Cylinder Head Component Description

Here's a group of pictures showing a cylinder head, valves, valve springs, lifters, followers/rollers/lash adjusters, and a few other cylinder head related pics. The components in these pictures will be of both DSM and non-DSM parts but will all use the same designs that we use in our engines.

Here's a cylinder head from the combustion chamber point of view:
1. Coolant Passage
2. Intake port
3. Spark plug hole
4. Exhaust port with valve in it

 

[Doug99RS]

1. valve seat, where the valve meets the cylinder head to seal the chamber
2. valve guide.

There there are multiple plains in the area of item one. When valves are reground with a performance/multi-angle valve job, the angle of the area marked in yellow is changed to match the new angle of the valve. The idea is that both are relatively the same angle to make sure it seals. Changing the angles (both) will increase the amount of time the valve is open without even changing the way that valve opens.

 

[Doug99RS]

These are the valves. Both have been used but the one on the right has been "lapped" in and is ready to reinstall. Lapping is a process shown in the next couple of pictures.

Note the dark ring that goes all the way around the valve on the left and how it is now a light gray on the right valve. Second note the multiple shades within that dark ring on the valve on the left. Those are areas that the valve did not seat completely all the way across it. If the entire ring was compromised in one section then it would no longer seal and would be considered "burned". This is a terminology used on valves that no longer seal the combustion flames inside the cylinder and create a mis-fire condition.

 

[Doug99RS]

1. Valve lappping tool with suction cups on each end
2. valve
3. valve spring
4. valve keeper/lock
5. valve spring retainer

 

[Doug99RS]

The valve keepers have notches that stick out and the keeper itself is half circle and tapered. The valve has grooves in it that match the notches that are on the keepers. Two keepers will surround the entire valve, grooves hold the keepers in place on the valve. The valve spring retainer has a surface for the valve to press against and a surface for the retainers to press against. As the spring forces the retainer upward, the keepers are forced upward. Since they are grooved and matched to the spring they can't go anywhere and thus lock the spring, the spring retainer, the valve, and the valve keepers all together to work as one assembly.

 

[Doug99RS]

This is the valve stem seal. It has three major parts to it. The wide collar at the base provides a surface for the valve spring to rotate on. If that were not there the spring would rest on the cylinder head. As the spring rotated it would wear in to the aluminum until it gouged the head and the spring stopped rotating. The next part is the rubber part. This is the seal itself and is responsible for keeping oil out of the intake and exhaust ports as well as keeping the oil side of the cylinder head sealed from the vacuum inside the intake ports and the exhaust on the exhaust port side. Without this seal the engine would both suck oil in and burn it as well as suck it out in to the exhaust and cause alot of oil smoke. The last part is the silver ring at the top of the seal. This is a spring that keeps pressure on the seal to clean the valves of oil as well as keep the seal in a round shape.

 

[Doug99RS]

1. Cylinder head bolt holes
2. Coolant passages
3. Supposed to have pointed coolant passages as well
4. Oil return hole
5. Coolant passage, high pressure
6. Sealing point of combustion chamber at the Head Gasket
7. Blown section of head gasket/cylinder head sealing surfaces.

This head came off of an 01 PT Cruiser 2.4L. The head design is nearly identical to the 2gnt and still very similar in design concept to the 4g63's. The coolant passages have been stained from the 5 year (red/orange/pink) coolant as well as light corrosion.

The valves on the top are the intake and the ones on the bottom of the pic are the exhaust. Note the different colors. The moisture on the middle cylinder should be ignored. But look at the exhaust valves on the two other cylinders. They are considerable lighter in color. This is because the intake valves are cooled down by the air/fuel charge. The exhaust valves are exposed only to hot temperatures from the combustion of the air/fuel charge and the removal of the hot exhaust gases. If you scroll back up to the third picture showing the two valves you can see light pitting on the valve on the left. This pitting is because of the high temperatures, carbon build-up and normal wear. If a valve cannot transfer or get rid of enough heat then it will burn the sealing face. If the valve fails to rotate, has carbon build up or continuously fails to seal in the same spot it will burn to the point of not being able to seal at all. This will cause a cylinder mis-fire in the form of poor acceleration, poor idle, sputter out of the exhaust, low vacuum and compression readings. The only repairs for this condition is to remove the valve and try and lap it back in (expect three to four times the amount of effort to do this), regrind the valve and valve seat on the head, or to replace it. The best option being. Defiant was able to shed some more light on the subject for me that I didn't know before hand. All of the valves use the sealing surface to transfer heat as well. So while a performance cut valve job will help get more air in to the chamber quicker, a smaller sealing surface will prevent optimal heat transfer causing a valve to burn quicker and pit easier.

Note the area in the red boxes. Item 6 is a good sealing surface because the coloration is uniform and equal. However, in area 7 you can see alot of different shades, incomplete sealing rings and if you look at the bottom section of item 7, just above the yellow line you can see where the coolant passage was compromised. This sealing area in question was the gray line that gently slopes upward and rounds back downward. Just before the peak in that box you will see a dark spot interupting the gray line. That's where the gasket blew out. In addition, most of the area directly in the middle of the two cylinders there is blown out as well.

Also check out the coolant passages marked as item 2. These passages are not only in the head but also extend in to the block. A quick inspection of the block side of these passages would show that they nearly completely surround the combustion chamber as it extends downward towards the oil pan. This allows the coolant to absorb the head from the combustion process. The coolant is then carried away by cooler water coming from the water pump.

A special note on coolant is that the water jackets are not smooth. This roughness causes the coolant to be agitated and create turbulance. This has good and bad points. If coolant simply flowed across a slick surface, there would be no side to side movement as it flowed across. The coolant closest to a hot surface is the only part that absorbs heat. Just image filling a tub up to about 60% capacity. Then turn on the hot water. Eventually the hole tub temp will equal out. But the hottest part will only be where the hot water is entering the tub. Now if you were to stir the water while it entered the tub you would have a more uniform temperature throughout the entire tub. So... now that you're done playing with your rubber ducky I'll continue with the engine's coolant description. SO turbulance and coarse passages are good for equal heat absorption.

The bad side to this turbulance is that it creates a static electrical charge. Friction causes a build up of electricity. This is obvious from our child hood days of dragging our socked feet across the carpet and sharing your newly found electrical personality with your best friends ear lobe while they weren't looking. Likewise the coolant builds up a charge as well. Most of it is able to transfer back to the block and then chassis ground. But there is still a good amount left in the coolant. This charge will increase engine corrosion in the form of electrolosys. We see this corrosion build up most frequently at the radiator cap, upper radiator hose to coolant filler neck housing, and at the water pump gasket areas. You can take a reading of this charge by using a multi-meter set in voltmeter mode. Simply submerge one end down in to the coolant and touch the other probe to battery/chassis GROUND. If you find a Zero to 0.2v charge then it's moderate to normal. However, if the charge is any higher then that you may want to change out your coolant to help reduce corrosion. Multiple flushes may be necessary to get out all of the coolant that has been charged.

 

[Doug99RS]

Below you will see another shot of combustion chamber section of the cylinder head. You can see a contrast between the coloration of the intake ports versus the exhaust ports. The intake again are cooler due to the fresh air and the cold fuel. It's also cleaner because the fuel acts as a cleaner and the air coming in has been filtered. This particular head has pretty low mileage on it because the coolant passages are not stained nor corroded, there's a light amount of carbon build up in the combustion chamber and there is little to no carbon/grime build up in the intake ports.

As the engine is run more and more deposits will build up. These deposits come from many sources. Small amounts of dirt will pass through the air filter. The crankcase (consists of everything between the oil pan, engine, cylinder head and valve cover) is exposed to freezing and scalding hot temperatures. Exhaust gases in the crankcase after the air/fuel charge is ignited also change from gases to liquids or solids. Because of the temperature changes, contamination build up, and vapors left in the crankcase a system was designed to help remove the vapors. This is in the form of the PCV system. It's repsonsible for keeping air moving through the engine oiling areas to prevent damaging vapors from staying in one spot. This PCV system gets fresh air from one fitting in the valve cover and is pulled through by engine vacuum. A hose goes from the intake manifold to the valve cover.

A down side to this pcv system is that the contaminants removed from the crankcase may deposit on the walls of the intake manifold, intake ports in the cylinder head and the combustion chamber. These contaminants can easily be cleaned by using things such as Mopar Combustion Chamber Cleaner (MCCC) or other cleaning products that are sprayed in to the intake path. Removing these deposits is crucial to achieving optimum air flow through the intake system and will help reduce carbon build up in the combustion chamber. Carbon and grime deposits will decrease air flow but can also cause un-even changes to the combustion chamber. Run a search on compression readings before and after using MCCC and you can see the number differences before and after using it.

 

[Doug99RS]

Alright so now you've got a basic understanding of most of the stationary components of the cylinder head. The next couple of pictures will be of the moving pieces like the followers/rockers, valve springs, lifters, cams and some not so pretty artwork I did to try and illustrate some of those pieces movements.

 

[Doug99RS]

You'll have to have a bit of an imagination for this next picture to work for me but here goes.

As the cam goes around in a circular motion it opens and closes the valves. This action is caused by changes in the cam lobe shape. The cam lobe shape is critical to valve timing in that one cam grind can open or close valves at different rates than another. Also, they can change the distance the valve travels from open to close.

Below is an attempt to illustrate the action of the followers (also referred to as rollers, rocker arms, roller rockers, and a number of other things) ride directly under the cams. They have a seat that the lifter pivots on, a roller bearing surface in the middle for the cam lobe to ride on, and seat for valve to sit in.

As the vam lobe presses down on the roller bearing surface, the cam will try and force down the entire follower. Because the lifter is pumped up with oil, it will not give (move). So the valve and spring assembly will be the part that moves. This movement opens and closes the valve to allow in the air/fuel charge and let out the exhaust after it's been combusted.

The lifter (lifter or auto-lash adjuster) is designed to take up any slack in the movement of the roller and valve. This will prevent any ticking (lifter tick) or excess clearance between the valve and the cam. This lack of clearance ensures that the desired affect of a specific cam grind is transferred directly to the valve. If the lifter doesn't do it's job then the tick will develop and in severe enough cases, the follower may fall roll out of position and prevent the valve from opening.

This picture shows the lifter on the left, the follower above it, the cam above that and on the right the spring/valve assembly. The red dot in the black object (representing the cam) shows the center point of the cam. If the cam were perfectly round, the red dot would indicate the center of it.

The valve set-up on the left shows the cam lobe before it starts to open the valve. The set-up on the right indicates a valve that has opened, a compressed spring, and a follower that has tilted downward as a direct result of the cam pushing on it.