Why do you need a roller cam in a tappet engine?
To build big horsepower you need to have a cam with a lot of lift to open those valves wide. A lot of cam lift will require a higher pressure valve spring, giving the roller cam/lifter the advantage over flat tappet cams for building higher horsepower engines.
What makes a flat tappet camshaft wear out?
Flat tappet camshaftscan only withstand so much valve spring pressure pushing the lifter against the cam lobe. As you increase valve spring pressure on a flat tappet cam, you increase wear on the cam lobe and the cam contact face of the lifter.
What happens when you increase spring pressure on a tappet Cam?
As you increase valve spring pressure on a flat tappet cam, you increase wear on the cam lobe and the cam contact face of the lifter. This is a limiting factor when compared to a roller setup. To build big horsepower you need to have a cam with a lot of lift to open those valves wide.
When does the exhaust cycle begin in a camshaft?
To curb pumping losses, valve opening prior to the piston reaching the bottom of its stroke is vital. Both conditions are simple in theory while conflicting in operation. Generally the exhaust cycle begins around 70° before bottom dead center. Typically in a traditional valve train the exhaust valve is somewhat slow to lift from its seat.
What happens when you install a larger camshaft?
When a larger duration camshaft is being installed, unless the lobe centerlines have been changed, the overlap will be increased. If installing larger camshafts in a turbo application, advancing the exhaust and retarding the intake will reduce the inherent increase in overlap caused by upgrading to a larger profile.
What happens when exhaust is oversized for timing and rpm?
Contrarily, an exhaust that is oversized for the selected combination of timing and RPM may fail to adequately scavenge the combustion chamber surpassing the desired combinations range. This reduces both the intake charge initiation as well as failure to thoroughly discharge the cylinder.
What’s the average valve overlap on a camshaft?
The goal to make valve overlap useful is maximizing power output to the RPM band the engine is designed for. Commonly overlap can range from 60° to more than 100° on a race application, a mild street application operating between 25° to 55°, compared to a stock engine of between 15° to 30°.