4
    I appreciate the tip. Thanks.
  • kevinodiskevinodis Member Posts: 2
  • kevinodiskevinodis Member Posts: 2
    Anyone know what my basic timing for a 350 (383) bored over with HEI ignition would be? Also my timing tab above the balancer is rusted and painted and very hard to get to, to sand down. Anyone know by description, what points are what degrees advance or retard? Thanks for the help in advance.
  • chemclchemcl Member Posts: 1
    Does anyone have a pic of how the hose that comes off the bottom of the radiator to the block goes?? The hose got taken off and we can't figure out how the new one goes back on. HELP!! A picture would be great or a really good explanation. THANKS!!!
  • infopleaseinfoplease Member Posts: 1
    Sorry to intrude was wondering if you or anyone knows were I can get info on swaping an 03 silverado 4.8 ltr into a 91 GMC 2500 series truck, or is this something that should not be attempted. I have both trucks 03 was in heavy collision drive line was not damaged although truck is beyond repair. Any info would be highly appreciated. Thanks.
  • KCRamKCRam Mt. Arlington NJMember Posts: 3,516
    I tend to recommend against putting "electronic" (especially OBD-II) engine into older vehicles simply because you also need all the electronics to come with it. All the 2003 computers, wiring, and sensors have to be there for the engine to run properly.

    kcram - Pickups Host
  • toneygoinstoneygoins Member Posts: 1
    How are the front fender emblems attached to a 1985 GMC Sierra and what is the best way to remove them w/o breaking them? Thanks
  • TapunksTapunks Member Posts: 3
    I've got a 1979 GMC 1500 Sierra Classic with massive problems. It was converted into gas because the diesel engine broke down every other week before it was a year old. 1/2 the parts are still the original diesel parts. Currently it has a 350 v8 gas engine out of a 94' Chevy van. The main problem is, the engine is soon to go. I would like to know what would be a powerful engine to replace it. I'm not worried about gas mileage, I'm just tired of going 0-60 in 16sec. or 55mph up a 5% incline. I've been told Port&polished 202 heads are good, but that says nothing for the engine.
  • TapunksTapunks Member Posts: 3
  • TapunksTapunks Member Posts: 3
    Alrighty, My trucks got massive problems. The ignition doesn't work so my father installed a switch that grounds a wire to get the starter going, and when that fails I'm forced to ground the wire directly to a bolt under the hood, and when that fails I'm forced to stick a long screwdriver down past the engine to cross the starter directly. The switch fails because it wasn't designed for the volts needed, but does work at least 2 times a day before and after work :). Now I have no idea why the ignition fails in the first place. I've recently replaced the ignition switch and cylinder, but that hasnt changed anything. My father said it's had this problem for a long time, even with a new starter, probably because 1/2 the parts are still the original diesel. I'm going to have to change the starter soon anyway. I'm having to smack it for it to work some days, and crossing the wires isn't exactly a good thing for it. Any ideas? I've currently got a 350 v8 gas engine out of a 94' chevy van, but it's about to go. Refer to "79' Sierra Classic New engine?" about what engine might be in my truck.
  • sonofasailorsonofasailor Member Posts: 2
    I everyone, I'm new to the forum and I have a question: I'm looking at a 1989 GMC 4x4, short box, V8 with 106,000 original miles (or so the owner says) on it. The body has been repainted and the interior looks good. I'm taking it for a test drive next week and I'm going to have my mechanic give it the squint eye. What should I be looking out for with this particular model? Thanks in advance!
  • sonofasailorsonofasailor Member Posts: 2
  • cumminsdieselcumminsdiesel Member Posts: 2

    If I were you, I would have bought the truck. The small things (rust, etc) can easily be fixed, and yes, it is correct - technically this truck already is a classic. I am personally considering a K5 Blazer.
  • hotrudderedbumhotrudderedbum Member Posts: 4
    The truck is a 5.7L 2WD with only 137K on it and I hope to keep it forever.

    I recently disconnected and bypassed the oil cooler hoses from the radiator while troubleshooting a curious high oil pressure indication. When I went to reconnect the hoses I found the lower fitting on the radiator stripped (the rad was replaced several years ago, too late to raise a warranty issue).

    The nut that threads into the radiator is fine.

    My question is...Is the female thread in the radiator an insert, sort of like a helicoil, or is the thread milled into the radiator body?

    I'd really prefer to not have to put in another new radiator.

    Any ideas?

  • warren73078warren73078 Member Posts: 2
    1986 Chevrolet truck, 350 engine, ¾ ton, 4 speed manual – bought the truck recently, after replacing carburetor, distributor, cap, rotor, wires, vacuum hoses, radiator, thermostat, also pulled emission controls off. I hauled a 27’ 5th wheel to the lake (80 miles), no problems and ran and pulled good, on the way back it developed a dead spot in acceleration between acceleration and de-acceleration. The exhaust smells gaseous. Checked all the vacuum hoses, connections, etc., adjusted timing. What now?

  • warren73078warren73078 Member Posts: 2
  • portola1portola1 Member Posts: 4
    I just bought this truck,it has 78,000 miles on it and I thought it was a good deal, 350 engine,auto. I have several issues:
    Heater: I can't get the heat off the floor. It won't blow on the mid range dash vents or on defrost. I have removed and taken apart all three actuators and they all seem to work. I have pulled apart as much of the dash as I can to get to the vents thinking they might be jammed or rusted shut. I am unable to get close enough to manually open them. I noticed the radio controls for speaker settings are sketchy and wondered if it isn't the push button controls for the heater system that are bad.

    4 wheel drive went out on me Christmas morning, stranding me in the sand for a couple of hours.It went into 4 high, the fell out into 2 wheel only. I have the stick on the floor shifter system, light doesn't go on. I had to be pulled out. I have read about the "shift actuator" in other posts. Maybe that's it, I don't know. I figure with the low miles and barley used 4 wheel drive by previous owner, it can't be anything big like the transfer case. I can't figure out why they don't make these actuators fail in 4x4 only so you don't get stranded in 2 wheel drive..

    Radiator leaks. I can handle that though. Kind of disappointed as I am used to old Jeep CJ's with manual hubs and go anywhere attidtude.

    Body is in great shape and it is a looker. I want to get it up to speed mechanically and drive it lightly. I appreciate any help.
  • portola1portola1 Member Posts: 4
  • portola1portola1 Member Posts: 4
    I think my power steering cooler is leaking. Anybody know how to get to it? It is attached to the radiator on the side. I can see it though the grill. Maybe I have to remove the grill to get at it?

  • sparkles2sparkles2 Member Posts: 1
    just had new shocks put on drove it about 100 miles.went to go out started when i put it in gear .manual it sounded like metel 2 metal screaming it does it sometimes when i try changing gears.can someone help me PLEASE? sparkles2
  • cowboyfromhellcowboyfromhell Member Posts: 1
    Just bought 1975 K20, 350eng, Holley Carb and others, it starts right up, idles great, put it in drive or reverse no problems... press on the accelerator and it wants to die, for 1 i was told the Holley carb is probably in need of some adjusting, but they can be a pain in the neck, and frankly i have no idea what i'm doing, haven't checked the timing yet but that'll be next, please someone give me some tips, i'm an automotive idiot
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