automotive engineering schools: April 2012

16 Valve Engine

The above pic is of an chain driven engine. Where we were working on belt driven.

We were supplied engines from Unitec Albany & ask to pull them apart & study what each part of the engine does.

Intake Valve's - The diameter is slightly bigger than the Exhaust Valve & burns clean.

Exhaust Valve's - Diameter is smaller & will burn a lot dirtier than the Intake Valve's. If you are not sure which on is which when pulling them apart - Wipe your finger around the Intake ports & the Exhaust ports, The Exhaust ports will be dirty & leave black marks on your finger. Where as the Intake ports are cleaner.

Intake:

Air + Fuel - Piston, Bottom Dead Center

Inlet valve - Open

Exhaust valve - Closed

Compression:

Inlet valve - Closed

Exhaust valve - Open

Piston, Top Dead Center

Power:

Piston, Top Dead Center

5 Degree - 9 Degree Spark

Inlet valve - Closed

Exhaust valve - Closed

Exhaust:

Exhaust valve - Open

Inlet valve - Closed

Piston, Top Dead Center

Stripping The Engine

Timing belt covers have been removed.

Removing a pulley.

Rocket cover has been removed.

What your looking at s the inside of cylinder head, top of the rockers.

Camshaft pulley at the top, which the timing belt attaches to.

Water pump attaches in the middle.

Next is the tensioner, Followed by the crankshaft.

The crankshaft pulley

This is how the timing is done, The belt attaches to the camshaft pulley & crankshaft pulley.

Using the grove & the arrow facing done to the grove.

Also by attaching a ratchet to the crankshaft bolt

To do the timing

To take the belt off, the tensioner needs to be loosened & pushed slightly to the right.

Once this done then the belt will slide off nice & easy

The belt been removed

Removal of the rocker shaft bolts

When removing these, they need to undone from the inside out in a circular motion. The same when you are tightening them.

Bolts & rocker shafts being/ been removed

Cylinder head bolts

When loosening these bolts there is a specific order they need to be undone.

The bolt that is being removed in this pic is number 9 bolt, second to last bolt to be removed.

This video shows how the cylinder head removes once the bolts have been taken out.
Also take in to count that there is still parts that need to be removed for the head to come right off.

The distributor
There is two bolts that hold this on.

The other end of the distributor that connects to the camshaft

End of camshaft where the distributor connects

Solid metal clip that helps hold the camshaft in place.
Before removing the camshaft this little clip will need to be removed & also the camshaft might need to be knocked out using a rubber hammer due to a rubber seal on the other end tightly holding this in.

After the camshaft is free to slide out, we then needed to to put a adjustable crescent on the end of the camshaft the is shaped like a bolt end. ( pic above)
And using the ratchet to undo the pulley bolt.

Removing the camshaft

Removing the spark plugs by using a ratchet, using the right sized spark plug adaptor to fit the end of the ratchet.

Spark plugs removed

The video on the right is showing how to remove the valves safely with out damaging anything.

Cylinder Head & Measurements

Theory:

The cylinder head is what seals the cylinder's forming a combustion chamber. It sits above the cylinder's on top of the cylinder block.

It holds the camshaft which operates the rocker arms to which will move the rockers. That will push down on to the Intake valves & Exhaust valves.

It also contains the spark plugs, Exhaust & Intake ports, Exhaust & Intake valves, Rocker arms.

Cylinder head allows the Fuel & Air flow to the cylinder & allows the Exhaust to escape.
The camshaft pulley is what the timing belt/ chain depending on the engine, is connected to which then pass's down past a tensioner & connected to the crankshaft that operates the pistons.

Experiment:

Carried out measurements of the Intake & exhaust valves using the micrometer - measuring six times at three points of the steam.At the top, In the middle & at the bottom - This is to find if Ovallity has a curd or if the tapered bit near the seat has been put out of shape.

Valve seat & margin - Using a vernier caliper to measure these two. If the margin is not at 1.0mm then the valve seat has worn bigger and valve will need replacing.

The length of the valves - using the vernier caliper - Under heat these can stretch and will cause the valve not to shut properly, which will make the vehicle to smoke.

Measuring of the head - Using a straight edge, light & feeler gauge. This is determine whether or not the head it self has warped in any possible way.

Visual inspections were necessary too, If there are any sharp point anywhere, scratches or even chips on the valve, Then this will seriously cause major problems. Also to see if the head of the valve, where the rocker's connect with, had created a sharp/ curvy edge. Hans explained this as "Bure"

Inspection of valve spring - Using the vernier caliper external measuring jaws, finding the free length of the spring. Free length has to be within 1.5mm of each other.

Inspection of valve spring installed height & seat pressure - With the vernier caliper tool & measuring 3 times at 3 different point.

Inspection of valve spring squareness - Take a square and place the spring against it & measure using the vernier caliper. A minus B will equal C - C being the over all squareness of the valve spring.

Inspecting the camshaft for wear & general condition - To do this we need the second smallest Micro meter. By measuring in two different position's on the cam lobes - ( A & B), A - being the the bottom of the lobe to the top & B - being the side's of the cam lobe. This is to determine the lift of each cam lobe. Our camshaft needs replacing as all the cam lobes didn't have the same lift.

Inspecting the camshafts journals - To do this we needed to use the dial tester. Setting the camshaft up on the "V" blocks and applying the dial tester to each journal of the camshaft. Once this done, then slowly turn the camshaft until the dial tester gauge starts to move. Then recording how much it the dial moves by. If it doesn't move then the camshaft journal is fine.

End-float readings - This is to determine movement once the camshaft has been installed. There should 0.57mm max movement as per specifications, Our camshaft has movement of .06mm, which is good. To do this we use the dial tester set up on the end of the camshaft where the camshaft pulley attaches.

There will be more measurements to put up as the exercise has yet to be finished.

Reflection On experiment:

The purpose of all of the above is to retain the knowledge of pulling apart, finding faults, knowing how or if the fault is fixable within the workshop or not. Then successfully putting the engine together.

We have discovered that the valve's are reusable and none of them need to be replaced but do need some workshop time on each valve. The head of each valve needs to be shaved back either 1 - 2mm each. This is to give the rockers more of a flat surface to push done on the Valves.

There was no warp of the the head which was good this means this does not need replacing. If it was warped then this could effect everything that works on the inside of the head from moving in a smooth operation.