ACL H VS HX
Bearings that have an HX in the item number give 0.025mm. more space for oil film.
See how to disassemble the rest of the block in the repair manual. The following tolerances must be checked as a minimum, piston rings, cylinder, connecting rod bearings, and crankshaft bearings. The procedure is described in the repair manual. The measurement of the bearings requires the special measurement tool (a micrometer screw)
The oil pressure tells you how your engine's bearing feels and how your oil pump feels. It is very important that the test is performed on a hot engine (8-10 km), as the pistons expand with the heat. Remove your oil lamp gauge from the engine block and insert a manometer into the hole instead. The pressure of the oil pump depends on the speed. The oil pressure at idle is very different from engine to engine, you can find the pressure for your engine in the repair manual. The high oil pressure is determined by the pump overpressure valve, and this is not usually where the problems are seen.
If the oil pressure is too low at idle, it may be because your bearings are so worn that the oil runs straight through the bearings (too much air between shaft and bearing). It could also be your oil pump that is defective or worn. If there are problems with the oil pressure at low revs, check the engine carefully (it may sing on the last verse). If the oil pressure is too high at high revs approx. above 2,000 rpm, it may be your overpressure valve in the oil pump that is defective or clogged. If you need to tune the engine a lot, it may be a good idea to install a better oil pump and at least an oil cooler. You can get pumps and coolers in the tuning shops.
Race bearings are often used when the engine is to be high-performance. Bearings are often heavily loaded and therefore it is recommended to use a racing bearing that has a hard surface and is not pressed flat at high load or charging pressure. It is recommended to drive with bearings that have the same tolerance as original bearings. If you need to build a very special motor that either has to have lower resistance at the bearings at high revs or if you need to drive with a very high charging pressure, you are welcome to contact us.