Tech Q and A
I own a 1998 Jeep® Cherokee with the 4.0L inline six motor. It has over 120,000 miles on it. I would like to freshen the engine to be a powerhouse. What can be done economically and what Mopar® Performance parts are available?
MM: We’re assuming that when you say “freshen” you mean that you intend to rebuild it. And, although you didn’t specifically say so, we’ll also assume it’s a 4x4. You didn’t state your intended use of the vehicle, but a good place to start would be obtaining a copy of the Jeep 4x4 Performance Handbook (P5153769). This book has lots of great upgrade tips and other performance advice.
I’m only 16 years old, but I’m a huge Mopar fan. My family has a 1974 Dodge Power Wagon D-200 with a 400-cubic-inch engine and a four-barrel carb with no modifications. I was wondering what the factory horsepower and torque ratings are.
MM: Your 1974 Dodge Power Wagon with the 400 engine produced 240 horsepower at 4,200 rpm and 330 lb-ft of torque at 2,600 rpm. Just so you know, 1974 was the last year you could order true dual exhaust from the factory with this specific engine combination.
We don’t have a lot of daylight in northern Minnesota in the winter, so we rely on headlights a lot. A few days ago I saw a Dodge Ram, fairly new like a 2007 or 2008. Its headlights looked brighter and whiter than the lights on my 2007 Ram 1500. Are these factory lights?
MM: It used to be that headlights were headlights, but these days the aftermarket is full of choices from halogen bulbs to high intensity discharge (HID) lamps. As an example, Mopar is now offering SilverStar lighting products. SilverStar bulbs are brighter and whiter than basic lamps for better nighttime and low light visibility. The intensity of SilverStar lights is exceeded only by much more expensive HID bulbs. SilverStar halogen’s color temperature is a white-hot 4,000° K—far hotter than other halogens on the market and comparable to HID bulbs. Check them out at your local dealer.
Not long ago, I hit a deer in my 2007 Dodge Nitro. Most of the damage ($5,000+) was to the right front of the vehicle as the deer almost made it across the road. Now that I have it back, I’m noticing a pull to the left. Is it possible that a deer collision could be so bad that a vehicle can’t be repaired adequately?
MM: Car/deer collisions are quite common, especially in the northern part of the country, and they can cause a lot of damage as you discovered. But if your insurance company did not total your car, then it should be repairable to like new condition. First check tire pressure. A low tire can cause a vehicle to pull one direction or the other. If that doesn’t do it, take your Nitro back to the collision repair shop and find out if they performed a complete alignment. We can’t say conclusively, but a collision as you describe it would almost certainly require a vehicle alignment.
I usually see valve springs recommended along with camshafts. I understand more aggressive cam designs may need more valve spring pressure to control them, but often I see several springs recommended for a given camshaft, and pressure specs can vary quite a bit. What are the guidelines to help select the right springs? When is it OK to choose lighter springs, and what conditions require heavier springs?
MM: If you see several springs recommended for a particular cam, they will all work. A good general rule in choosing a spring from within a recommended range is to consider valvetrain weight. Production valves are usually heavier than high-performance stainless valves. Production and chrome-moly retainers are heavier than aluminum and titanium retainers. Stamped production rocker arms are heavier than aluminum roller rockers (with iron or steel mechanical or adjustable rockers somewhere in between). If your valvetrain tends toward the heavy side, pick a heavier spring.
I have a 1974 Plymouth Barracuda that I bought in 1978. The problem I’m having is that the steering wheel has a lot of play in it, and I was told that there is a way to adjust for that. I’ve seen replacement steering boxes but they seem expensive. Any suggestions? The wheels are original.
MM: Your steering wheel having play in it can be the result of any number of suspension components being worn. After more than 30 years this is to be expected. On some steering boxes there is an adjustment bolt with a lock nut that should be clearly visible in the engine compartment. This can be used to reduce steering play to a certain extent, but should not be considered a cure-all. Mopar Performance offers a manual steering gear worm and ball nut package (P4007612), if you are thinking about rebuilding a manual box (you didn’t specify if it’s manual or not). The package will improve the ratio to 20:1 compared with the factory ratio of 26:1. You should have a shop check the ball joints, tie rod ends, idler arm and any other front suspension items for wear before you replace the steering box.
I’m putting together a 1968 Barracuda that will be a pretty serious drag car, but occasionally driven on the street. My approach is to build a mild motor (around 400 horsepower small block) so I don’t have to run a lot of gear, converter or rpm. Do you recommend any little tricks I can use to be sure I’m not wasting power?
MM: We can break things down into three main areas to improve: drivetrain or chassis movement (flex); engine drag (or parasitic loss); and reciprocating weight. Getting the most engine output to the pavement means examining the path it takes to make sure little power is wasted along the way. You don’t want the engine, transmission or rear end moving around, so solid engine and transmission mounts will eliminate their movement. Polyurethane suspension parts will absorb less energy and let the car go where you want it. Chassis flex can also waste a lot of power—think of how much torque it must take to twist an entire car! This is where subframe connectors and roll bars or cages will really help stiffen the car up. Parasitic drag on an engine also robs a lot of power. Accessories create drag—components like A/C compressors and power steering pumps are driven by engine power, so toss those. In the weight area, eliminate anything unnecessary or unrelated to acceleration and traction. This is where lightweight wheels and tires, aluminum driveshafts and racing brakes come in. Every little bit helps!
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