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75 blazer guzles gas

G

gm guy

1/2 ton status
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May 1, 2004
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Location
Vancouver Island but work in Ft Mcmurray Alberta C
OK, I have a 75 blazer with a 400 sbc and it runs great. My problem is I like to drive this truck allot but I can't aford the gas. I have changed motors before, so I can do this myself. Any idea's or opinions? I never realy liked the 305's but maybe a fuel injected one would be better. Should I go with a 305 or a 4.3 motor? /forums/images/graemlins/confused.gif
 
what are some of the specifics of your truck? gears, tire size, trans, case. im going to assume you're still running a Quadrajet. do not even consider the 305 or 4.3, less power produced by the engine means that the engine will have to work harder, and get worse fuel milage.
 
I would say your best bet, rather than changing motors is to swap in an overdrive tranny to get better fuel mileage.
 
Lets see, 4 wheel drive truck and crappy gas mileage ??? It's a cross we have to bear, but it's worth it in my opinion !!! Build the truck for power and forget the MPGs. For MPGs, get a cheap econobox little car. /forums/images/graemlins/whistling.gif
 
I think a 700R4 tranny would help more than anything for extended higway driving. Also a good carb tune-up. /forums/images/graemlins/thumb.gif
 
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I just want 15 mpg

[/ QUOTE ]

ah hahahahaha
/forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif
/forums/images/graemlins/histerical.gif /forums/images/graemlins/histerical.gif
snort, laugh, snort
*wipes tears from eyes*

I'd love to get 10MPG from either of my gas chugging pig blazers. Usually hovers between 5 and 8 depending on how I drive. PA mountains are hell on gas milage. I have been tempted to snag a sub $1,000 used civic that gets 30MPG for my long trips where the blazer isn't required.
 
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I see your point and I'm not expecting 30 mpg I just want 15 mpg. I don't want a pos 4 banger, but I think that tpi could make the difference I want. My 400 sbc is old and tired, thats probly half of my problem.

[/ QUOTE ] I would rebuild the 400sbc and convert it to TBI befor going to a 350. I love the torque my 400sbc has over a 350.
 
get a 4 speed or overdrive tranny, and a fresh 350, add the propper gearing, a new quadrajet and some profeshinal tuning on a dyno..walla /forums/images/graemlins/grin.gif
 
I get 16+ mpg from my Jimmy with 5" of lift and 39.5" TSL's, 4 speed and 4.56 gears. Of course the 6.2 diesel is a lot more efficient than a small block /forums/images/graemlins/grin.gif A smaller truck with a 6.2 and an overdrive can easily break 20 mpg using the 6.2.

I can easily afford to drive mine daily, so I do. /forums/images/graemlins/waytogo.gif

For comparison my old 350 was netting me 9 mpg on the freeway before. /forums/images/graemlins/yikes.gif

So you can have your cake and eat it too...

Rene
 
11-13 on the highway, about 10 or so around town depending on how heavy my foot is. /forums/images/graemlins/doah.gif
 
The feel of a fullsized truck is well worth the extra money for gas. I won't be another 4 banger S-10 driver, but I do want better milage. I think a trans swap and a rebuild on the motor should help, also 3.73's instead of the 4.10's. Any tips on a fuel injection conversion? There are a ton of fi 350's around for parts. Is the 400 intake manifold different from a 350? Again thanks for the input. /forums/images/graemlins/k5.gif
 
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Is the 400 intake manifold different from a 350?

[/ QUOTE ]

No it is not. All small block intakes will physically bolt on to each other from the begining of time ( to Chevy guys thats 1955 ) to the vortec era. When TBI and TPI came out in the 80's, the center intake bolts were angled differently, but can be made to work as the front and rear holes were the same, so its just redrilling the center ones . /forums/images/graemlins/k5.gif
 
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...also 3.73's instead of the 4.10's.

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If you're running 35's and plan on sticking with them, DO NOT swap your 4.10's out. What little gain you may get at highway speed will be wiped out (and then some) as soon as you have to accelerate from a stop (which we all know happens fairly often...) Plus, you'd be going the wrong way when it comes to offroad performance.
If you want to stick with an automatic, find a late 80's/early 90's 700R4/4L60 from a 4wd truck (I THINK '92 is the cutoff for the non-computer-controlled ones; if I'm wrong someone will point it out), get a quality rebuild done on it, and install it with a big trans cooler. This will probably net you the biggest mileage gain you'll see. Converting to FI will probably net some mileage too, but not as much as the OD trans (unless your carb is WAY out of tune). If your motor is tired, a rebuild will probably help, too.

FYI, my '87 with a tired TBI305, 700R4, 3.73's and 33" AT's gets about 14mpg on flat, open highway. As soon as hills or traffic come into play on that highway, it'll drop to about 11-12mpg. Stop-n-go urban driving is 9-10mpg.
 
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also 3.73's instead of the 4.10's

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STOP RIGHT THERE. With 35" tires you dont want to step down to 3.73 gears. It will actually hurt MPG due to the extra strain.

I get 14-15 MPG out of my '79 Chevy 3/4 ton 4x4 running stock springs, 285/75R16 tires (about 33"), 4.10 gears, a tired 350 and a 4 spd SM465.

If you want to improve the economy you might want to step down to 33" tires and stock springs (or possibly down to a 2" lift) then swap out your tranny for either a 4 spd or 700R4 (auto/OD would probably help the most for MPG). Or if you want to keep the 35" tires regear to 4.56 and swap in the 700R4. Dont make the gearing higher, it only makes your motor work harder because it wont be running in its torque peak where it is most efficient.
 
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