Automotive Engines

Part 6 (Valvetrain)

Valvetrain

The collection of parts operate the valves. The Valvetrain includes the various parts that

convert the camshaft's rotary motion into reciprocating motion at the valves, and the valves and their associated parts.

These parts include:

Valvetrain

1. Cam

2. Lobe

3. Lifter

4. Push Rod

5. Rocker Arm

6. Valve 1

2

3

4

5

6

Valvetrain Parts Cont.

Seals, Retainers/Rotators, Keepers Rocker Arms, Followers, Push Rods Guides, Seats, etc.

Cyl. Head Parts

Guides Seats Valves Springs Cups (Al. Heads) Retainers Seals Keepers Rockers

Valves

Made of:– Steel– Stainless– Titanium

Valve Spring

Generally a coil of wire, that closes the valve after it has been opened by the cam, and prevents the valve from bouncing on its seat.

Valve Retainer/Rotator

Retainer– Connects Valve to spring

Rotator– Rotates Exhaust Valves

to eliminate hot spots

Valve Spring Keepers

Cone shaped wedges hold retainers to valves

Rocker Arm

A reciprocating lever, generally used to multiply valve lift

Follower (OHC)

1. Follower: Similar to a Rocker Arm

2. Lifter

3. Valve

4. Lobe

12

3

4

Shim & Bucket (OHC)

Cam Acts on Valve Shim is removable Adjusts lash

Pushrods

Transfer lifter motion to rocker arm.

Most are hollow to transfer oil to valves & rockers.

Valvetrain – The End