Sooner or later, any engine becomes a source of trouble: it stalls on the way, does not want to start in the morning, pulls worse, "eating" excess fuel and oil. It is likely that the reason for his capricious behavior is simple: it is enough to clean the carburetor, adjust the ignition and replace the valve stem seals so that everything goes back to normal. But it happens that traditional approaches do not help him, and when measuring compression, it turns out that in one or more cylinders it is below the permissible level - and the issue becomes serious.
Then, first of all, the nature of the malfunction is clarified: wear of the cylinder-piston group, burning of the chamfers of the valves, or wear of the rods and guide bushings. The diagnostic technique is quite simple and is described in all engine repair manuals.
Then they are determined with the repair. Here you just need to take it as a rule: stay away from all sorts of miraculous liquids. The effect is in principle possible, but rarely achieved, the usual result is extra costs and hassle. It is better to immediately focus on a full repair procedure.
Finding a workshop where engines are treated is no longer difficult today, and not only in large cities. But how is the work organized there, what is its quality? Life shows that for all the importance of the experience and qualifications of employees, good results are unattainable without special equipment and equipment, and in this regard, the dispersion of the technical equipment of our stations and mechanics, alas, is large. And if what was said above concerned mainly the motorist-exploiter, then the further presentation is addressed not so much to him as to the mechanic, because we will talk about technology.
In cases where the results of the diagnostic test indicate a malfunction of the valve train, the block head must be removed. The first action after dismantling, disassembly and general inspection is to evaluate the clearances between the valve stems and their guide bushings. If they are higher than the maximum allowable values, the valves are replaced with new ones. But when this half-measure is not enough, the bushings have to be replaced too.
For a small workshop, such an operation presents certain difficulties: cast-iron bushings are pressed into an aluminum housing with an interference fit. In order to avoid microcracks and crushing, the bushings have to be pre-cooled in liquid nitrogen (temperature - 196°C), and heat the body up to 160-170°С (higher may have harmful effects). All this is quite complicated, time-consuming and often simply unreproducible in semi-handicraft conditions. Therefore, in rare workshops, they do not deviate from the prescribed conditions, which directly results in a loss of fit quality and distortion of the geometry of the assembly. It is then corrected by processing "local" valve seats with a drill or cone, and the valves themselves are lapped for a long time and tediously.
But today there is another technique that is highly cost-effective, both in terms of labor intensity and investment, which at the same time guarantees high-quality results. It is achieved by using an original and almost unknown in our practice tool of an American company "Newway" (Neway).
With its help, the restoration of worn guide bushings is carried out on the spot, without pressing out! Special knife-rollers cause plastic deformation of the metal, compensating for wear on the inner surface of the sleeve, at the same time forming a spiral groove in it, which improves the lubrication conditions for the valve stem, and also serves as a kind of labyrinth seal that facilitates the task of valve stem seals.
The kit includes five knives and a set of reamers for finishing the bushing. It is characteristic that all operations with the tool "Newway" are carried out manually and are not connected to electricity supply or other energy from the outside.
Now for the valve seats. With traditional methods of their processing, the guide of the cone or countersink rotates freely in the valve sleeve. cutters "Newway" have a fixed axis, which is tightly fixed already in the restored bushing by a self-aligning expansion collet "pilot". The cutter is put on the axis with a precision clearance of 0.5 microns, which ensures a minimum machining tolerance. cutters "Newway" due to the unique sharpening and shape of the cutting edges, a special microrelief of the type is formed on the surface of the valve seat "comb": valve and seat burn-in is fast and efficient, and there is no need for lapping. Their productivity is high: any chamfer on the valve seat is obtained in 3-4 turns of the tool.
The last stage is the restoration of the working chamfers of the valves themselves. For this operation, the company "Newway" offers a special tool "Gizmatik-2". The valve is fixedly fixed in a special device, which, in turn, is installed in a bench vise. A few rotations of the cutter are enough (axial feed is provided by a microlift), to get a perfect concentric valve surface. Note that on its working surface, as in the processing of the saddle, a special microrelief is also formed.
That, in fact, is all. It remains only to rinse and lubricate all the parts, and you can assemble the head.
And the rubbing? Recall once again: when working with a tool "Newway" there is no need for this tedious, long and tedious operation. After processing a pair "seat valve" the pairing of both parts occurs along a very narrow belt, almost along a line.
This is achieved by small (up to one degree) discrepancy between the angles of processing of the working surfaces of the seat and valve (a so-called interference angle is formed between them). In the first seconds of engine operation, the mating area increases due to the crushing of the surface protrusions of the created microrelief on the chamfers, and then the necessary 100% compaction occurs.
With the cost of a set of equipment about $ 400 (depending on configuration) "Newway" can pay off in the first month of work, and when repairing engines of foreign cars, bring a noticeable income.