Christophe wrote:Oh no, I put my veto! A good engine must have a pinion cascade distribution! Rockers show their limits RPM fast enough ...
Objection your honor !
The gable cascade allows a more precise setting of the distribution and does not tire for very high speeds OK .... But it is a sport or competition motorcycle application in general. For a 'normal' car that caps at 5000 rpm (without ever going there for that matter) it is heavier, more complicated, much more expensive without having better performance. So not the best choice. And then the rocker arms, it is not compulsory, the cam can directly attack the tappet against the valve.
But this does not prevent having to do valve clearance... Besides, I do not even know if it is still necessary to do the new cars ...
Indeed, it has already been (20 years or more?) That in the car maintenance books we do not even mention this adjustment, hydraulic overtaking or not.
They found parades, coatings extremely resistant to wear like Stellite that are deposited on the valve stems or the valve seats.
http://www.ms-motor-service.fr/content2 ... =24&upID=2
Seat Armor and Soaking
Exhaust valves, in particular, are subject to high thermal and wear stresses. For this reason,
it is necessary to shield or soak the valve seats. The "Stellite" shielding material has proven to be adequate. Intake valves used on high efficiency engines are mostly induction hardened to prevent deformation and wear of the valve seats.
During operation, the valve stem is subjected to high stresses (hydraulic levers, rocker arms). To prevent wear on the tails, they are soaked. If a valve stem is made of steel that cannot be hardened, then use a satellite shield or weld a small hardened plate.