here is a pic of our girdle caps getting fitted into a 440 block, obviously the block still needs to be cleaned up and this was just mocked up for the picture. in the #3 main you can see the cast block reinforcement buttress. this cast rib is what allows the stress from the main bearing saddle to be distributed to the skirt of the block. our girdle cap mimics this angle and fits along side it without needing any additional machining or grinding. this serves 2 purposes, first it distributes the load seen by the cap into the girdle and across the entire base of the girdle. and two it creates a pocket where the crank rotates and helps to minimize windage losses.

these buttresses are what needs to be machined away in order to install cross bolted main caps on a 440. someone recently asked my how i would install the cross bolted caps and the answer is i wouldn't but if you fitting them there are two critical areas that need to be fit properly. first is the side to side clearance on the block. this needs to be kept to minimum and an interference fit would be better so the block skirt isn't being pulled in adding stress. the second area is that on the buttress you need to machine a flat, so the area relieved looks like an L in the corner of the L you want there to be a radius. as seen in the pick above there is a radius at the bottom area of where the crossbolt would screw in. ideally the cross bolt cap should touch both parts of the legs of the l shape this will help transfer the load away from the crank centerline. (sorry this is really hard to explain and fairly difficult to machine as well).

i am getting ready to do an install video for bcr caps to post up on youtube and i'll throw in some theory and chalk board time for those really interested. if your not you can fast forward through it.