I used to have 2 of em..
My 81 G10 Van,and 79 C10 I have both were originally equipped with 250 straight sixes..but both of them were the less desireable "Camelhumper" versions with the 2 BBl "Vari Jet" carbs and integral intakes..my Van motor ran ok,but it was way underpowered..it took forever to hit 65 mph,and could only maintain 49 mph on hills!--it would downshift into second gear a lot,and it went slower than it did if you babied the gas pedal,and stayed in third..I later put an equally anemic 73 307 V8 in it..not that much better,but it got better mpg by 3 mpg..still a slug though,with 2.73 gears and 235/15 tires..I think the six had more torque!...
The 250 in the 79 C10 had 116,000 original miles,and ran pretty sweet the first 2 years I had it--I put an Edelbrock 600cfm carb on it with a homebrew carb adapter I made..it ran well and got 15 mpg..I disconnected the secondary barrels linkage..it didn't need them,it ran better just using the primary barrels..it had much better power and torque than the van's 250 did with the stock 2 barrel rochester ..
But one day while sitting in traffic,I heard a "snap" noise,and it started skipping..a few days later on the highway,it REALLY started making BAD noises..and smoked like crazy,and I lost at least 2 cylinders..when I got home 14 miles later,I yanked the motor out and got a 305 V8 from my friend who was junking an 86 G10 van --when I was done swapping the motor,I took the head off the 250,and #6 piston was missing a large chunk out of its top,and I could see the top ring showing!..
..it didn't scar the cylinder wall,it probably could have been rebuilt..but I used it to add weight to my other truck I was junking instead..I don't like the "Camelhumpers" with integral intakes much..kind of a POS..
I like the straight sixes..but the ones before 1973 were MUCH more durable..I think they got better mileage with the 1 BBL carb than the later 2 BBL ones,though the integral head motors did have a BIT more sack than the 1 BBL...not enough to justify the decrease in durability IMO..
I liked the 235 and 261 sixes even better..they were a lot more torqey than the 194,230,250 motors..the 292 was the best six in the later years,had the longest stroke and most torque--but were pigs on gas..nearly indestructable though..
