© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Chapter 12 Upper End Theory and Service

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Cylinder Heads Made of cast iron or aluminum Contains valves, valve seats, valve guides, springs, rocker arm supports, and the upper portion of the combustion chamber Contains coolant and oil return passages Head design is one of the most influential factors in overall engine performance

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Cylinder Heads (Cont.)

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Cylinder Heads (Cont.) Intake and exhaust ports are cast into the head Most heads are aluminum to reduce weight Heads can have crossflow or Siamese port

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Crossflow and Siamese Heads

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Wedge Chamber – The spark plug is located at the widest part of the wedge Hemispherical Chamber – The combustion chamber is shaped like a half circle – The spark plug is located in the center of the combustion chamber Combustion Chamber Types

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Combustion Chamber Types (Cont.) Pentroof Combustion Chamber – Used in many modern engines – Modified hemispherical chamber design – Found mostly on engines with four valves per cylinder

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Wedge Combustion Chamber

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Hemispherical Combustion Chamber

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Pentroof Combustion Chamber

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Intake and Exhaust Valves Commonly called poppet valves Allow air to flow into and exhaust out of the combustion chamber Seal the upper portion of combustion chamber Intake valves are larger than exhaust valves

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Valve Construction Most valves are hardened steel, steel alloys, or stainless steel Intake and exhaust valves are usually made of different materials Valves can be one or two pieces Some exhaust valves are sodium filled Some high performance engines use titanium valves

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Valve Terminology

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. May be cast into or inserted into head Seals the valve and transfers heat Valve Seats

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Valve Guides Support the valve and allow only up and down motion Close clearance to valve stem Keeps valve aligned with valve seat Can be cast into or insert into the head

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Valve Guides (Cont.)

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Valve Spring Retainers and Oil Seals

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Rocker Arms and Pushrods Change the direction of the cam’s lifting force Pushrods link the cam to the rocker arm

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Cam Followers Used on some OHC engines Can be used to hydraulically adjust valve lash Increases contact between cam and valve

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Camshaft Bearings Most OHC cylinder heads are machined for the camshaft to ride directly on the head

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Knowledge Check Technician A says the part of the valve that moves through the guide is called the valve face. Technician B says the part of the valve that moves through the guide is called the valve stem. Who is correct?

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Multivalve Engines Used to improve airflow in and out of combustion chamber Larger valves require increased spring tension Three, four, and five valves per cylinder used – Four is most common

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Variable Valve Timing VVT can be intake only, intake and exhaust, or vary lift and timing of all valves Staged systems allow two valve timing and lift settings – Honda’s VTEC Continuously variable systems change cam phasing

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. VVT Phaser

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Fiat MultiAir Provides variable lift and duration of intake valves PCM controlled hydraulic solenoid controls valve opening

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. BMW Valvetronic System Varies intake valve lift Combined with VANOS, provides variable lift and valve timing

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Cylinder Deactivation Keeps valves closed on specific cylinders Decreases the working displacement OHC engines may lock and unlock the rocker arms OHV engines deactivate lifters – Chrysler and GM displacement on demand

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Cylinder Head Disassembly On some OHC engines, the rocker arms must be removed first Remove the camshaft Keep bearing caps and follow assemblies in order

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Knowledge Check What are two advantages gained by using VVT systems in modern engines?

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Cylinder Head Disassembly (Cont.) Measure spring installed height before disassembly

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Cylinder Head Disassembly (Cont.) Use a socket and mallet to loosen the valve keepers Attach and adjust the valve spring compressor Compress the spring and remove the keepers Remove retainer, spring(s), and seal

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Compressing Valve Springs

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Cylinder Head Inspection Replace a head showing severe damage to valve sealing areas Check for dents, scratches, cracks, and corrosion damage Check intake and exhaust manifold mounting surface flatness

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Measure Head Warpage

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Cylinder Head Inspection (Cont.) Inspect aluminum heads for porosity leaks Check head thickness and compare to specifications Check OHC style heads for proper cam bore alignment

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Valve Inspection Check each valve face for signs of burning Discard any valves that are burned, worn, bent, or has the plating flaking off or chipped Look for oil buildup on the back of the valve

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Inspect the Stem for Wear

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Valves Seats Inspect for damage, burning, cracks, and deterioration Check for loose seats Inspect for sunken valve seats Seats should be replaced if the valve was broken or bent

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Checking for Loose Valve Seats

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Retainers and Keepers Worn retainers will allow the spring to move away from the valve centerline Uneven wear on the stem tip indicates rotators not working properly

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Valve Springs Check for cracks, breaks, damage, and rust Perform tests to determine valve spring condition – Freestanding height test – Squareness test – Open/close pressure test

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. (A) Freestanding height (B) Closed valve spring height (C) Open valve spring height

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

Inspection of the Valve Train Timing Belts – Normally replaced when the engine or head is rebuilt – Ensure there are no fluid leaks that can damage the belt Timing Chains – Measure chain for stretch Idler Pulleys – Check for smooth operation and lubricant leakage Tensioners – Check for smooth operation and lubricant leakage

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Gears and Sprockets – Check for cracks and tooth wear Cam Phasers – Perform air testing of advance and retard action Cam Followers and Lash Adjusters – Check for movement of shim Inspection of the Valve Train (Cont.)

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Rocker Arms – Inspect contact points and oil feed hole Pushrods – Check oil passage and for straightness Camshaft and Bearings – Inspect lobe and bearing journals – Check cam straightness Inspection of the Valve Train (Cont.)

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Knowledge Check What are three conditions valve springs are checked for?

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Cracks are common between spark plug bore and valve seat Cracks between seats are also common Servicing Cylinder Heads

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Resurface – Makes the sealing surface flat so the gasket seals properly – Raises the compression ratio – Squares the deck to the main bores Resurfacing a Cylinder Head

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Stock Removal Guidelines Resurfacing reduces combustion chamber size – increasing compression ratio Reduced head thickness changes valve timing May reduce valve-to-piston clearance Intake manifolds on V-type engines may not align

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Valve Face Valve face angles and dimensions must be kept within specifications

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Valve Stem Grinding the face sets the valve lower into the port – extending the stem height

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Valve Stem (Cont.) If stem height is excessive, the valve stem tip may be ground Chamfer valve tip after grinding Valve and/or seat may need to be replaced to correct incorrect stem height

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Valve Guide Clearance Measure the guide diameter and stem diameter

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Inadequate Lubrication – Is caused by oil starvation in the upper valve train Valve Geometry Problems – Lead to increased guide clearance, poor valve seating, and premature wear Wrong Stem to Guide Clearance – Can cause increased oil consumption Valve Guide Problems

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Valve Guide Reconditioning

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Valve Guide Height Important to avoid interference with valve spring

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Reconditioning Valve Seats Seat must be correct width and in correct location Important for heat transfer Seating pressure reduced on wide seats Seats may be ground or replaced

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Measuring Seat Width

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Valve Seat Grinding Seats are ground at an angle to the valve face Many seats are cut with three angles

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Checking Valve Fit Coat valve face with prussian blue Snap valve open and closed against seat Inspect the pattern of the dye

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Valve Lapping Uses an abrasive compound to remove small imperfections in valve face/seat contact area

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Valve Stem Seals Control the amount of oil between the stem and guide

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Knowledge Check A valve seat that is too narrow may cause insufficient transfer from the valve to the head.

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Assembling the Cylinder Head Installed stem height and installed spring height must be checked Stem height affected by valve and seat Spring height may be adjusted using shims

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Assembling OHC Heads Camshaft full round insert bearings are pressed into the head Do not use an OHV cam bearing tool Some OHC engines do not use insert bearings Coat all rockers, adjusters, pushrods, lifters, and other parts in oil for assembly Adjust valve lash and install head