Tech Q&A
The editors of Mopar Magazine answers reader's technical and general service questions.
I have a 1974 Duster with a 318 engine and 904 automatic transmission. I recently got the engine running, but whenever I shift into gear (any forward gear) or reverse, the engine dies. It’ll keep running if I give it gas, but it’s not very smooth. Could this be a transmission problem, something else going on, or a combination of things?
MM: It’s always hard diagnosing problems such as this without actually working on the vehicle, but a few definite possibilities come to mind:
- Torque converter issue (converter not slipping at idle as it should).
- Improper idle air/fuel mixture (could be due to a vacuum leak, an improperly adjusted carb, or a carb that’s in need of rebuilding).
- Ignition timing issue affecting cylinder pressure (initial timing should remain the same whether the car is running neutral or in gear against the brake. If the timing retards when the car is dropped into gear, it can cause the engine to stall. Generally it’s more prevalent of a problem with big camshafts than with stock cams).
Also, you mention that you just got the engine running, which might be a good clue. If the car has been sitting unused for many years, our money would be on the carburetor or fuel system. When gasoline sits unused for long periods of time, it turns into gum and varnish. That can adversely affect the carburetor and the whole fuel system. A carb rebuild might be next on the to-do list.
I currently own a 1969 Dodge Dart Custom with an automatic and 318 V8. For the past little while, I’ve been noticing a bit of a lull from when I push down on the gas to when the car really starts going. The engine sounds like it’s doing a lot of work, but I’m not seeing much acceleration as a result. It never used to be like this. Any idea what could be causing this noticeable lack of power? I’m a college student and I rely on my Dart to get back and forth from home to school, so any suggestions would be greatly appreciated.
MM: There are several issues that can cause this, but 99 percent of the time it’s either failure of the accelerator pump in the carburetor, or failure (actually stuck) of the centrifugal advance mechanism in the distributor. If it’s the former, you need to rebuild the carb; for the latter disassemble, inspect, clean and lubricate the distributor advance mechanism. While you’re at it, points and condenser, along with spark plugs should be replaced. If the distributor repair seems like too much trouble, and if function is more important than 100 percent originality, now would be the ideal time to upgrade your car with a Mopar electronic ignition (P3690426). Also, basic items like clean air fuel filters should be confirmed.
I’m new to the Mopar world and just bought a 1974 Dodge Challenger with a 318 automatic. Unfortunately as I was driving the car home for the first time, the engine died and wouldn’t restart. I checked and it’s got fuel and spark. I only checked the coil, not the spark plug wires. Before I get in over my head, do you have any suggestions about how I should proceed? A buddy of mine said he recalls in the 1970s Dodge switched to plastic for the teeth on the timing gears for noise reduction and that over time they tend to become brittle and break apart. Any truth to that?
MM: It is true that most production engines in that time period had cam timing gears made from nylon-coated aluminum. Generally, sometime between 75,000 and 125,000 miles the timing gear would fail, which not only caused incorrect (severely retarded) valve timing and a loss of compression, but also sent nylon shrapnel throughout the engine. Our recommendation is to run a compression test as a first step to verify the failure. If failure is found, remove the oil pan and pickup, clean all the nylon debris, and replace the timing chain and gears with P5249267.
I have a 1989 Shelby Dakota with a slung rod. I’m wanting to put a 408 stroker in it. What oil pan will work and do you have any tips for the changeover?
MM: Oil pan choice would depend on which particular engine block your future stroker engine uses, but in all cases it has to be a rear sump pan. If you use a 318/340-based block, you can use your factory 318 pan P5249062. If your engine is based on a pre-1962 360 engine block, you’ll have to use P5249060. If you’re basing your buildup on a Magnum engine block, you must acquire a factory Magnum truck pan regardless of whether you’re using a 5.2L or 5.9L Magnum block. The only major tip that comes to mind regarding the changeover would be in the area of engine mount differences between the 318 and 340/360 engines. See the Mopar Performance Street Truck Manual (P5007522) for details.
I am just starting the process of building up a 1985 Jeep Cherokee. To be honest, this is my first attempt at this kind of thing, and I’m a little afraid of goofing it up beyond repair. I’ve got a lot of work ahead of me, but in the end I’m not looking for anything flashy or over the top. I just want a good capable vehicle that will get me off-road and back. Are there any reference books available that would help with such a project?
MM: We all have to start somewhere so there’s no need to be afraid. Your first stop should be your local Jeep dealer where you can get a copy of The Jeep Cherokee XJ High Performance Builder’s Guide by Eric Zappe. This excellent manual will help you build just the type of XJ Cherokee you’re looking for—one that’s comfortable in the mountains, the mud, the desert, the street and everything in between. The book offers tips on how to upgrade your Cherokee’s suspension, axles, differentials, engine, transfer case and much more. There are a lot of photos and illustrations that will help you along the way. Special sections include driving tips and recovery techniques. It also features a detailed account of a group of XJs navigating through the infamous Rubicon Trail. This book is a must have for your project. The part number is P5153878. You can also order it online at amazon.com.
