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January 2009 4x4 Tech Questions -Techline

Willie Worthy | Writer
Posted January 1, 2009

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Four Wheeler
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Los Angeles, CA 90048.

All letters become the property of Four Wheeler, and we reserve the right to edit them for length, accuracy, and clarity. The editorial department also can be reached through the Web site at www.four Due to the volume of mail, electronic and otherwise, we cannot respond to every reader, but we do read everything.

Engine Swap Options For Ranger/Bronco II
Question: I would like to upgrade the 2.9L V-6 in a '90 Ford Bronco II. I have heard that the 4.0L in the '91 Ranger/Explorer is the same motor with a larger bore and stroke. Will a 4.0L bolt in? What about a 289, 302, or 5.0L V-8? What is available for lift kits and suspension upgrades?
Nicholas Valpiani
Columbia City, OR

Answer: I have covered both the 4.0L V-6 swap as well as the V-8 swap several times in the past. In fact, we actually did a story on a 4.0 conversion (Oct. '97).

Yes the 4.0 is a direct descendent of the 2.8, 2.9, and 3.0 V-6, and it makes for a fairly simple engine swap. The V-8 swap is also doable, but a lot more work. With either conversion, a body lift kit is advised as then there is a lot less sheetmetal that has to be modified with a big hammer. You can find out more about the V-8 conversions by logging onto This site has a lot of great information in reference to Ford Rangers and Bronco IIs.

Leaky YJ Master Cylinder Fix
Question: As to the Techline question concerning a '92 YJ clutch master-cylinder leak (Sept. '08), the only "cure" is to use Girling or Castrol GT fluid. I went through this with my XJ and that worked. It is a Girling-based design (according to a Jeep insider), and the seals will bleed other fluids past them, seeping into the interior. Most people don't notice that it's seeping because they never look down there and it's not enough to drop fluid levels.
Thomas Confer
Salem, OH

Answer: You're so right, as were several other readers who caught this. I learned this trick back in the '70s-that you had to use nothing but Girling or Castrol brake fluid in a Girling-designed cylinder-when I was building sand buggies that used Girling brake cylinders and again found it to be true when I did a V-6 engine swap in the early '80s to a CJ-5 and then reconfirmed it with several Cherokees that I have owned. I have, in fact, mentioned this several times in past "Techline" columns. I am sure it has something to do with the rubber content compatibility with the additives in the fluid. I've been told that the fluid sold by Jeep dealers is also compatible (I would hope so!). My sincere apologies and a "Thanks" to those who caught it.

However, I still think that something is wrong with his linkage that is putting a side load on the cylinder, as even with the wrong fluid, they should last longer than the 2,000 miles he is experiencing.

Needs Better MPG From FJ-40 Cruiser
Question: I own a '73 FJ-40 with a Chevy 350, which is basically stock, with headers, Quadrajet, an SM420 trans, 4.11 gears, 35-inch tires, a winch, and a full 'cage. It's a heavy beast and my gas mileage sucks-8 mpg if I'm very gentle.

What can I do to help? Would Holley Pro-Jection be that much of an improvement, or would better heads and intake? Know of any diesel conversions, or is it time for a Honda Civic for a second car? By the time you factor in car payments and insurance, is it really worth it? Oh, and I drive 250+ miles a week.
Robert Castle
Tucson, AZ

Answer: In all reality, you should be getting a bit better than 8 mpg, but then again, you didn't tell me how fast you're driving; what's "gentle" to one person is not gentle to another. OK, to be honest with you, there is not a lot you can do about the fuel mileage. For example, I have a tube-framed, very modified flatfender Jeep with a mild 383 Chevy motor, 700R4 transmission, 4.56 gears, and a Quadrajet carb. Usually, there are some 36- or 37-inch tires on it. On the trail I get about 10 mpg. On the highway, it ranges from 10 to 13 mpg, depending on how much of a hurry I'm in. Nothing great either. One advantage that I have is that the trans offers an Overdrive gear, so my rpm drops about 600 when it shifts into Overdrive. Less engine speed equals better fuel mileage.

The first thing to do is slow down. Your Toyota is nothing more than a big square box with lots of wind-catching features. The springs, front and rear axles, transfer case, not to mention the flat grille, all cause the air currents to do strange things and cause an unbelievable amount of resistance. The second thing is to do the simple things-like make sure the air filter is clean, switch over to synthetic lubricants (not only in the engine but in the complete drivetrain), and by all means check out your exhaust system. Has trail damage smashed the tailpipe where it's causing a restriction? Lots of people don't think about this one. Pump up the tires to a higher air pressure to lessen the rolling resistance, though don't get too carried away to the point where the tires start to wear in the center of the tread.

Now, as to modifications to the engine such as fuel injection and better heads: most likely, yes, they will make a difference. How much? Maybe a couple of miles per gallon. Payback time? Probably about the time the vehicle is worn out.

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