【Listening】

【Vocabulary & Phrases】

【Reading】

BlockGroup

1. Engine Block

The engine block is the basic frame of the engine. All other engine parts eitherfit inside it fasten to it. It holds the cylinders, water jackets, and oil galleries.The engine block also holds the crankshaft, which fastens to the bottom of theblock. The camshaft also fits inside the block, except on overhead-cam engines(OHC). In most cars, this block is made of gray iron, or an alloy (mixture) ofgray iron and other metals, such as nickel or chromium. Engine blocks arecasting.

Someengine blocks, especially those in smaller cars, are made of cast aluminum.This metal is much lighter than iron. However, iron wears better than aluminum.Therefore, the cylinders in most aluminum engines are lined with iron or steelsleeves. These sleeves are called cylinder sleeves. Some engine blocks are madeentirely of aluminum.

2. Cylinder head

The cylinder head fastens to the top of the block, just as a roof fits over a house.The underside forms the combustion chamber with the top of the piston. The mostcommon cylinder head types are the hemi, wedge, and semi-hemi. All three ofthese terms refer to the shape of the engine's combustion chamber. The cylinderhead carries the valves, valve springs and the rockers on the rocker shaft,this part of the valve gear being worked by the push-rods. Sometimes thecamshaft is fitted directly into the cylinder head and operates on the valveswithout rockers. This is called an overhead camshaft arrangement. Like thecylinder block, the head is made from either cast iron or aluminum alloy.

【Speaking】

Role play the dialogue with your partner！

【随堂测试】