After measuring the bores Martin uses a micrometer to measure the pistons and the crank journals. The numbers are subtracted to get the piston to wall and the rod and main bearing clearances. Even though you might use a good machine shop, it’s very important to confirm you clearances because mistakes are made and they should be caught now, not on the track!
King Bearings XP series have many built-in features that help with strength and overall bearing performance. Their pMax Black tri-metal structure is built to handle increased load capacity. With their patented SecureBond micro-etch process that improves multi-layer adhesion and integrity, you get a stronger copper intermediate layer and overlay.
The unique 90* U-Groove shape helps with load distribution and durability at high RPM’s without any detriment to oil flow and lubrication.
The GTI-R main bearings also have these extra oil feed holes so you can groove the main saddles and get more oil flow to the rod bearings. We didn’t bother to do this to our G20’s motor because the engine isn’t stressed enough and doesn’t run much boost.
The stock engine didn’t have bearing issues and we figured that just the use of King XP bearings in the wider GTI-R configuration was enough. When you don’t groove the block, the extra oiling holes just are not used. Nothing is harmed or changed.