FLOW JOB

摘要

Porting gets all the attention when it comes to preparing cylinder heads to rocket more air fuel into the chamber. Granted, a well planned and executed port job can turn stifling heads into free-flowing ones that allow an engine to be a more efficient air pump, but there's one small, but oh-so important detail that never gets the credit it should: the valve job.rnNo matter how good or bad a cylinder head's runners flow, the biggest impediment is always the valve. All that air rushing in from the intake has to slip through a tiny curtain of space that's equivalent to the area between the bottom of the valve at peak lift and the valve seat. That's why camshaft lift and duration are the two factors that can most alter an engine's performance and operating range; the larger the curtain and the longer it stays open, the more air and fuel can flow into the combustion chamber.