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Swapping rear gears would help alot no doubt. 3.08s and 32s definitely is not helping the motor any. My blazer has 3.73s and 33s and that's about the highest I'd go for 33s
There’s no lugging with 4.10s. If it’s driven on the highway, 35s and 4.10s is still wound like a clock. Highway rig, more like 3.42s and no or on 35s would be much better.
Truck has a lift already that I would like to keep so smaller tires aren't really an option, smallest 33s but they even look a bit silly on it at the moment. With 3.42s I'd be 400 rpm lower on the highway but I feel like I'd be sacrificing a lot of pickup around town with big tires and that gearing.
It's possible... occasionally, but not probably. 15-20 is pretty normal for a fuel injected 1/2-ton blazer/tahoe/suburban if you are in an area where freeway driving stays below 70mph.
This kind of thing is pretty regularly said on GMT400 forums too, then once people start asking questions and picking it apart it comes to light that it is more like 15-20mpg and that is questionable because it is not running factory tire size and the speedometer has never been calibrated.
That all makes sense. My whole thing is there is a certain sweet spot of power and efficiency especially in a heavy vehicle. You can have an underpowered stock motor that gets far worse mpg than a modified motor because the motor needs to worked much harder, hence why a lot of times rv cams increase power and mpg. I'm trying to achieve around that point, hence my cam choice and lockup converter and what not, since the truck no doubt will have modern power. More power also means less throttle needed to get to speed with a quadrajet, less secondary usage compared to a stock underpowered motor getting to speed, causing more efficient power because as we all know once the secondaries open the gas needle drops. I'm just shocked with how bad everyone's mpg is considering my tbi gets good mileage in the blazer that is also very heavy. I know guys with gmt 400s that also get pretty damn good mileage.
There is a set amount of torque required to keep the vehicle at a constant speed. HP is the amount of torque being applied over a distance(RPM). HP means nothing in this case. There is a curve in the engine where BSFC(Brake specific fuel consumption) is best, this means that there is an RPM and throttle position at which the engine produces the most power with the least amount of fuel. For max efficiency, you want the engine to be in that band when cruising. RV cams generally increase fuel economy and torque under the curve because they are focused on maximum efficiency at low RPM's where the engine spends most of its life around town and when towing.
Drivetrain will definitely be more loss, but the weight will probably be the same, Blazer weighed in at 5700 lbs at the metal yard with me and some tools in it, according to the NY dmv my crew cab (which is the absolute basemodel not even a radio from factory, while the blazer is a silverado) weighs 5300, which sounds about right my buddy has a crew cab 8 foot bed diesel Ford from the 90s and that I believe it weighed in at just under 6000, and it isn't a base model. Your right about the aerodynamics, these trucks are all bricks. As for mpg claims I think a lot of it is people choose not to want to believe them. Obviously 12v guys saying their dodge gets 30+mpg is bs and outlandish stories like that but for example my blazer gets 20 easy highway. Factory was rated 17 highway, now mess with gearing, change for a much less restrictive exhaust, slight performance upgrades, and even small things like more efficient synthetic oil, it's not hard to add on a couple to a few mpg. Obviously the biggest difference would be pedal control. I'll check out that link.
TBI has swirl port heads,they get better milage,that was the point of them. Everyone hates The 193 heads,but they sure get better milage. That and better feel control,timing control and EGR it all adds up
People choose not to believe it because it isn't true. You don't get better MPG with all of that added, in fact you usually get worst MPG. You might CALCULATE a higher MPG because you didn't account for how wrong your odometer is now that you changed your gear ratio and tire size though. I can believe 20mpg for a very well designed and tuned SBC in a blazer sized vehicle. But that would need to be absolute best mileage seen and with an OD equipped vehicle on mostly flat ground at slower highway speed. 17MPG highway is pretty much what those get for real life highway mileage.
