Quiz 3 - Upper Engine/ Timing Components Review

Both Technician A and Technician B are correct. Worn valve stem seals can indeed increase oil consumption as they allow oil to leak into the combustion chamber, where it is burned along with the fuel. This leads to higher oil consumption. Additionally, worn valve stem seals can cause valve deposits as they fail to properly seal the valve guides, allowing oil to enter and accumulate on the valve stems. Over time, this oil can form deposits on the valves, affecting their performance.

Multiple valve engines tend to be more efficient than engines with two valves per cylinder because they allow for increased port areas, provide more valve area, and provide less restriction to the airflow. By having more valves, the engine can intake and exhaust gases more efficiently, leading to better combustion and power output. The increased port and valve areas allow for improved airflow, reducing restrictions and enhancing engine performance. Therefore, all of the given options contribute to the increased efficiency of multiple valve engines.

When a timing belt or chain breaks, the synchronization between the camshaft and the crankshaft is lost. This means that the valves and pistons are no longer in sync, leading to a collision between them. As a result, the valves can get bent due to the impact with the pistons. This is the most likely type of engine damage that can occur when a timing belt or chain breaks.

Both Technician A and Technician B are correct. Checking camshaft wear can be done using different methods, and both a micrometer and a dial indicator are valid tools for this task. A micrometer measures the dimensions of an object with high precision, allowing Technician A to accurately assess the wear on the camshaft. On the other hand, a dial indicator measures small distances and displacements, which can also be used to detect camshaft wear. Therefore, both technicians can use their respective tools to successfully check for camshaft wear.

The typically acceptable maximum amount of warpage on an average cylinder head is .005 inch. This means that a deviation of up to .005 inch from the ideal flatness is considered acceptable. Any warpage beyond this limit may cause issues with the cylinder head's performance and fitment, leading to potential leaks or other problems.

Both Technician A and Technician B are correct. Positive valve stem seals do fit tightly around the top of the valve stem to prevent oil from leaking into the combustion chamber. Additionally, positive stem seals also scrape excess oil off the valve as it moves up and down, preventing oil from entering the combustion chamber and causing excessive oil consumption.

When the camshaft is worn to the point of replacement, both the valve lifters and the timing drive components should be replaced. The camshaft is responsible for operating the valves in an engine, and if it is worn, it can cause issues with the valve lifters. Additionally, the timing drive components, such as the timing belt or chain, are connected to the camshaft and can also be affected by wear and tear. Therefore, to ensure proper functioning of the engine, both A (valve lifters) and B (timing drive components) should be replaced.

Both Technician A and Technician B are correct. Timing chains are indeed provided with splash lubrication. This means that as the engine rotates, oil is splashed onto the timing chain, providing lubrication to reduce friction and wear. On the other hand, Technician B is also correct in stating that timing gears should always be replaced as a set. This is because the timing gears work in synchronization with each other, and if one gear is worn or damaged, it can affect the performance and timing of the engine. Therefore, it is recommended to replace all the timing gears as a set to ensure proper functioning of the engine.

The recommended timing belt change interval mileage is typically between 60,000 to 100,000 miles. This is because timing belts can wear out over time and mileage, and if not replaced within the recommended interval, they can break, causing severe engine damage. Therefore, it is important to follow the manufacturer's guidelines and have the timing belt replaced within this mileage range to ensure the proper functioning of the engine.

Neither Technician A nor Technician B is correct. Timing belts are not typically stretched into place using a pry bar. They are usually installed using proper tools and techniques to ensure proper tension and alignment. Additionally, timing belts should not be lubricated. They are designed to operate without the need for lubrication, and adding lubrication can actually cause damage to the belt and other components.

The idler shaft sprocket typically would not have a timing mark because it is not directly involved in the timing of the engine. The idler shaft sprocket is responsible for maintaining tension on the timing belt or chain, but it does not dictate the precise timing of the engine's valves and pistons. Therefore, it does not need a timing mark.

Hydraulic lifters must have manually adjustable valves. Hydraulic lifters use oil pressure to automatically adjust the valve clearance, but over time, the oil can break down, causing the lifters to lose their ability to self-adjust. Therefore, manual adjustment is necessary to maintain proper valve clearance and ensure optimal engine performance. Solid lifters, on the other hand, do not require manual adjustment as they do not rely on hydraulic pressure for operation.

The camshaft rotates at half the speed of the crankshaft.

When one hydraulic lifter is collapsed and causing valvetrain noise, the most likely cause is one worn or dirty lifter. This means that the lifter has become worn out or has accumulated dirt or debris, leading to its collapse and the resulting noise in the valvetrain. Low or high oil pressure, as well as incorrect valve timing, are less likely to be the cause in this scenario.

When all of the hydraulic lifters are collapsed and causing valvetrain noise, the most likely cause is low oil pressure. Hydraulic lifters rely on oil pressure to function properly and maintain the correct valve clearance. If the oil pressure is low, it can result in insufficient oil reaching the lifters, causing them to collapse and create noise in the valvetrain. This can occur due to various reasons such as a malfunctioning oil pump, clogged oil passages, or low oil level.