All overhead valve engines __.
a. Use an overhead camshaft
b. Have the valves located in the cylinder head
c. Operate by the two-stroke cycle
d. Use the camshaft to close the valves
An SOHC V-8 engine has how many camshafts?
a. One
b. Two
c. Three
d. Four
Feb
The Correct Answer is Explanation is :
Question 1:
All overhead valve engines ______________.
Correct Answer: b. Have the valves located in the cylinder head
Explanation:
Overhead valve (OHV) engines are internal combustion engines in which the valves are located in the cylinder head, rather than in the engine block as in flathead or side-valve engines. This design offers better airflow, increased power, and greater efficiency. The placement of valves in the cylinder head allows for improved combustion chamber design and generally higher compression ratios.
Let’s explore the choices:
- a. Use an overhead camshaft – Incorrect. Not all overhead valve engines have an overhead camshaft (OHC). In OHV engines, the camshaft is typically located in the engine block and uses pushrods to actuate the rocker arms and valves. Overhead camshaft engines are a different category altogether.
- b. Have the valves located in the cylinder head – Correct. This is the defining characteristic of an overhead valve engine. The pushrods and rocker arms transfer motion from the camshaft (in the block) to the valves (in the head), which is why it’s called “overhead valve.”
- c. Operate by the two-stroke cycle – Incorrect. OHV engines are typically four-stroke, not two-stroke. Two-stroke engines have a completely different valve and intake/exhaust system.
- d. Use the camshaft to close the valves – Incorrect. The camshaft opens the valves, but valve springs are responsible for closing them. The camshaft lobes push the valve mechanism open, and once the lobe passes, the valve spring forces it closed.
Question 2:
An SOHC V-8 engine has how many camshafts?
Correct Answer: b. Two
Explanation:
SOHC stands for Single Overhead Camshaft. A V-8 engine has two cylinder heads (one for each bank of four cylinders). In an SOHC design, there is one camshaft per cylinder head.
So, for a V-8 engine:
- One camshaft for the left bank of 4 cylinders
- One camshaft for the right bank of 4 cylinders
That means a total of two camshafts in an SOHC V-8 engine.
Let’s examine the options:
- a. One – Incorrect. A single camshaft would only be possible if the engine had a single cylinder head (like in an inline engine), but V-8s are V-configured with two heads.
- b. Two – Correct. One per cylinder head, which matches the SOHC layout for a V-8.
- c. Three – Incorrect. There is no common engine configuration with three camshafts in a V-8.
- d. Four – Incorrect. Four camshafts are found in DOHC (Dual Overhead Cam) V-8 engines—two cams per head