Engine rebuilding requires a high level of accuracy and offers little opportunity for mistakes. People make errors, but when they happen throughout the engine-building process, atonement is seldom as simple as hoping no one notices or begging forgiveness. Mechanical faults are not tolerated well by engines, which will let you know, sometimes by not producing the power you expect, and sometimes by a tragic breakdown. If you’re fortunate, you may be able to repair it or rebuild it from scratch. Other times, the whole endeavor is reduced to a heap of trash.
When creating an engine, there is no way to fully eliminate the risk of human mistake, but actions may be taken to reduce the risk. First, learn all you can about the engine you’re building. This is normally learned via experience, but even a novice may learn by studying service manuals, books, and articles on the topic. The next point to consider is preparedness. This involves having the necessary equipment, a clean, well-organized work environment, and clean, appropriately sized components. The last elements are the actual methods, techniques, procedures, and inspections used in rebuilding the engine.
Here are 8 mistakes you should avoid when working on a heavy-duty truck engine rebuild.
1. Insufficient rod bearing clearance
Not verifying the bearing clearance is an obvious one, and it’s a relatively regular occurrence. A builder may believe that a crank checks to standard specifications—if it is tested at all—and that the clearance is OK. One of the worst things you can do to an engine is over tighten the bearings, particularly on the rods, especially on a higher-rpm engine. When you spin them up, the rod stretches a little, pinching the bearing or not getting enough oil to keep it cool, causing the bearings to fail.
2. Finishing cylinder walls too smooth
Most people have learned that finishing cylinder walls too smooth is an issue. The crosshatch is meant to retain oil to keep the piston skirts and rings lubricated. If the wall is excessively smooth, the rings will not last as long and the piston skirts will be scuffed. To this day, we see a lot of engine builders make this error.
3. Going too large on the cam
Another frequent engine component selection error is going too large on the cam. We see this a lot, but we haven’t done that in a long time since we learned a long time ago that it’s better to go smaller than larger.
4. Excessive compression
Another issue we observe is that individuals use too much compression. For example, a client may bring in an engine that requires a 10.5:1 reduction and will be boosted with 15 pounds of boost using pump gas. The cylinder pressure must be compatible with the diesel used.
5. Pressed pins do not need lubrication
Engines with pushed pins are a common mistake that many men make. These are dry and are constructed by heating the rod while putting it together. When you put one of those engines together without enough oil on the piston and pin, it screeches to a halt the moment you start it up. We’ve seen some where you couldn’t spin the engine and couldn’t get it apart. They were all welded together.
6. Improper Cleaning
Insufficient cleaning of the block is a simple error, which is easy to avoid. A plug at the end of a blind hole in the engine may gather rubbish that is overlooked when the engine is cleaned. It’s difficult to clean an engine if you don’t remove all of the plugs. This is even worse if the engine is cleaned by baking and shot tumbling; if you don’t remove all of the plugs, you’ll discover an unbelievable amount of debris.
7. Rings that are stacked on top of each other
Rings are an essential aspect of your engine that should not be overlooked. A second ring that is turned upside down will pump oil like crazy. Another problem with rings is having the end gap too tight; you may go overboard on this. On the second ring, you may believe that a tight end gap is required, yet the contrary seems to be true. When the engine is larger, it runs dry (with less oil use).
8. Small cam clearing area
Cam clearing is an area that is sometimes ignored but may be costly. The cam will lock up if it doesn’t have adequate bearing clearance. Even when you’re trying to be cautious, it might happen; you know the housing bores are correct, and everything seems to be in order, so you put it all together. The cam (journals) may be a little big, and the bearings may be a little thick.
There are two types of engine-building mistakes: assembly errors and component selection faults. Keep all these mistakes in mind and ensure you don’t commit any of them.