did the fuel calculations on the jimmy, its up to 18 to 20 if i keep it out of 4by and keep my foot out of it, that up from 9 to 13 mpg. quads need alot of drilling so mods are not for the faint t of heart, ill put a modified carter on for comparison, i think i have some more mileage left in the old girl.
-- Edited by 65wagon on Friday 20th of January 2017 11:18:53 PM
nothing wrong with a quad if set up right and keep your foot out of it. tiny primary and paint can lids if you open the secondaries. thats also the big jimmy, my last one a 2000 got lousy mileage no matter how i drove it 2 or 4 wheel drive.
thats why i leaned out the jets and rods on the primary sides next are the secondaries and did alot of drilling on the orfices, carters are so much easier to play with
ive been a little tardy with this one, found out this thing was a ex RC truck, explaining the 308 gears supper heavy springs and calibrated speedo, the mile and half of shorting wires under the dash along with add on AC should have been a clue too. ive done some major body, suspension redue along with the engine rebuild. 400 popped its bottom end at 52000 original miles. and to those whom noticed the snow, all this work with the exception of sandblasting the frame and undercarriage was done in the middle of winter outside including the engine build.
-- Edited by 65wagon on Friday 20th of January 2017 11:22:05 PM
Glad to see it getting fixed up....I had a 75 and it was a bit of a rust bucket and that was in 1985......They seemed to rust from day one. Thing would go anywhere though....better than my newer 4x4 in the snow
you forgot the stick welder too, if anyone was following alongwith the engine build, the mileage has settled down around a steady 14 mpg, ill have to lock out the 203 transfere case to get into the 20s with it
-- Edited by 65wagon on Saturday 21st of January 2017 11:06:15 AM
next step is unglamorous the frontend has 78000 on it now and the ball joints are done, its the winter project when I stop hauling, then the canopy comes off and its being rigged up with a 500 gallon water tank, pump and hoses for fire fighting for the spring,she going back to work.
The only K5 that could get mileage in the 20's were the diesel versions. If you can manage 15 with a '76 you have pretty much exceeded every expectation. I've had at least one K5 in my fleet without exception since 1990 when I bought my first K5, a 77 Blazer.
This was my '81 Jimmy at it's "peak".
My current K5 is a 1990 Blazer I've had since 2008. This is what she looked like when I bought it for $700.
I did some rust repair as well. My least favorite thing to do...
The passenger side was more involved, and had some collision damage at the fuel door.
On some 35's
Latest project has been to install a 5.3 LM7 and 4L60e in place of the old TBI 350 and 700R-4
I also swapped to the 4 small headlight grill which I like better.
Check out CK5.com for a boat load of K5 and square body info, build threads etc.
fr om what ive been reading its all to do with the 203 transfere case being full time, a good feature but a giant fuel waster the lockout kit should solve that problem, ive managed to squeeze 18 to 20 out of it but the 406 was not happy so we will try this, transfer case needs a update anyway, this year is starting to grow on me nice truck picks.
The fulltime AWD feature of the NP203 does eat a bit more fuel, but it's closer to 1 mpg average not 5. They're heavy trucks, with bad aerodynamics, and in '76 carb'd and no overdrive trans. That just isn't a 20 mpg combo.
that old bird only runs 1800 at 120, she only has 308 gears with 31 inch tire its just like a overdrive, granted it is a square brick but so are all these sixties cars, and as far as weight goes my 62 gmc comes in at 4100 so does my wagon and both get 25 to 27mpg. none of these run stock engines all are big cam high compression horse power motors. comparing to anything stock with all the compromises built into them really cant be done. I did notice the new fuels due reduce mileage a little but I have adapted the carb to this.
unless both tachs are out, I was running under 2000 at 80 and the speedo is accurate, this thing hits 100 and rotates the needle all the way to the stop at zero.my wagon turns about 2700 at 70 to 80 with 336 gears and 27 inch tires
Speed x rear ratio x 355 / tire diameter= rpm This is for non lock up automatics
Speed x rear ratio x 336 / tire diameter= rpm This is for manual trans and lock up convertor autos.
75 mph x 3.08 x 355 / 31 = 2645 rpm. When I initially did the math I used 336 instead, my feeling being that convertor slip would be pretty minimal at 75 mph. Which got me to this:
75 x 3.08 x 336 / 31 = 2503 rpm
70 mph x 3.36 x 336 / 27 = 2926 rpm
It's just math... The only real variable left is true tire diameter. Sidewall numbers are often optimistic. My 35's measure 33 1/4" for example.
this was the reason for two tachs, I don't trust the factory unit, I figured there must be tire swell, I know when the speedo hits the zero pin its only 4400, and it has a very tight convertor, ill have to measure the actual diameter and recheck everything but suffice it to say its a ideal cruising gear, the cam doesn't start to work until 2500 anyway.
I have often wondered how much tire flex comes into play on tire circumference at speed vs. at rest. I don't think it's too much because in the past I've measured tire circumference by marking the tire and then rolling the vehicle 1 tire rotation on nice flat ground. When I've done this and done the calculation it's always been pretty close to accurate with what the tach says.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
I have often wondered how much tire flex comes into play on tire circumference at speed vs. at rest. I don't think it's too much because in the past I've measured tire circumference by marking the tire and then rolling the vehicle 1 tire rotation on nice flat ground. When I've done this and done the calculation it's always been pretty close to accurate with what the tach says.
A e.g. 32 inch radial does not measure 16 inches from centre of rim to ground squat affects the diameter in gear ratios
wow I forgot how long ive had this truck, put 50 thousand miles on the new motor, body now has 80 total, ripped right apart to actually fix its issues, did the floor on the one side changed the body mounts for urethane, broke the flex plate center while hauling the Pontiac from Carls, broke a back cross member were its better to replace it then fix the old one , of course they ordered the truck one not the jimmy so I had to modify it, used it for work hauling heavy loads, had to fix the RCMP wiring nightmare finally
-- Edited by 65wagon on Tuesday 14th of December 2021 12:02:10 AM
