Hi
The competition liner, besides the quality of materials, which sometimes does not differ much from the standart, has in comparison 3 essential characteristics.
The first, is the quality of the material:
It is very important that the liners, be made from a massive iron block and not perforated in which pores can take place that are not appraised at first because they are in the inside of the material and that during the work of the engine they can appear producing the breakage, this massive iron block guarantees the pore absence with the consequent security and resistance of the set.
The second, is the grating of the liner:
The grating of the liner usually come normally expressed as a measure called “Ra code” and this code depends your depth.
As more high is the code Ra, deeper drawing and deeper so that, to get on and off the piston more oil is on the liner, reducing the risk of break and lower index of friction.
The third, is the fit between piston and liner:
As more slack between the liner and the piston, lower is the friction.
This clearly produces a little oil consumption, but avoids more the risk of breakage and increase the torque/power by decrease the maximum friction between them.
The competition piston is clearly very different to the standart, in the materials of construction and design and weight.
Normally forged or ceramic, in these pistons, the rings are more thin that standart or sometimes only two rings instead of the usual three, removing the oil ring.
The competiton pistons have the diameter of the head and tail that usually is smaller, so that the to avoid possible friction on the liner produced dilatation by the piston and the liner, have pockets for larger valves and profound and less weight.
The dilations are usually higher in the competition engines, produced by the octane of fuel, the ratio compression and linear velocity piston.
Besides the oil hole have increased in number in the oil ring.
One thing that confuses people is always the oil ring, very bad call by the people, because this ring not lubricate anything, quite the contrary, their mission is to remove the oil that is deposited on the liner in its wake and and it directs towards the existing holes in the piston to fall on the crank, con rod, sump and pin piston.
The material is also different from the piston rings, which is usually more resistant to heat and fatigue effort.
Besides a slack in the way we do an engine for competition, eliminates much of the friction, and may use the engine in competition almost since birth.
These data must be taken very present at the time of making a block, as their use determines the holguras and “RA codes” of the liners.
Also the height of the liner is important, which should be on 0.125 mm about the top block and tighten of the liner on the block is very important to avoid possible movements of this, it should be completely trapped by the block.
The liners must enter the block with heat, warming up the block to dilate and when cooled, the liner have pressure and not enter with the hand, as in the block standart.
To make a good block with the liners, is also necessary to have a torque plate.
Once the liner is in the block and cold, is to make inside diameter completely focused and the grating in the �RA code� most appropriate for use of the engine.
The “RA code” in the standart liners is between 0.35 and .050.
Finally cut the liner to the desired height.
Regards
Vicente