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May 2010 Techline

Posted in How To: Tech Qa on May 1, 2010 Comment (0)
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May 2010 Techline

Where To Write
Address all correspondence to: Techline Four Wheeler, 831 S. Douglas St., El Segundo, CA 90245. You can also reach us by e-mail at fourwheelereditor@sorc.com; be sure to type the words "Tech Line" in the subject line. All submissions 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.fourwheeler.com. Due to the volume of mail, electronic and otherwise, we cannot respond to every reader, but we do read everything.

Fuel Pump Mods For TBI Chevy V-8 Swap
Q I have a 1983 GMC with a four-speed transmission and a carbureted 350ci V-8. I want to take the 350 out of a 1990 Suburban with the TBI and computer. I think I have it all figured out except the electric fuel pump and return lines. The truck has dual tanks, and the Suburban doesn't. Any easy fix would be greatly appreciated. Also if there are any other fine points I may be missing, please let me know, but I think it is a pretty easy swap.
Aaron Buck
Trenton, FL

A That is a tough question, and the simple answer is: an external electric fuel pump as close to each tank as possible; a double-throw switch so one switch would control each pump; a control valve to open and close the fuel to either pump in front of or after the pump; and another control valve on each return line. Manual valves could be used, but the hose routing to put the valves in a reachable location might be difficult, so electrical valves would probably be needed. If you found a heavy enough rated switch, you could use one for everything or mount relays.

While it is tempting to use all rubber line for ease of routing, I suggest you use hard metal line as much as possible, as over time the rubber will degenerate due to weather and heat.

Maybe one of our readers has a better solution?

Disc-Brake Conversion For 8-Lug Dana 44?
Q I have a Chevy Dana 44 eight-lug front axle with drum brakes that I want to convert to discs. My question is, can the drum/spindle assembly be disassembled (i.e., like the full-floater 14-bolt), and Chevy eight-lug rotors attached to them without modifications? If not, what will I have to do to make this axle work?
Scott Chester
Hawkinsville, GA

A I had to think on this one a bit, and after a bit of research, was still not very sure of my answer. My first thought was, "Why not just exchange the complete front end?" But I'm sure you thought about that, so there may be some kind of problem with doing a complete axle swap. I had to have some help on this, so I went to Stephen Watson, owner of Off Road Design (www.offroaddesign.com). I figured that if anyone had the answer, he would-and he gave me the following information.

"Honestly, I don't know if you can take the drum off the wheel hub and just put a disc on it. I would guess not, since the spacing is probably different along with possible problems with the thickness of the drum versus disc center, stud differences, etc.

"One problem with drum-to-disc conversions that I am aware of is that the spindle bolt pattern on the knuckle is rotated different from the disc knuckles. The issue is that the caliper mount rotates with the spindle bolt pattern, and it moves the caliper up to where it interferes with crossover steering arms-and I assume it also interferes with a factory steering arm to some extent.

"The safe answer is to find everything from the knuckles on a disc-braked Dana 44 or GM 10-bolt and swap it all on, if you want to keep that Dana 44 centersection. If not, just run the whole disc brake axle.

"If you start sourcing just wheel hubs, you'll have to be careful because there was a spindle change in the 1/2-ton trucks, and I think there was a similar spindle change in the 3/4-ton trucks in the early '70s. It's probably safer to just keep the spindles and hubs together when swapping.

"This is probably not what you want to hear, but not much to do about that. It's hard to put much money into conversion parts when there's a chance to find a complete axle with better parts for a couple of hundred bucks."

"Another plus to finding a later-model disc-braked axle to use, or for parts, is that you have a chance to get away from the external-spline locking hub that's not terrible, but is less desirable than the later internal spline version. The newer housing may also be a larger diameter tube, though I don't know that would be a fact.

Tech Letter Of The Month
Wants 3/4-Ton GM Axles For CJ
Q I have a 1986 CJ-7 that I would like to convert to 3/4-ton Chevy Corporate 10-bolt/14- bolt axles. I would also like to do a springover conversion with the suspension. There are several goals that I need to accomplish. I need 33-inch tires and I want to keep the center of gravity as low as possible while lifting the Jeep.

What issues should I expect with the steering? Should I inboard the springs? Are reverse-wrap springs necessary for a springover? I am not sure if I will have over-width issues, but narrow tires and wheels should help. I hope to cover the rest with big flares. I know that I will need custom springs, steering components, etc., but which aftermarket suppliers offer Chevy axle-to-Jeep frame conversion products? Any advice you could offer on this conversion would be greatly appreciated.
Carmine DelliQuadri
Warren, Ohio

A No doubt about it: Full-width axles will cause the wheels to stick out way past the fenders. In fact, just about the entire tire will be out from under the fender with a standard offset wheel. I have seen a lot of people use wheels with lots of backspacing to narrow the track, but then you have the problem of the tires hitting the front springs when you turn if you go too far with the backspacing.

As to the springs, on a CJ the front springs have to be outboarded about two inches in order to clear the front differential housing. Blue Torch Fabrications (http://bluetorchfab.com) has a really easy way to do this. Their kit includes a new front bumper that incorporates the spring mounts, which they claim makes a much stronger mounting point rather than trying to add them off the side of the frame. Mountain Off Road Enterprises (www.mountainoffroad.com) also offers a kit that takes a slightly different approach to the mounting problem and seems to work just as well. Both of these kits are designed for a springover/reverse-shackle suspension system.

Keep in mind that you're going to have to do a few more things. For proper tie rod and drag link clearance, you probably are going to have to go to some different steering knuckles or add some high steer-type steering arms to the existing knuckles. You're also going to need a front driveshaft with a very long slip yoke to handle the extra rearward movement of the axle as the springs compress.

Keep in mind when deciding on what springs to use that you will gain about five to six inches of lift just with the springover conversion. It's pretty common to use the wider YJ-style springs in stock form or a mild lift. Naturally, you're also going to have to build new shock brackets both on the axle and on the frame. You might want to read the Jan. '10 edition of "Willie's Workbench," which dealt with springovers in depth.

Axle hop most likely will be a problem, and a military-wrap spring eye does seem to help along with a reverse wrap. I would advise some sort of a pivoting-link traction bar for the rear axle, such as the one Sam's Off Road sells (www.sams4x4store.com).

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