Different types of valve lifters are used in engines, including hydraulic and solid lifters. Each type has its own advantages and disadvantages, with roller lifters offering increased power and fuel economy potential but at a higher cost. Roller lifters also require stronger valve springs to keep them positioned on the camshaft lobes at high RPM.
The valve lifter follows the lobe of the camshaft in an engine and opens and closes the valves. The valve lifter, or riser as it is commonly known, comes in many different styles. Each style represents the type of camshaft that the lifter mounts to. There are hydraulic lifters in the pusher and flat roller types, as well as solid or mechanical lifters in the pusher and flat roller types.
Each type of valve lifter has its own positive and negative characteristics. The hydraulic flat lifter is the least expensive to purchase and perhaps the most common style of valve lifter used. It is mounted on the camshaft lobes and uses oil pressure to apply a slight preload to the pushrod. The positive aspect of this lifter is its ease of maintenance and use. The downside to this style of lifter is its ability to pump or float the valve at high engine RPM, or revolutions per minute.
The solid valve lifter in the form of a flat tappet also mounts to the lobe of the camshaft. However, this lifter uses a default clearance setting to operate the valve. The clearance is dictated by the camshaft manufacturer and is set on the rocker arm/push rod seat. The advantage of this lifter is its cost and ability to set the lifter clearance in RPM. The downside to this lifter is that it is noisy and needs continual adjustment to ensure proper operation.
Flat thrust camshafts and valve lifter assemblies produce friction and resistance to horsepower theft. They are often subject to wear and sometimes cause erratic valve timing due to extreme wear. The cure for this power-robbing system comes in the form of a roller camshaft and roller valve lifter.
The roller valve lifter incorporates a steel wheel at the base of the valve lifter. This wheel rides on the lobe of the camshaft. This design prevents friction and increases power. It also prevents premature wear. The roller style lift comes in solid or mechanical and hydraulic designs. This type of lifter requires a stronger valve spring to ensure that the roller remains in contact with the camshaft lobe at high engine RPM.
The benefit of a roller system is increased horsepower and fuel economy potential over that of a flat pusher system. The negative aspect of the roller system lies in the high cost. Also expensive is the increased pressure valve springs needed to keep the lifters positioned on the camshaft lobes.
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