7 MPG!!!! Yikes!!!

[NORMSCOLORADO]

in the past couple of days drivin the green machine..... i figured out the mileage and its around 7..... so anyway i wanna get rid of my 5.14's and get a rearend a little higher geared.... what is the best way to go about this? i have a buddy that gave me a rearend (4.10's) and cast iron 4 speed out of a 84 c20.... the truck had a 6.2 that we put in another truck i am unsure about it fitting in the 67... i im pretty sure the bell housings will interchange but dunno....

[Shyguy]

It all depends on your engine, transmission, rear gears and tire size what mpg you will get.

I had a 350 in my '71 with the old type 4 speed, 3.73 rear gears and 31's on the back, with that setup I was getting 12-14 mpg depending on how I drove.

I am not sure what I will get now with the 454 and the same setup.

I use to have a '72 GMC with a 350, old style 4 speed and 4.1? in the rear with stock tires and normally got about 10 mpg.

I am sure others will chime in with more information.

Danny

[NORMSCOLORADO]

duh i should have metnioned that! lol im running the factory 327/ sm420 (7:1 1st gear granny take off in third ) 4 speed.... with the 5.14's in the back and im runnin 265-75x16 at 45mph im crankin about 2600 rpm

[67_C-30]

Originally Posted by NORMSCOLORADO

in the past couple of days drivin the green machine..... i figured out the mileage and its around 7..... so anyway i wanna get rid of my 5.14's and get a rearend a little higher geared.... what is the best way to go about this? i have a buddy that gave me a rearend (4.10's) and cast iron 4 speed out of a 84 c20.... the truck had a 6.2 that we put in another truck i am unsure about it fitting in the 67... i im pretty sure the bell housings will interchange but dunno....

6.2's fit quite nicely in '67 C-30's if you get big block motor mounts! They'll also get 18-20 mpg in a truck as light as these are.

[capev86]

i have gotten 10-11mpg with mixed driving in my 72 burb 3/4 ton 2wd 307 3onthetree 4.57 gear. i have a 4.10 third member ready to go in the axle and that should get me in the 12-14mpg range, especially in highway driving. i don't go over 55 for long distances 'cause the engine screams with such speed gearing. also planning to add the factory borg warner OD unit to the trans and that should get me in the 16-18mpg range if i keep to 60mph.

[292farmer]

sorry for hacking post, what is the borg OD unit, and does it fit only on certain trannys or pretty universal? thanks and sorry again

[big mike71]

I only get about 7 1/2 or 8.

[NORMSCOLORADO]

Originally Posted by 67_C-30

6.2's fit quite nicely in '67 C-30's if you get big block motor mounts! They'll also get 18-20 mpg in a truck as light as these are.

i want to go that route so bad but i am gonna wait till the 327 goes which if this trans and rear works ill be all set..... does anyone know if it will fit?

[capev86]

if i had tons of money a 6.5 with banks kit and a mechanical clutch 6 speed (with .7 5th and .52 6th gear) and a 4.10 rear end would be awesome in my 72 burb 3/4 ton. soo much torque and the fact that they are not high revving and you can go insane with the overdrive ratios!

[67_C-30]

Originally Posted by NORMSCOLORADO

i want to go that route so bad but i am gonna wait till the 327 goes which if this trans and rear works ill be all set..... does anyone know if it will fit?

Yes, they fit pretty easily. I put one in my '67 C-30. You have use big block engine towers, but its pretty much a bolt in deal. The 6.2/6.5 will bolt to any Chevy transmission, and the mechanical injection pump engines '82 - '93 are very simple to wire up (no computer). I turbocharged my 6.2 with 6.5TD stuff, and that requires you to run the exhaust out the passenger frame rail, but that's no big deal. I just got my running this past weekend, and I'm going to try have the front clip back in a week or two. I'm adding hydroboost brakes/power and power steering before I put it back on. Here's a clip of the big green beast!

YouTube- IT LIVES! 6.2L Turbo Diesel in '67 C-30...

[67_C-30]

Originally Posted by capev86

if i had tons of money a 6.5 with banks kit and a mechanical clutch 6 speed (with .7 5th and .52 6th gear) and a 4.10 rear end would be awesome in my 72 burb 3/4 ton. soo much torque and the fact that they are not high revving and you can go insane with the overdrive ratios!

I'd love to have a 6 speed for mine, and hopefully one day I can. I did go with the close ratio NP435 instead the SM420 or SM465 that is more common in these trucks. It really isn't a granny transmission like the SM420 and SM465. It has 4.56 first gear as opposed to the 7.05 : 1 and 6.55 : 1 of those 2. You actually use first gear with close ratio NP435, and I'm going with a higher rearend ratio to get a decent highway gear.

[CE20934]

With the 400, I would get 12-14 in my truck. With the 427, I get 7-8. Same trans & rear end (SM420 & 4.10) though.

I can hear my wallet being sucked through that Qjet.

[kevmic28]

I have a 70 with a 350 bored 60 over with a 350 tranny. I calculated my last trip pulling a pop up trailer and my Harley and camping and fishing gear for a week on the beach in the bed at just over 14 MPH. Im guessing its driving style with it loaded cause I dont get that good when its not loaded down.

[gonzo6869]

FYI to all. A common misconception, is that the weight of what your hauling or towing will affect your mileage. The truth is, If your on the freeway, on a long distance drive, it will not affect your MPG. Now as far as stop and go traffic or city driving, that is where you'll see the difference.

[Beelzeburb]

I used to get a consistent 7.5 mpg around town and 10 mpg highway in my K10 Suburban when it had a q-jet 355 / 700R4 / 3.07 gear ratio and 31" tire setup. I'm hoping for 11-12 with the TBI 454 / 4L80E / 4.11 ratio and 35" tires.
If I was interested in fuel mileage I'd drive something else.

[67_C-30]

Originally Posted by gonzo6869

FYI to all. A common misconception, is that the weight of what your hauling or towing will affect your mileage. The truth is, If your on the freeway, on a long distance drive, it will not affect your MPG. Now as far as stop and go traffic or city driving, that is where you'll see the difference.

I'm sorry, but I totally disagree with that. You can put a 1000 pounds in the box of a pickup without nothing sticking up to change the areodynamics, and you will lose MPG on the highway. Not as much as in the city, but it will affect it. When towing something, the aerodynamics play into as well the weight. I've towed cars/trucks, 4 wheelers, engines/transmissions, campers and just about everything else and this has been aleways been my experience. You can't expect when an engine that is moving (X) amount of weight at (X) amount of speed to not change when you change the amount of weight with all things being equal.

[capev86]

sounds like someone slept through their physics 1 class! if you take the drag racer (crude) formula for determining power to weight, etc....100 pounds = 10 horse power. you start to see why you need to expend more weight you are moving, the more energy is used to move it. unless you are in a vaccum, it takes some energy to maintain that speed also. then you add in air and tire friction.....

my dad can get 18mpg out of his 87 burb 1/2 ton 2wd iwith 350, OD and 3.73 rear. he gets like 8-10mpg when he is hauling the family camper.....a '71 holiday trav'ler 23 footer that weighs 6,000 pounds loaded.

[Pickupmanx2]

67_C30,,,,AWESOME!!! I get about 7 or 8 in my pig,, 400BB400trans, not sure of the rear ratio yet, I heard they came with 3.08 behind all BB,,,,I 'll have to pull the cover some day here and count.

[C-10 simplex]

Originally Posted by 67_C-30

6.2's fit quite nicely in '67 C-30's if you get big block motor mounts! They'll also get 18-20 mpg in a truck as light as these are.

One question i had about the 6.2 was that the fuel pump appears to be a stock type identical to the gas sbc/bbc? i thought diesels need hi-pressure fuel pumps?

[nicks05z71]

thats a lift pump. that pump supplies the injection pump. in that video of the 6.2 running, he is manualy operaterating the throttle on the injection pump.

[67_C-30]

Originally Posted by C-10 simplex

One question i had about the 6.2 was that the fuel pump appears to be a stock type identical to the gas sbc/bbc? i thought diesels need hi-pressure fuel pumps?

Originally Posted by nicks05z71

thats a lift pump. that pump supplies the injection pump. in that vedio of the 6.2 running, he is manualy operaterating the throttle on the injection pump.

nicks05z71 is correct, its the injection pump that makes the crazy high pressure. It takes 1300 psi to pop the injectors stock, and the ones I'm running at 1800 psi marine injectors. The lift pump only has 4 - 6 psi. It really is the same as regular GM pump, except it has a longer arm.

[67_C-30]

Originally Posted by Pickupmanx2

67_C30,,,,AWESOME!!! I get about 7 or 8 in my pig,, 400BB400trans, not sure of the rear ratio yet, I heard they came with 3.08 behind all BB,,,,I 'll have to pull the cover some day here and count.

Thanks! I got the throttle hooked up today, drove it around a little. It is really torquey! The turbo whine is much louder under a load and it starts from the second you give it any throttle. You couldn't slap the smile off my face when I was driving it around today!

[Pickupmanx2]

Originally Posted by 67_C-30

Thanks! I got the throttle hooked up today, drove it around a little. It is really torquey! The turbo whine is much louder under a load and it starts from the second you give it any throttle. You couldn't slap the smile off my face when I was driving it around today!

I have 2 7.3s both straight-piped,,, I LOVE it, the turbo whistle is sweet, sweet music! Drove a tow-truck years ago with the 6.5, great engine.