Hi guys Under going a restoration project on a 748 and am currently struggling to take off one of the four small triangles bolted to the cylinders. Pic below shows what I'm talking about. Can someone explain what they are for? I'm starting to round off the cap head getting the thing off and if I knew what purpose they serve I'd know whether it's worth my while to continue trying (seeing as the engine is already out it'll be my best chance to do these things now rather than later) or if they are best left alone. It's only the one bolt that's seized in, but I reckon I'm going to have to drill it out or weld a nut to to free it up. Any advice would be greatly appreciated
They are blanking plates that lead into galleries. They can be very difficult to get off and sometimes the corners can break off the triangles especially if you try and use an impact driver. It's not necessary to remove them at all unless you are say converting to all stainless bolts on the engine. I always replace my countersunk bolts with stainless ones and if one does round off I try and drive them out using a sharp punch on the head of the bolt and that usually works. I have changed a number of these and only had one "triangle" break and that was because the alloy had mostly become very brittle. They are not that cheap to replace and there is an O ring used to seal the plate in position and stop leaks.
As said, blanking plates because the front and rear cylinders are identical and interchangeable but they need the coolant unions and belt pulleys swapping over so have both fittings on both sides. Be careful tightening them as I've seen one break as the countersink of the screw pushed/expanded into it, they are quite fragile and as Red998 says probably not cheap...
