Q: What is the difference between a flat tappet and a roller camshaft?
A: Camshafts are classified by the type of lifter they use.
The lobes on the cam are machined differently based on the intended lifter. Lifters are sometimes called a “follower” or “tappet.” They contact the cam lobe with either a flat surface or a wheel.
Flat Tappet vs. Roller Camshafts
Flat Tappet Lifters
In reality, flat tappet lifters are not flat. They actually have a slight crown on the face. The camshaft lobe is machined with a mild taper. This causes the lifter to spin as it rides on the lobe and ensures even wear on the two surfaces.
Flat tappet cams are widely used, perform very well, and are more affordable than a roller cam.
When changing cams, the flat tappet lifters will need replaced. Follow this link for details on replacing lifters.
Lifters for roller cams feature a wheel supported by needle bearings and an axle. This wheel is attached to the bottom of the lifter body. The lobes of roller camshafts are machined perfectly flat. Roller lifters are linked together, or anchored somehow, to prevent them from spinning.
Roller lifters minimize friction which provides more power.
This design wears less, which leads to longer life. Roller lifters also allow for steeper cam lobes. In other words, they allow for more “area under the curve.”
This means the valve opens faster and remains at a higher lift for a longer period of time. This lets more air and fuel into the cylinder, which provides more power.
When changing cams, roller lifters can be re-used. Follow this link for details on reusing lifters.