Camshaft & Valve Train
How do you measure lobe lift?
Measure base circle of the cam and subtract it from the thickness across the cam lobe's highest point
What is valve lash?
The amount of space between the tip of the rocker arm and the tipoff the valve.
When does valve overlap occur?
While both intake and exhaust valves are open at the same time.
When adjusting valves, what section of the cam lobe must the lifter be against?
Base Circle (Heel)
What is valve lift?
How far the valve opens off of the seat
What is lobe lift?
How high the lifter moves up
What is an advantage of a roller lifter?
- Hardened roller on the bottom which rolls over a specially contoured cam lobe - Some type of anti- rotation guide system
List benefits of hydraulic lifters?
- Zero lash - Eliminates periodic valve adjustment - Eliminates lifter noise - Longer valve and cam lobe life by eliminating the pounding
How many camshafts are in a DOHC v-type engine, and what are they for?
4 camshafts 2 Exhaust and 2 Intake
What determines the useful power and torque range of the engine?
Camshaft
What is the size of the cam gear in relation to the crankshaft gear?
Camshaft runs at half the crankshaft RPM
What materials are crankshafts made of?
Cast steel, forged steel, steel billet
What are different cam drives that can be used?
Chain, Belt , Gear to Gear
What does concave mean?
Dished or cupped
What is valve duration?
How long the valve is open for, measured in crankshaft degrees
What is the purpose of valve overlap?
Improves volumetric efficiency
How do you calculate valve lift on an engine that uses rocker arms?
Lift x R.A.R
What will cause retarded cam timing?
Loose timing chain, jumped timing chain
How do you know where to line up the timing marks when installing a timing belt?
Manufacture Specs
Are all rocker arms adjustable?
No
If a lifter has concave wear, is it re-useasble? What should be done?
No, replace lifter and camshaft
Interference engine
Pistons may contact valves if timing is lost
What is the purpose of an anti-rotation guide?
Prevent roller lifters from rotating in the bore
What is the purpose of cam lobe taper?
Promote lifter rotation
What are two types of OHC engines?
SOHC- Single Overhead Cam DOHC- Dual Overhead Cam
What is valve overlap?
The number of degrees of crankshaft overlap
Non-Interference engine
pistons will not contact valves
