Valve lifter: description and photo

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:42

In any internal combustion engine there is a valve timing system. It includes a chain or belt drive, gears, intake and exhaust valves. The latter regulate the supply and release of the fuel-air mixture, which burns in the cylinder chamber. It also uses an engine valve tappet. What is this device and what are its features? All this - further in our article.

Characteristic

The valve tappet (including VAZ) is an element designed to transfer forces to the rod from the camshaft. Modern cars use barrel-type mechanisms. They are made of cast iron.

But, since the valve lifters (Ford Focus 2 is no exception) work under load, their lower part is hardened during the casting process. This provides a secure bearing surface for the cam. The barrel-shaped valve lifter has small holes, thanks to whichlubricant circulates. Also, these elements are lighter than mechanical ones. To adjust the thermal gap, a special bolt is provided on it. At the end of the article, we will look at how to do this. Barrel elements are suitable for vehicles with valves located at the top of the block. The lower end of the element is located in the recess, and the valve pusher rod acts on it from above. But regardless of whether it is a hydraulic or a mechanical element, both types work in the cylinder block itself. On old Soviet-made cars, a valve tappet of a different design was installed. They were made of non-hardened steel and placed in a collapsible pusher block. The latter was bolted to the cylinder block. Element cams have curved convex profiles.

Other varieties

Some mechanical valve lifters are equipped with straight profile cams.

Such elements are used together with commercials. The latter rotate on an 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 a flat base. The cost of such a design does not differ from other analogues. However, there is a big drawback here. During operation, the pusher axis wears out significantly. Large shear loads are placed on the element.

About the flat base

The tappet of this type of valve rotates on its guides. What does it give? Thanks tothis reduces the slippage between the pusher and the cam. The wear of the distributor is also reduced. It's more balanced. As for roller-type elements, 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 are made of metal, it tends to expand. Accordingly, the thermal clearances change, especially on the valves.

After all, it is they who let the combustible mixture into the chamber and release the heated exhaust gases outside. To smooth out the resulting noise during operation, modern engines use a hydraulic valve lifter. It compensates for gaps as the unit's operating temperature rises and falls.

How are they made?

There is a plunger in the body of the hydraulic pusher. The latter has two cameras. This is a pressure and supply chamber, which receives lubricant from the engine during operation. This oil then passes through a ball valve to the discharge part. In order to compensate for gaps with high precision, the liquid volume is dosed in the plunger. A spring squeezes it out of the pusher housing. Thus, the thermal gap is restored to normal values. During the opening of the inlet or outlet valve, oil is in the discharge chamber. The ball valve returns part of it back to the supply chamber. When the pusher body moves upward, a certain fluid pressure is created. Oil does not give the plungermove relative to the body. When the valve closes, grease will leak from the plunger side. However, with a new opening, this disadvantage is compensated through the injection chamber. When the engine is started, the elements of the gas distribution mechanism gain operating temperature. The metal expands and the volume of oil in the pressure chamber decreases. Thanks to the coordinated work of the mechanism, the gaps between the valves are compensated. Also, elements such as a rocker arm and a valve stem are involved in the work. Below we will look at what they are.

Rod and rocker

The first element is a metal tube with a diameter of 12 mm.

It serves to transfer the forces that come from the pusher to the rocker. The pipe has pressed-in spherical tips. The lower element rests against the heel of the pusher, the upper element rests against the adjusting screw. Lubrication holes are also provided on the tips. They pass through the cavities of the pipe to the valve bearing. 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 arm. Above the valve it is longer. The short one has a lock nut for setting the thermal gap (only applies to mechanical elements). The bar is located on an individual axis. Two bronze bushings are pressed into it.

Which valve lifter to choose?

As we noted earlier, there are mechanical, roller and hydraulic elements. When replacing these parts, it risesthe question of choosing the best type of pusher. So, let's go in order. Mechanical elements are the simplest and cheapest pushers. Their main drawback is the inability to compensate for the gap. As a result, when the engine reaches operating temperature, they begin to emit a characteristic noise. All gaps have to be set manually, through the adjusting bolt. As for the hydraulic ones, they automatically set all the gaps.

These tappets are a small chamber where pressurized oil enters. Thus, the clearance adjustment is carried out by the lubrication system itself. They are inexpensive, and there is no need to additionally configure them. The only drawback is the "hanging" of the pushers at high speeds. But in this case, roller elements based on them are used. Hydraulic roller tappets are designed for a long service life. Thanks to them, you can significantly increase the power of the unit. The dimensions of this type of valve lifters are identical to the standard ones, so you will not have any difficulties with replacement. Now it is the most suitable option among all that is on the market.

How to identify the problem?

The breakage of this element can be identified by the characteristic sounds. Since the part sets the desired gap, in the event of a breakdown, a metallic ringing will be heard under the valve cover. It intensifies as the rpm increases. This means that no oil enters the element body or one of the chambers does not work.

When is it okay?

It is worth noting that the noise from the valve coverwhen starting the engine is quite normal.

If the car is stopped for more than 2 hours, the oil from the tappets will automatically come out. They need time to get used to it. When starting the engine, listen to it. If the noise disappears within 10 seconds, it means that the valve lifter has drawn the right amount of oil and set the gap. If not, the item is most likely defective. Due to the low cost, a reasonable solution would be to purchase new valve lifters. It is recommended to purchase mechanisms as 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 you need to open the valve cover. Next, set the fourth cylinder to top dead center. To do this, you should be ashamed of the central risk on the front cover of the internal combustion engine with the meta of the crankshaft pulley. the latter is rotated with a suitable open-end wrench for the ratchet. Next, we proceed to adjust the eighth and sixth valves.

Using a feeler gauge, set the gap between the rocker and the cam by turning the locknut. Then we scroll the crankshaft 180 degrees and adjust the seventh and fourth valves. Then - a full turn and adjustment of the third and first element. What's next? We scroll another one and a half turns and adjust the fifth and second valves. Tighten the lock nuts and assemble the valve cover back. By the way, instead of the crankshaft, you can count the turns of the ignition distributor slider. So it will beeasier. But here the setting is set after 90 degrees of rotation. We start the engine and check its noise. She must be gone.

Conclusion

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