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striaght six DD duty, reliable

79bonanza

79bonanza

1/2 ton status
Joined
Mar 31, 2010
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Location
Georgetown, Kentucky
well im getting ready to but a 78 k10 inline six 4 speed 4x4, ive heard they are pretty stout motors and are very dependable but do you think they would be up to the challenge of a everyday driver. like 60 miles aday and about a 400 mile round trip every once in awhile. most are highway speeds (65 mph) tops mostly. you guys have any ideas on if it would be up for the challenge with a couple bolt on upgrades you know fuel spark air that kinda stuff. thanks for your thoughts guys
 
They were up to the task for years and years and years, not much has changed. They will still be up to the task.

I don't know much about those motors but if its points I would change that (shouldn't be if its a 78).

Thats really about all I would do just make sure everything is in good shape, the further away you get from stock the less reliable something becomes.
 
The engines are good BUT if it has the integrated head the heads ALWAYS crack. Not to worry though, if it does have the integrated head you can swap it over but you will have to swap everything that goes along with it. If you don't know what the integrated head is it is a head that has the intake manifold all cast as one with the head and the exhaust manifold bolts up from underneath the intake portion of the head. Other than that they are great engines and will give many years of use.
 
I had an '81 SWB K10 once and it had the 250 inline with a 465/208, 10 and 12 bolts with 3.73's riding on 31's in the beginning and then later 33's.

This was one of the best and most amazing trucks I've ever owned. It got me 18 mpg on the highways. I used to drive it 80 miles round trip each day back when I worked out of town, 5 days a week. 55 on a highway and then the last 5 miles on the interstate at 70.

That motor never let me down. I used to take it off roading at the same time it was my DD. I tried so hard to blow up that motor so I'd have an excuse to go with a V-8. Never happened. That motor was so reliable, I would leave the truck running for hours during the winter while I was in visiting a friend at a shop several nights. It never overheated at all.

Sure it may have been a little under powered but the economy and reliability of it made it worthwhile to own and drive. Being that the truck was a SWB, it was much lighter in weight and therefore the 250 could move it just fine. I never did anything major to the motor except for the normal oil changes, etc.

God! I miss that truck! I'd love to find another SWB and build another 250 for it but with TBI on it to see if I could push the mpg into the 20's. That'd be the ultimate dream to have a pre-'88 truck of the old body style to get over 20 mpg.
 
thatK30guy said:
I had an '81 SWB K10 once and it had the 250 inline with a 465/208, 10 and 12 bolts with 3.73's riding on 31's in the beginning and then later 33's.

This was one of the best and most amazing trucks I've ever owned. It got me 18 mpg on the highways. I used to drive it 80 miles round trip each day back when I worked out of town, 5 days a week. 55 on a highway and then the last 5 miles on the interstate at 70.

That motor never let me down. I used to take it off roading at the same time it was my DD. I tried so hard to blow up that motor so I'd have an excuse to go with a V-8. Never happened. That motor was so reliable, I would leave the truck running for hours during the winter while I was in visiting a friend at a shop several nights. It never overheated at all.

Sure it may have been a little under powered but the economy and reliability of it made it worthwhile to own and drive. Being that the truck was a SWB, it was much lighter in weight and therefore the 250 could move it just fine. I never did anything major to the motor except for the normal oil changes, etc.

God! I miss that truck! I'd love to find another SWB and build another 250 for it but with TBI on it to see if I could push the mpg into the 20's. That'd be the ultimate dream to have a pre-'88 truck of the old body style to get over 20 mpg.
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I'd LOVE to have a truck with a 292 and a 465 in it....torque monster!
 
My old play truck had a 25o six, sm465, np208, 3.73's and was running 36's on it. Could spin them on pavement even with the rearend welded. Should have never sold it. Thing was a beast
 
I"ve owned several GM trucks with staight sixes--I think my favorite was my '56 Chevy 3100 series 1/2 ton (2wd) that had either a 235 or 261 straight six..very torquey engine!..had only a 3 on the tree,but it was a strong runner,everyone who rode in that truck thought it had a 283 till I opened the hood!..you could lug that motor down to 10 mph in third and just step on the gas,and it would pull right up with no bucking or spark knocking,and the low rumble from the exhaust sounded like a big diesel...

The other straight sixes GM had were great engines--they had 194,215,230,250,and 292's,all of them had excellent reputations for durability and reliability..with a 7 main bearing crank the bottom ends rarely gave trouble..I had a 215 in one truck a friend gave me from his '64 Tempest when he decided to hot-rod it with a 400 Pontiac engine..that little engine might not have been a powerhouse,but it got 16-20 mpg often on long trips in a 2wd 71 C-10...the powerglide tranny made it sluggish though..

I had two of the "Camelhumper" integrated head 250 sixes too,one was in my 81 G-10 van,which I drove to Nashville in '92 when it had "only" 137K on it!..it was a bit slow going thru the Poconos,but it made the trip and back OK,I held that thing wide open the whole trip too,it would top out at about 80-85 mph,and bog down to 53 mph up the hills..but I never feared it failing..I eventually wanted more power ,and swapped in a '73 307 from a Malibu,and it was LESS powerful than the six,it only had 115 HP that year,VS 130 for the 250 six..I wished I had just left it alone!..:doah:

My '79 Bonanza C-10 had an integral head 250 too,with only 110K on it when I got it,it ran sweet..but I hated that Rochester 2 BBL "Vari-Jet" carb (Very-JUNK) so much I went thru the agony of making an adapter to bolt on an Edelbrock 500 cfm 4 bbl..it didn't run good with that large a carb,till I discovered I could take the secondary linkage off it and just run it on the primary barrels...unfortunately the engine lost the top ring lands on the #6 piston,probably from the spark knock it always suffered from with the stock carb..I put a 305 in it after it blew,but I missed the six,I would have replaced it with one IF I could FIND one here,but every junkyard I tried said they crushed all the old trucks and they "rarely keep a six,no one wants one"..(I did!)..

A friend used to have a 1982 C-10 that he bought at auction from the local phone company--had a 250 six with the integral head,and a FIVE speed manual!...it got over 20 mpg on trips to Maine he took it on..he eventually replaced that engine with a 250 from an older Nova with a 1 bbl carb,but it soon needed valve work,so he decided to buy a 267 V8 cheap to "upgrade" the truck,along with an automatic tranny,as his left leg had trouble "clutching" after an injury..but he didn't like the truck as much after the six was replaced,and he ended up selling it..

Just this morning on CL I saw a 1977 K-20 listed for 1500 bucks--has a 292 six (the best GM ever made IMO),and an SM465 with 4.10's --ad says its got "plenty of rust" and some holes in the floor,etc,as usual for a truck of that age here--has a working Fisher plow on it too...that would be the type of plow truck I'd like to find,only in better condition body wise...

I would not be scared to take a truck with a straight six on a ong trip--in fact,I'd prefer one over ALL my vehicles in a way--I feel much more confident driving something I KNOW I can fix myself,and do it right on the roadside if need be--hell,with most cars built after 1987,you need a LIFT and multiple tools just to change a belt or hose on one..you face a tow charge and lose the use of your vehicle for a day at the least..I'd rather be in a 60's GM truck with a straight six than say,my '95 Contour,if I had a hose or belt fail on the road!..at least I could FIX the truck!..
 
I have the original 230 in my 64 C10...still runs great...I had planned to put a 350 in it one day, but I haven't done it because the 6 runs so good...I'm thinking of keeping the 6 and rebuilding it one day...I think there is a coolness factor to keeping the 6 in it...I even like the sound of it...with the high torque of the 6 and 4.11 gears, it has plenty of low end go, but doesn't run much over 65-70, but who really needs a 1964 C10 stepside to go faster than 70mph?
 
man it sounds like the striaght six trucks are the ones that got away from everyone and now they want them back. im pretty excited now that you guys have so much good to say about them. i guess i wont have to worry to much about having a DD out of this old 78. well heck now i cant wait until i get it haha
 
My 81 K5 had the straight six in it, and like thatk30guy, I TRIED to kill it so I could swap a V8, it ran good, even burning oil at the rate of a quart every 100 miles, clattering like mad and having to stick a screwdriver down the carb to keep the choke open, it never failed. Finally got tired and swapped a V8 anyway and have been dissapointed ever since. GM made a dang fine motor with that one. When I did the swap, I pulled the pan and along with sludge, there were sizeable shavings in the black black oil. The cranks had a 1/4in end play and all of the connecting rods wiggled on the crank, yet still it ran. If I do another K5, it's going to be an FI 292 with an NV4500.
 
79bonanza said:
man it sounds like the striaght six trucks are the ones that got away from everyone and now they want them back. im pretty excited now that you guys have so much good to say about them. i guess i wont have to worry to much about having a DD out of this old 78. well heck now i cant wait until i get it haha
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Its threads like this that make me start dreaming again about owning another 250 in a SWB. :doah:

My DD now is a '98 Jimmy and even though its got the 4.3 Vortec, its very lousy on mileage in the town. I check mileage at every fillup and yesterday it came out to just under 12 mpg with mostly city driving. Not good or impressive for something this little. Hell, I could beat that if I had my old '81 back again. Hence the reason to think about finding another rust/dent free SWB K10 to build a new 250 for it but modify it a little bit with some Clifford Performance parts and a TBI.
 
I know some came from the factory with them as I watched an old '88 or '89 R-series 12' flatbed truck sell at a local auction here in town and it had the I-6 with TBI on it. Was even a 4 speed truck, too. 1 ton with narrow 14FF and 4.56 gears.

Thing sold for more than I wanted to pay for it especially when I only wanted the motor.
 
yea everything i want to buy always sells for way more than its worth lol

have any of you guys ever boosted a striaght 6 like put a turbo on one, just sounds like it would hold alot of boost i think
 
My dad had a 250 straight 6 in our '76 Nova, that thing was crazy with fuel mileage, and emissions testings too, one year they ran it through twice cause it read so low on the Co2, they thought something was wrong, if i remember right, it read a .01 on the Co2.

Finally something happened to the #1 cylinder, lost compression, he didn't have the money to fix it, so he continued to drive on 5 cylinders for the next year and a half, even ran it through emissions testing like that, and still passed, obviously alittle higher reading, but still within spec.

I remember it didn't have much power to run up a steep hill with a car full of people, but it got great mileage with the one barrell carb.

With todays fuel prices, i wouldn't mind having one again, as mentioned before, the other 1/2 ton truck we have has that 4.3 ltr in it, and it really only gets the better mileage out on the highway, around town, it's not too impressive.
 
wow...i never knew they made fuelie 292s. i drove a 292 C30 for over 10 years when i wasn't in the White. i loved that motor for what it could do and i'd surely like to get my hands on one for my next all around work truck, even another 2wd.
 
79bonanza said:
yea everything i want to buy always sells for way more than its worth lol

have any of you guys ever boosted a striaght 6 like put a turbo on one, just sounds like it would hold alot of boost i think
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Clifford Research
their 6 = 8 equipment is great; 3 into 1 headers, 4 barrel intakes, etc make big power gains in in line 6 motors I ran the dual exhaust headers with two turbo mufflers and an offy intake with a thermo quad carb and it sounded super, got great mpg, and pulled a 20 foot center consul boat (pretty heavy) like a small block would. Or you can go big budget turbos etc if money is not an issue cause they can definitely handle it.:woot:
Bailey
 
4xcrazy said:
My dad had a 250 straight 6 in our '76 Nova, that thing was crazy with fuel mileage, and emissions testings too, one year they ran it through twice cause it read so low on the Co2, they thought something was wrong, if i remember right, it read a .01 on the Co2.

Finally something happened to the #1 cylinder, lost compression, he didn't have the money to fix it, so he continued to drive on 5 cylinders for the next year and a half, even ran it through emissions testing like that, and still passed, obviously alittle higher reading, but still within spec.

I remember it didn't have much power to run up a steep hill with a car full of people, but it got great mileage with the one barrell carb.

With todays fuel prices, i wouldn't mind having one again, as mentioned before, the other 1/2 ton truck we have has that 4.3 ltr in it, and it really only gets the better mileage out on the highway, around town, it's not too impressive.
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That 4.3 needs a lot of advance. I had a 92 or 3 sport side with a 5 speed and it got about 17-18 at most tuned up but i bumped the timing 5 or 6 degrees over what was called for and it got 24 from then on.
 
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