Valve tappet: description and photo

In any internal combustion engine there is a system of valve timing. It includes a chain or belt drive, gears, intake and exhaust valves. The latter regulate the supply and output of the fuel-air mixture, which burns in the cylinder chamber. The engine's pusher is also used here. What is this device and what are its features? About all this - later in our article.

Characteristic

The valve tappet (VAZ including) is an element designed to transfer forces to the rod from the camshaft. Modern cars use barrel-shaped mechanisms. They are made of cast iron. But, as the valve tappets (Ford Focus 2 is no exception) are under load, their lower part is tempered during the casting process. This ensures a reliable support surface for the cam. The barrel-shaped valve pusher has small holes, due to which the lubricant circulates. Also, these elements differ less in weight than in mechanical ones. To adjust the thermal gap on it a special bolt is provided. At the end of the article, we'll look at how to do this. Barrel elements are suitable for vehicles with valves located at the top of the unit. The lower end of the element is located in the recess, and on top of it acts the rod of the valve pusher. But regardless of whether it's hydraulic or a mechanical element, both types work in the cylinder block itself. Old Soviet-made cars installed a valve pusher of a different design. They were made from non-hardened steel and placed in a demountable pusher block. The latter was attached to the cylinder block on bolts. Curved convex profiles are provided on the element cams.

Other varieties

Some valve tappets are equipped with cams with a straight profile. Such elements are used together with rollers. The latter rotate on the axis. Now, such solutions are used only on high-speed engines. Due to the high probability of slippage, the roller rotates faster on the flange than near the flat base. The cost of such a design does not differ from other analogs. However, there is a big drawback here. During operation, the axle of the pusher is significantly worn out. The element is entrusted with large shear loads.

About a flat base

The valve pusher of this type rotates on its guides. What does this give? This reduces the slippage between the pusher and the cam. Also reduces the wear of the distributor. It is more even. As for the elements of the roller type, they should not rotate on their axes with rounded ends.

Hydraulic

The whole process of engine operation is accompanied by a large heat release. And since most of the mechanisms of the power unit is made of metal, it will tend to expand. Accordingly, the thermal gaps change, especially on the valves. After all, they let the combustible mixture into the chamber and let out the heated exhaust gases outward. To smooth out the arising noise during operation, modern engines use a hydraulic pusher. It compensates for gaps when the operating temperature of the unit increases and decreases.

How are they arranged?

In the body of the hydraulic pusher there is a plunger. In the latter there are two cameras. This is an injection and feed chamber, which receives lubricant from the engine during operation. Further, this oil passes through the ball valve to the discharge part. To compensate for gaps with high accuracy, the liquid volume is dosed in the plunger. It is pushed out of the body of the pusher spring. Thus, the thermal gap is restored to normal values. During the opening of the inlet or outlet valve, the oil is in the discharge chamber. The ball valve returns part of it back to the feed chamber. When the pusher body moves upward, a certain fluid pressure is created. The oil does not allow the plunger to move relative to the body. When the valve closes, the lubricant leaks from the plunger side. However, with a new discovery, this defect is compensated through the pressure chamber. When the engine starts, the elements of the gas-distributing mechanism gain operating temperature. The metal expands, and the volume of oil in the injection chamber decreases. Thanks to the harmonious operation of the mechanism, the gaps between the valves are compensated. Also in the work elements such as rocker arm and rod are used. Below we will consider what they are.

Rod and rocker arm

The first element is a metal tube with a diameter of 12 millimeters. It serves to transfer the forces that go from the pusher to the rocker arm. The tube has pressed-in spherical-shaped tips. The lower element rests against the heel of the pusher, the upper one in the adjusting screw. On the tips there are also holes for lubrication. They pass through the cavity of the pipe to the bearing of the valves. The rocker is designed to transfer forces from the rod to the valve. The element is made of steel. Above the bar, the rocker has a short shoulder. Above the valve it is longer. In the short there is a counternut for exposing the thermal gap (applies only to mechanical elements). The bar is located on the individual axis. It is pressed into two bushings of bronze.

Which valve tappet to choose?

As we have already noted, there are mechanical, roller and hydraulic elements. When replacing these parts, the question arises of choosing the best type of pusher. So, let's start in order. Mechanical elements are the simplest and cheaper pushers. Their main drawback is the impossibility of compensating for the gap. As a result, when the engine sets operating temperature, they begin to emit a characteristic noise. All gaps have to be set manually, through the adjusting bolt. As for the hydraulic, they automatically expose all the gaps. These pushers are a small camera, the code includes oil under pressure. Thus, the clearance adjustment is performed by the lubricating system itself. They are inexpensive, and there is no need to adjust them additionally. The only drawback is the "hanging" of the pushers at high speeds. But in this case use roller elements based on them. Hydraulic roller tappets are designed for a long service life. Thanks to them you can significantly increase the capacity of the unit. The dimensions of the valve tappets of this type are identical to the standard ones, so you will not have any difficulties with the replacement. Now this is the most suitable option among all that is on the market.

How to identify a malfunction?

Breakage of this element can be identified by the characteristic sounds. Since the part exposes the necessary clearance, a metallic ring under the valve cover will be heard in the event of a breakdown. As the speed increases, it increases. This means that the body of the element does not receive oil or one of the chambers does not work.

When is this normal?

It is worth noting that the noise from the valve cover when starting the engine is quite normal. If the car costs more than 2 hours, oil from pushers automatically leaves. They need time to get used to it. Running the engine, listen to it. If within 10 seconds noises have disappeared, then the valve pusher has typed the right amount of oil and exposed the gap. If not, it's likely that the element has failed. In view of the low cost, a reasonable decision will be the purchase of new valve tappets. It is recommended to purchase the gears with a set and replace them on each rod.

How to set the thermal gap?

If it's a mechanical pusher, you'll have to do it yourself. Adjustment is carried out on a cold engine. First, open the valve cover. Next, put the fourth cylinder at the top dead center. To do this, you should be aware of the central risk on the front cover of the ICE with the crankshaft pulley. The latter is rotated with a suitable lockscrew for the ratchet. Next, proceed to adjust the eighth and the sixth valve. Using the feeler, we expose the gap between the rocker and the cam by rotating the lock nut. Further we roll the crankshaft by 180 degrees and adjust the seventh and fourth valves. Then - complete rotation and adjustment of the third and the first element. What next? Scroll another one and a half turn and adjust the fifth and the second valve. We tighten the lock nuts and collect the valve cover back. By the way, instead of the crankshaft, you can count the speed of the ignition distributor. It will be easier. But here the setting is set after 90 degrees of rotation. We start the engine and check its noise. It must be lost.

Conclusion

So, we found out what these elements represent. For any symptoms, do not hesitate to replace the pushers. This can reduce the life of the engine, in particular, the parts of the gas distribution mechanism.