Thanks for the info. Do you know someone who can hone rod big ends? The plan is to add 0.0003 to the ID and use coated upper shells and uncoated lowers.
The weak link on these engines are the fasteners that hold them together. This fretting gets worse when the horsepower increases. I do not know how to fix the issue. I manage it by minimizing the runs down the salt to just what I need to do the job and tightening the bolts every off season. The 107 HP the engine makes now looks to be the limit until I figure out a solution to this problem.
I would think that just about any GOOD automotive machine shop could hone them to your spec. The Sunen hone has been a shop staple forever, and it's really not rocket surgery.
On the fretting issue. Do you find that the fasteners are actually loosening, as in the nuts or bolts backing off? Or is it more a matter of stretching fasteners or creeping threads in the case? Do you use torque indicator stripes on the nuts/bolts and if you do are they moving? When I worked on airplanes every torqued bolt had a "torque seal" applied to it by the inspector after he witnessed the torque. This type of stuff.
http://www.mrochemicalsupply.com/product-p/dykem-crosscheck-1oz.htm?gclid=Cj0KCQiAs9zSBRC5ARIsAFMtUXE3OxebyDJZV3wxNDO_cnaslucGAZn9NOPtWKw6E8FngDPA3vxabZsaAopwEALw_wcBA stripe of it laid on the side of the fastener and run down onto the part. It dried hard and made it possible to visually inspect whether the fastener had moved, as it would crack if that did happen.
One often overlooked cause of loss of clamping force it thread creep. It can happen during torquing if the applied torque is more than the base material can stand. It can also happen during operation when heat expansion and engine vibration combine to increase the actual load on the threads, especially if the static torque was already close to the max they could stand. Some designs (later model Harley engines with aluminum cylinders and studs that run from the heads, through the cylinders, and into the cases are one example) cope with this by specifying cold assembly torque specs that are shockingly low, but once everything expands they provide correct clamping force without over stressing the threads in the cases.
One way to check if this is what's happening would be to make a "thread creep gauge". This would be nothing but a short bolt with a line inscribed on the head at one point of the hex, and a hardened washer. Before assembling the engine, lubricate the threads and put the bolt into each hole and torque it to a very low but repeatable number. Make a small scribe line or punch mark (not enough to causing sealing issues) on the case surface to line up with the line on the bolt head. Do this exactly the same way to each hole. Keep the bolt and washer in a safe place. The next time you tear the engine down, perform the same torque sequence with the tool and see if the marks line up. If they don't, The threads are pulling in the case and need attention. Thread inserts can help to hold more torque by spreading the load over a larger surface area of the case, or in some cases actually lowering the assembly torque could be beneficial.
Another thing that can happen is fastener stretch. Test this by documenting the overall length of each bolt or stud prior to assembly, and then checking it when you take the engine apart. On some of the big diesel engine the head bolts have a maximum length that is allowed for re-use. The are known to stretch every time they are used and can only take so many uses before they fail.