The timing belt connected the camshaft and crankshaft. The crankshaft rotates twice, for every one rotation of the camshaft. The cam and crank shaft are still deep in the engine.
The chain was pretty easy to take off. Noticing these dots is important for alignment.
Here is an older image of engine with the valve cover on.
Once the valve cover is removed the push rods, rocker arms, and the valves. There are lifters on the camshaft, that push up on the push rods, and this causes the rocker arm to lower. This pushes the valve down, opening the valve.
The rocker arm is a seesaw. When the push rod goes up the the valve goes down.
Above are two diagrams that show the how camshaft uses the push rod, and rocker arm to open ans close the valves. Each cylinder has two valves one is an intake valve, and the other is an exhaust valve.
The front of the engine still has three things we need to remove on it. The harmonic balancer is a special weight, that dampens the force between power strokes. The engine is a straight 6, and it is 4 stroke. Half the time the engine is on one power stroke, and the other half the time the engine has 2 power strokes (slight simplification).
The harmonic balancer is designed to compensate for some of the harmonics introduced by the crack shaft.
The harmonic balancer puller uses 3, or 2 bolts to attach to the puller. It also has a central thread. Tightening the central thread on the puller loads the tread in compression, which loads the bolts in tension, until the balancer is pulled off.
When the engine reaches a specified temperature the thermostat is designed to open letting coolant though the system. Engines run better when they warm up, and thermostats are a simple tool for letting engines warm up quickly and not over heat.
The thermostat housing (I always called it the goose neck) was relative easy for us to take off. It was incredibly rusty inside the housing. However, I believe the thermostat we removed worked fine, but we replaced it anyway.
The water pump is belt driven. The four bolts on the front of the pump are designed to connect a fan, and pulley. We replaced the water pump before reinstalling the engine.
The fuel pump is driven by a special lobe the cam shaft,
A idle engine speed is around 800 rpm (revolution per minute). That is 13.33, revolutions per second. That is a revolution every 75.19 milliseconds (1/13.33) seconds.
Every revolution, all the pistons stroke 2 times, and the pistons are on a 4 stroke cycle. The piston is able to traverse the length of the cylinder in 37.6 milliseconds, and that is at idle.
At an rpm of 4800 the piston complete a stroke in 6.2 milliseconds. That is very fast for a mechanical system, but that impressive to computer and electrical people it is kind of slow.
For us it was a big deal to take the intake and exhaust manifolds off. Before we could start taking the manifolds off we had to remove the vacuum inlet. Older engines use the vacuum presser to control many things, from power breaks to distributor advance.
At the time we were very concerned about the number of vacuum lines around the engine.
After the all the vacuum lines were off and documented, we started to remove the intake manifold. The bolts were in good shape, and it was not too difficult.
The exhast manifold was more difficult to remove because of all the rust around it. The heat the exhaust manifold experiences make it rust a lot more. I do not recall what the rail above each inlet does. (If someone on the internet knows please let me know).
That is what a jeep CJ7 4.2 Liter engine looks like with both manifolds removed. We put the valve cover back on to keep it clean. It looks like we put the bolts back in the block to avoid losing them. Next we will pull the harmonic balancer and take the water pump off.
Vehicles in in the 80’s an d early 90’s did not have computer controlled fuel injection. These older vehicles used vacuum pressures to adjust the timing. Vacuum lines are still used to power, Power Breaks.
The carburetor atomizes the gasoline. The gasoline air mixture will then be ignited in the engine below. Modern cars have fuel injectors and not carburetors.
Coolant is designed to cool the engine, however the coolant is also being used to cool the air into the manifold here. Cooling the air in the manifold will allow a greater mass of air in the cylinders (b/c cold air takes a smaller volume)
The engine is starting to look like a equipment, not a junk pile.
These are images of the new engine on the engine stand. The distributor is blue with 6 cables leaving it. The coil is to the left of the distributor with one cable leaving from the top.
Below is an image from the front of the engine. The alternator is on the left side of, and the A/C compressor is dangling on the right. The harmonic damper is below the fan, and partially obscured by the fan.
We also took images of the old engine currently in the jeep. It does not look very pretty, but it run reliably.
The image to the left is from above. There is an aftermarket K & N filter on the carburetor. The distributor is in the image below.
Neither of these look pretty, but they are impressive pieces of automotive engineering. With two engines we will have backup parts should anything go wrong.
One on the most enjoyable projects I ever did was a rebuild of a 1987 Jeep CJ-7. I was 15 years old, and excited to learn about cars. My dad also enjoyed working on cars. We bought the Jeep in thought ebay. It was located in Kansans city Missouri. We had a fly there and drive it back.
The Jeep was in okay shape. It didn’t break down once on the trip. The weather was cold on the return trip. We latter learned that in warm weather the jeep would die due to a fault ignition control module.
We enjoyed driving the Jeep for a couple of months before we started the engine rebuild.
We got the jeep and rather then taking the engine out, we bought a extra engine from a man known locally as “Nathan the Jeep Man”.
Above is an image of the engine while on the trailer. There is a great deal of work that will be required before the engine would be suitable to drive a vehicle.
The bell housing is on the left side of the image. The intake and exhaust manifolds are on the bottom part of the image. The radiator tubes , vacuum tubes, and wires wrap all around the engine.