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November 2007 4x4 Tech Questions - Techline

Posted in How To: Tech Qa on November 1, 2007
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Address your correspondence to:
Four Wheeler
6420 Wilshire Blvd.
Los Angeles, CA 90048-5515.

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 Due to the volume of mail, electronic and otherwise, we cannot respond to every reader, but we do read everything.

Question: I would like to convert my '91 Ford E-350 from a gas-guzzling 351ci V-8 to a four-cylinder diesel. I have an '86 Mitsubishi Fuso engine with 47,000 miles that runs beautifully. After that, I would like to convert it, of course, to four-wheel drive. Is there anyone who can help me with this conversion or supply conversion parts?
Frank Acello

Answer: Before you even think about this conversion, you should check and make sure such a swap is legal. Will it pass an emissions test? Within a year or so, Mitsubishi plans to shut down its engine shop and outsource engines due to fact that their current line of engines will not pass emissions testing. Your 21-year-old diesel engine, most likely, is not the cleanest-burning engine around.

The next thing is to find out what the parts availability situation is for this engine. My guess is that there are a lot of these engines still in operation, especially in Europe and Japan. One source for parts may be Tom's Truck Center, a Fuso dealer (888/507-5260).

I get the impression that this engine is used in some light delivery-truck and industrial applications such as forklifts. This means that there is a good chance that there may be an SAE-type bellhousing available that will make it easier to adapt to a standard transmission. However, you didn't say if your unit was a standard or an automatic. You may be better off using a matching Mitsubishi transmission, but then you're going to have the problem of adapting the transmission to the transfer case. In this instance, you might consider using a divorced NP205 transfer case. Yes, you would have to build another crossmember to hold the transfer case in place, but as it is, you're going to be building motor mounts and crossmembers to hold the engine in place anyway. I have never heard of anyone ever using this engine, and in fact can't seem to find much information on it. It's one of these swaps that reminds us that "just because you have a good engine, it doesn't make it a candidate for a good conversion."

Question: I see a lot of competitors in Top Truck Challenge 2007 with an NP203/205 transfer case. Is that a better setup than a 205 Chevy/205 divorced Ford? Will this give me any problems? If it works, do you know the gear ranges of the transfer cases?
Justin Folkman

Answer: The reason for the 203/205 combination is that the total overall length is so much shorter and lighter than using two separate 205s with a driveshaft or coupler between them. Off Road Design ( offers a kit that makes use of just the gear reduction unit of the 203 and bolts it directly to the 205 unit with a very narrow adapter plate. This gives the choices of a 2.00:1 or a 4.00:1 combination of low-range gear ratios (OK, in actuality the 203 is 2.01:1 and the 205 is 1.96:1).

Question: My '95 Grand Cherokee has an oil leak that seems to be coming from the oil filter. I have tried different brands of filters, and various stages of tightness with the filter, but it still leaks. Any ideas on how to solve this problem?
Anthony Smith
Los Angeles, CA

Answer: First, check to make sure that you didn't leave an old filter gasket behind on the filter mount. This can happen and will lead to an oil leak.

OK, the second thing to check is the oil-filter adapter that's mounted to the block. Take it off and lay it on a surface plate. OK, you don't have a surface plate handy. A pane of window glass works for this. If you can insert an 0.008-inch feeler gauge between the adapter and the glass, you have found the problem. That is all the warpage it takes to cause a leak.

The new adapter is under PN 53009219, and the gasket between it and the block is PN 53020461. Tighten the new adapter to around 50 lb-ft of torque, put on the new filter, and start the engine and check for leaks. Maybe you'll even want to check the oil level just to be on the safe side.

Question: I have been reading your magazine for a few years now and just love it, and first off, those who write in to complain about way too many Jeep articles and tech info can shove it. The way I look at it, that is obviously who is doing the most writing in and requesting info, so just follow the trend!

What would be the proper way of setting up dual carbs on my Chevy 350? All that is done to it right now is a set of Edelbrock headers, MSD ignition, dual 2 1/2-inch exhaust with 4-inch jetboat bottles on 3-inch tips. The truck is an '85 Chevy 3/4-ton 4x4 regular-cab longbox with an 8-inch Skyjacker lift with reversed shackles residing on 44-inch TSL Swampers, 4.56:1 gears, and Dana 60s.

I like the 350 that's in it, but just need to squeeze a li'l more power. Would there be any benefit to putting on a six-pack or are there solutions other than dropping in a new engine?

Answer: Well, to start off with, you're right. The majority of the letters we get are from Jeep owners, and the majority of the vehicles on the trails are Jeeps, but that doesn't make us Jeep-biased. That's what our sister magazine Jp is for-just Jeeps. We try to cover all vehicles.

Anyway, what is really hurting your performance are those 44-inch tires and only a 4.56:1 axle ratio. That's about the same as running a 31-inch tire and 3.23:1 gearing-but worse! Worse because the truck also has to push much more air out of the way because of the lift and the added rolling resistance of the tires due to more contact area as well as the weight. You actually need an axle ratio in the 5.38:1 to 5.86:1 range, as this will put the engine back in to the right rpm range where it can develop some horsepower and torque. Changing to this new ratio will make it feel like you added 100 hp to your engine.

As to the dual-carb setup-well, you pretty much have the right carburetor right now with the four-barrel Quadrajet. It's an excellent all-around street and trail carburetor. Most likely it needs a complete makeover to bring it back to a performance level. One place to check out is i-5 Automotive (800/526-9952,, for a replacement or a rebuild of yours.

I believe you could pick up an honest 10 hp by swapping over to one of the performance manifolds. Edelbrock has a Performer that's good from idle to 5,500 rpm, and the RPM Performer that's producing power from 1,500 to 6,500 if you decide to go with a cam change. Weiand's Action Plus and Holley's dual-plane are also good choices. If you don't want to keep your present carb, Holley's Truck Avenger works quite well. Just make sure the manifold you pick will match the square-bore bolt pattern. I have used both a modified Quadrajet and the Truck Avenger and found them both to work quite well, even on steep sidehill angles.

As to your question on the six-pack, I am assuming that you mean a manifold with three two-barrel carburetors. With modern manifold design, it has been found that a single four-barrel will outperform both dual four-barrel and multi two-barrel carb setups, plus you don't have all the linkage hookup problems.

If you also think that you want to make a camshaft change for even more hp, be sure to make the axle gear swap first. If you think that your truck is underpowered now, going to a performance camshaft with present gearing will almost make it undriveable. Whatever you decide on doing, don't over-carb or over-cam thinking that bigger will be better, as in most off-pavement situations, it's not.

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