The Definition of a Cylinder Head

Video Transcript

"Okay, this is a cylinder head right here, and this is for an overhead valve engine. And what you can see if we look at the top right here, the rocker arms actually attach right here. The valves come up through here. The valves have been removed. What you're looking at are the valve guide seals right here that keep oil from getting up past that and running over, and to also keep oil from going up inside the combustion chamber. If we look at this side of the cylinder head right here, these are the intake manifold passages. And they're actually cast inside the cylinder head. These outer two passages are coolant passages, so they actually have coolant circulating in the cylinder head around the combustion chamber right here. So this area right here is combustion chamber. The valves have been removed and of course the spark plug, but right here would sit and intake valve and that intake valve would correspond to an intake runner. So if can stick my finger right through it, you might be able to see that, my finger going through the passage right there. That's where the incoming air fuel mixture would go in. And then we have an exhaust valve. And I'll put my finger back through there and you can see my finger going back through the exhaust passage right there. So that's the combustion chamber. That's where the igniting of the air fuel mixture takes place, and it's done with a spark plug that's been removed. The spark plug is gone. I don't happen to see any around here that I can... oops. Here's a spark plug right here, and I don't know if... Yeah, you can see it poking in there. I'll just screw it in there for you real quick and you can see the spark plug. And that's a pretty well worn spark plug, but that's what ignites the air fuel mixture. So the fuel, as it comes in actually swirls around that spark plug, and at just the right instant is ignited, and once it's ignited it creates... rapid expansion takes place and the piston is forced downward and that actually spins the crank shaft in the engine. So a cylinder is a place where combustion takes place, and obviously a head on some modern engines are removable, whereas some of the heads on older engines were not... probably don't need to get into ancient technology there, but again we didn't have proper sealing on our early engines and you saw the head gasket right here. This is not off this engine. This is off of a V8. But the head engine is sandwiched between the engine block and the cylinder head to seal against compression losses and to seal against any coolant from getting into or out of the system, out of the cooling system or any coolant from getting into the combustion chambers, which would be a disaster. So that in a nut shell is a cylinder head. And you can see both sides of them right here. These are the valves lined up here. This is, you know, obviously going in through a valve surface overhaul, but that's what's going to take place here. So most engines use overhead valve, or our overhead valve where the actual valves are on top of the combustion chamber. Some of the early engines are side valve engines or L head engines and we actually have a couple of those engines. I don't know if the camera wants to take a look at some of those early engines. We can walk around a take a look at some of those. We can show you the difference. So L head or side valve engines are no longer made. They're not as efficient and not... the exhaust stream isn't as clean. The emissions are more difficult to control. And they're more costly to the manufacturer in a lot of respects, so... Okay we have a clean cylinder head coming up, a side valve. Is this off an Accord? Okay, this is of an Accord that uses lye combing engine. Right here this is an aluminum head, which is a very very early aluminum cylinder head. Again you can see the combustion chambers right here, very shallow. This is a high compression combustion chamber. You don't see any valves in here. This is a real simple head. All it contains is a combustion chamber, and it contains the cooling passages. That goes into the water jackets right there as we call it. And of course that's the other side of the cylinder head right there. This one's nice and clean because it's been media blasted to clean off all the crud off the cylinder head right here. And again it looks like it's been surfaced and cleaned up and will probably be put back in service again. But again a lot simpler. And these are the cutouts for the valves. The valves are in the engine block. They're not in the cylinder head on an L head engine or side valve engine so."