To the cylinder head This is a true RBC cylinder head While using the misplaced motion castings set up ready to swap more than rockers and cams from my destroyed RBB. The engine also came with the RBC VTC gear. So all and all it might have been lots improved https://jdm-engine-4age-blacktop01862.bcbloggers.com/31919188/jdm-nissan-skyline-rb26-motor-for-sale-used-rb26-engine-things-to-know-before-you-buy