1 Camshaft Locations 1) Cam-in-block: dated technology (but still widely used) dated technology (but still widely used) more moving parts more moving parts valve movement is less precise valve movement is less precise can be noisier due to more moving parts can be noisier due to more moving parts

2 Camshaft Locations 2) Overhead Camshaft: OHC, SOHC, DOHC OHC, SOHC, DOHC more precise valve action more precise valve action has replaced cam-in-block has replaced cam-in-block

3 Variable Valve Timing to enhance breathing over a wider rpm range, and thereby increase torque, manufacturers may design engines with either a,b,c or a combination of a,b,c…to enhance breathing over a wider rpm range, and thereby increase torque, manufacturers may design engines with either a,b,c or a combination of a,b,c…  a) variable valve opening timing  when the valve opens  b) variable valve lift  how much it opens  c) variable valve opening duration  how long the valve is held open BMW Honda

4 Variable Valve Timing Fig. a Fig. b Fig. c

5 Engine Block & Cylinder Head Materials materials used in engine blocks and cylinder heads construction are… materials used in engine blocks and cylinder heads construction are… Cast iron Cast iron  heavy  inexpensive  painted Aluminum Aluminum  lighter than cast iron  $$$  unpainted  warps more readily when overheated Magnesium has recently been used as well (BMW) Magnesium has recently been used as well (BMW)  lighter than aluminum engines can be engines can be  all cast iron  all aluminum or…  cast iron block & aluminum head (fig. a) fig. a

6 Exhaust Smoke blue smoke: oil entering the combustion chamber & burning along with air-fuel mixtureblue smoke: oil entering the combustion chamber & burning along with air-fuel mixture  worn valve seals and or worn valve guides  usually noticeable on initial start-up  noticeable on standard transmission equipped vehicles when changing gears  worn oil control rings and, or cylinder walls

7 Exhaust Smoke white smoke (excessive amounts): coolant entering combustion chamber & burningwhite smoke (excessive amounts): coolant entering combustion chamber & burning  “blown” cylinder head gasket  usually the result of an overheated engine  crack in cylinder head or possibly engine block

8 Exhaust Smoke if cracks are suspected, head and/or block will have to be checkedif cracks are suspected, head and/or block will have to be checked  aluminum: checked with a dye (fig. c)  cast iron: magnafluxing makes cracks visible  pressure testing will produce bubbles from the cracks (fig. a) cylinder heads should always be checked for warpage with a machinist’s straight edge & feeler gauge (fig. b)cylinder heads should always be checked for warpage with a machinist’s straight edge & feeler gauge (fig. b)  excessive warpage will require the surface to be machined Fig. a Fig. b Fig. c

9Noises ticking sound: valve train noiseticking sound: valve train noise  solid lifters: adjust valves (fig. a)  require adjustment at each tune-up  similar to small engines  hydraulic lifters: replace (figs. b & c) 1. quieter 2. able to adjust for thermal expansion of the engine 3. built in shock absorber, eases stress on valve train 4. should not require periodic adjustment Fig. a Fig. b Fig. c

10Noises deep metallic knocking sound can be the result of…deep metallic knocking sound can be the result of…  worn crankshaft main bearings  worn connecting rod bearings  low oil pressure

11 Poor Performance low compressionlow compression  valve and seat problems  cylinder & compression ring wear  ridge reamer needed before piston can be removed

12 Poor Performance can also be caused by…can also be caused by…  camshaft drives that are out of time  usually caused by worn components that have “jumped a tooth”  Remember: cam and crank MUST be timed on all engines!!!

13 Leaks - Oil always investigate oil leaks “top down”always investigate oil leaks “top down”  valve cover(s) (a)  students can confuse this for head gasket  cylinder head gasket (b)  oil pan gasket (c)  front crankshaft seal  rear crankshaft seal (d) steam clean the engine firststeam clean the engine first test PCV system – valve, hose etc.test PCV system – valve, hose etc.  if it’s not working, pressure will build in engine & cause leaks a b c d

14 Valve Service

15 Hey Roger, can your students fix it for me? Minor/doable (depending on the vehicle) repairs…Minor/doable (depending on the vehicle) repairs…  cylinder head gasket replacement  timing chain, belt, gear replacement  engine re & re (with a used one) Major Repairs…Major Repairs…  “low cost” rebuild  hone cylinders & new rings  valve grind  new camshaft  new rings, timing belts or gears & bearings  all new seals & gaskets  full engine overhaul  bore & hone cylinders  grind & polish crank  valve grind  new valve guides  resurface head(s)  new rings, timing belts or gears & bearings  all new seals & gaskets Consider…Consider…  how long can the vehicle be left in you shop?  do you have a machine shop you really trust?  how much $$$ does the owner have?  tackle only what you are comfortable with  good used original engines are often better than rebuilt engines