I want to be looking at about 11-12 mpg is possible, with my truck which has 4.10's, C6, 4x4, and improve torque+HP, and keep it at as low RPM as possible, what is a good way to set this up, on a budget? My truck is an 87 F-250 4x4, 4.10, C6, 460, carburated.

 

There are one of two things that will give you that kinda of mileage. An overdrive or change out the 4.10's. Otherwise with the 4X4 and 4.10's, I doubt it will happen, maybe 10mpg.

 

I have an 86 F250 4x4 460 C-6 3:55 gears and I can get 9.5-11 MPG on a squeze empty and on the road. Towing our travel trailer about 7,000# I get 6-7 MPG. I have an Edelbrock Performer manifold with a 4160 Holley 600 CFM with a brown secondary spring, a set of Max-Jets 63.2 6.5 power valve. I want to go with a Lunati VooDoo Cam #638-61601 Holley states it will work with stock converters, A/C, Power brakes, STOCK valve springs in most cases, Excellent in oval port engines, IT MAKES 19" of VACUMN, DURATION @ .050 IN/EX 213/219, GROSS VALVE LIFT IN/EX 535/540 It says it has a SLIGHTLY noticeable idle. Great for performance oriented marine applications and heavy duty 454 Dually towing apps.
I share all this with you because I have been looking at the same thing you are better performance hopfully better mileage. I also have checked with Scott on this board and he feels going with DOVE-A or DOVE-C heads will help, Alittle more compression =s better mileage.

 

I found a used gear vendors under/overdrive unit, without adapter, for 300 bucks, is this a good deal for a used unit, or should i forget that idea? has anyone had any experience with these? good? bad? ugly???

 

Yes, the last complete one I saw the guy wanted $1300 as is.

 

Sounds like this just sold if i can find the money real quick.

 

btw its out of a ford motorhome that had a C6, so it will work in my truck, right?

 

Uh, don't think so. It was probably designed to couple up to the C6 and your transfer case is going to be in the way.
I'm really curious, can any one tell me how you would adapt an auxiliary gear box to a 4x4?

Richard

 

it doesnt work in four wheel drive, it automatically disengages, and one unit generally fits on multiple systems, it just needs an adapter, or at least thats how i understand it.

 

That is my understanding also.

 

Wow, wish that would fit on my highboy, but I think the intermediate shaft would end up being about 3" long...

 

In general terms you want to free up the airflow and maximize volumetric efficiency in the RPM range you will be using.

In more specific terms, your first, best investment will be some good headerslike a set of Thorley tri-Ys or some Gale Banks pieces. The Banks headers are about the nicest things I've ever seen (the header flanges are more than a half inch thick!). They are expensive, but they are built to last and have a proven track record.

Consider having your carb professionally rebuilt and tuned for low-rpm efficiency.

Make sure your ignition system is in tip-top shape. Rebuild it if you have the slightest doubt about it working properly.

A modest cam with little, if any, overlap. This is critical. Don't go overboard on the cam! Something like the Crane 350501, 353901 or, at most, the 353931. Anything more will become increasingly uneconomical.

I did some quick Desktop Dyno runs with these cams. I presumed a stock-ish 8.5:1 compression ratio, good headers with small (1-3/4" or 1-7/8"), no head work, a tuned carb, and a generally good overall state of tune.

With the Crane 353931, DD predicts 366 HP @4500 and 480 lb-ft all the way from idle to 3500 RPM. The torque line on the graph is dead flat across that RPM range.

With the 353901, DD predicts 365 HP @4500 and 490 lb-ft torque from idle to 3500 RPM. Again, the torque line is dead flat.

With the 350901, DD predicts 338 HP @4000 RPM and 515 lb-ft at 2000 RPM. Unfortunately, the torque takes an immediate nose dive and is down to 450 lb-ft by 4000 RPM.

Based on this prediction, the middle cam is the one for you. It maximizes torque over the most useful RPM range for your application, and does so without fuel-slurping overlap. The idle will be almost stock-smooth. Finally, it will be reliable and easy on other valvetrain parts.

It may not deliver ultra-mega MPG, but it will get the most out of what you have. Also, if you don't have manually operated front hubs, consider having them installed. Being able to completely decouple the front drivetrain will show a noticeable economy boost.

If you do a lot of highway driving, consider switching to a taller, skinner, all-terrain radial tire to minimize weight and rolling resistance. The all-terrain tread has less rolling resistance than an off-road style tread, the tires will weigh less (i.e. take less power to turn), and the extra height gives you the same effect as a taller gear.

Brad

 

BRAD JOHNSON,
I really appreciate your knowledge and input. You have given me some answers.

 

what about changing to say some mild flowmasters or magnaflows? and maybe a truck avenger 670 or possibly a 770, is there anything else that should be done with these mods, or is this about it? and will i be able to run on regular, or have to switch to premium?

 

Smaller carb is better for volumetric efficiency, by causing better atomization of the fuel because of high air velocities thru the carb at lower RPMs. As long as your compression remains stock, regular is all you need.