So im still working out in my mind the relationships between parts of the engine, IE cam, lifters, pistons, etc.

What my goal is:
Build a 460 that gets decent gas mileage (approx 15mpg)
Donor Engine:
1994 EFI 460

Now, to me, it would seem that if I just built a powerful 460 that then I would get better gas mileage just on the premise that more powerful engine would use fuel more effeciently and that moves the truck easier.

However something tells me this is not the case. Would it be as simple as building something like a 400hp 460 to get better gas mileage?

I know someone will say the realized savings will be none with this project, but it's for fun too

RPM band for this engine would be idle to about 4k. So lots of low end grunt, off the line power, with power all the way through normal operating range(which 4k exceeds by about 1krpm).

So basicaly im just looking for more info, ive read many many threads, but just need this cleared up. I'm new to engine building, but theres a engine block sitting in the garage that is doing nothing.

Im not into the parts phase (writing up exactly what I need) but how does this relationship work out, what are the differences between power and efficiency?

If there are threads out there that I have missed that are obvious, I apologize, point me to em'!

-myers

 

I'd keep the compression around 9.5:1. Then, I'd run a small camshaft for EFI applications, like Comp's XE256H-14. This will reduce overlap and improve efficiency.

Basically, you're trying to maximize your dynamic compression ratio for the octane of fuel you'll be running, and minimize your RPM's. The latter is especially true for a motor like a 460. I'd run an extra low gear ratio and an overdrive. In addition, an extra low stall torque converter would probably be helpful.

In terms of the motor, you want to keep the velocity up. This means no big valves, no monster intake, no headers with huge primary tubes. This means a stock intake manifold, only cleanup on the ports to improve velocity (no "hogging out" the ports), and small primary tube headers. These would be headers with primary tubes the same size or smaller than the exhaust valve.

Basically, you're building a low end stump puller. Mileage will follow. Horsepower is the amount of work the engine is able to do in a given amount of time. To make more HP, requires more fuel. Usually, more HP = less efficiency. Torque is the twisting force of the crank at a given RPM. An engine capable of making more twisting force, at a relatively low RPM, should be capable of better mileage.

 

Lower your rear gears and get the RPM's down. An overdrive tranny would help.

 

Is getting 15 mpg out of a 460 unrealistic? These things get 10mpg stock in most configurations, that's a 50% increase in mileage.

 

Right now the vehicle is the one in my sig, I have 4.10's and will keep them for towing and what not. I know that is one way to lower mpg, but thats a sacrifice im willing to make. Additionaly the tranny I have is an E4OD, which the overdrive isn't as big as i'd like, or how would I term that? Right now my RPM in OD at about 64mph is 2k. I realize the easiest way would be to put in like 3.55's

How hard/complicated is it to install an extra low stall torque converter?

So my understanding of preformance was a little mis-aligned? a high hp engine doesn't use the fuel more efficiently, it just crams more air and fuel and squishes it harder before detonation?

I think that 15mpg highway is definetly achievable for a 460 even naturaly aspirated, it just isn't very likely for my application. Anytime you have a 8,000lbs truck.. your not gonna get great gas mileage. HOWEVER, right now im averaging 6mpg around town and about 9mpg on the highway. To me thats unacceptable for a stock, recently rebuilt 460, regardless of how big the truck is. Additionaly there are many guys ive talked to (mainly with older 460's) that get 12+mpg.

Other questions related, would using preformance distributor/ignition/wires+plugs help up mpg? Im thinking that the answer might be yes, by maybe 1mpg, at the cost of (random calculation in head) $800-$1000.

thanks so much for the help. -myers

 

I can get 14 mpg out of my EFI 460 in my motorhome as long as I drive gently, without towing, so I'd say 15 mpg in a normal vehicle should be easy.

Mine is completely stock, too.

 

i would keep the efi set up go with a good set of headers and good open mufflers like a flow master or something comparible aftermarket air intake you could even go with a stock cam 4;10's with a auto or even a 5speed a msd 5 box is cheap and will burn the fuel alot better a good set of plugs wires and dis i think will get you 15+ and have good tourq and even light up the tires for kicks

 

Ok tell me about this motorhome you are geting 14 mpg in. class / weight make?

 

It's a '91 E350 chassis, class B motorhome. Title says the GVW is 9,000 lbs. It has a new Jasper E4OD with a gear ratio that makes it good for towing - I don't know what that ratio is, but I know my top speed is 70 mph or something (not that you'd want to go that fast with a motorhome anyway).

Pictures: http://rjmarq.org/airstream190/

I'm not the only one with a B190 that gets that kind of mileage - a few members of the B190 owner's group report similar results with the 460. Like I said, this is driving gently (55-60 mph, smooth starts, etc), no air conditioner, etc.

I should mention that I almost never drive that gently - I kind of enjoy suprising SUVs at traffic lights in the next lane - but even still, since the gas guage doesn't work reliably, I use 10 mpg as my estimate of what I'm getting to "dead reckon" when I need to get gas, and I haven't run out yet.

 

I see why you are geting better milage. You might want to run that across a set of scales and see what you do weigh. GVW is the maximum weight it is desined to be with load. You might weigh each corner sepratley to see if the weight is equal and that will tell you what kind of tyer and what inflation you should be using.
Bill

 

I've been wanting to weigh it. Do you know what it costs to have that done? (I also don't know where to have it done around DC...there's gotta be a truck stop or something...)

But - there's a fridge, a stove, an air conditioner, a microwave, a generator, fresh water tank, gray/black water tanks (though I usually travel with those empty), an awning, captain's chairs, and wood cabinetry that's nicer than what I had in my condo... Plus the walls and ceiling are all covered with fabric over particleboard. I'm sure it has a good deal of weight in there. Also, it's almost 10 feet tall, so wind resistance is a factor.

I've been trying to use the Ford recommended tire inflation (it's a motorhome chassis, so presumably they figured out a reasonable weight for it when coming up with the inflations) of 65 psi in the front and 80 psi in the rear, IIRC. But I'm having trouble finding an inexpensive air compressor that can accomplish that.

 

I would look in the phone book under public scales and call them and see what they charge. Some feed stores and big junk/recykling yards have then to.
Good luck
Bill

 

Truck stops are a great place to weigh your vehicle, and since you don't need a letter certifying your weight so you can avoid roadside weight checks, they might even do it for free.

 

Wow, 14 with a motor home and a 460???

My 84, 460, 4wd, 4:10 gears, 4k on the rebuild, edlebrock, 204 -214 cam (no overlap), thorley tri-Y headers, Holey 670 truck avenger carb, MSD 5, 4sp t-19 gets just under 8 mpg city and around 6 on the highway at 70mph (I track it closely every fill). Might pick up a little when it gets fully broke in but sheesh. I don't see how it will ever get up there without going to higher gears (lower numbers) which I'm not willing to change since I want low for off roading. I bleieve a good carb tuner can get me a little leaner safely, maybe a dist recurve, aside from that my motor was built to be one of those stump pullers and I am just a little dissapointed that my mileage is not slightly higher.

I guess what I'm saying is, 15 mpg seems a bit out there for a target based on my experience. Love to see it done, be sure to let us know how it turns out.

Jeff

 

Its called EFI and Overdrive. When done correctly you might be suprised what MPG you can get out of a bigblock.
Leadmic