Is there any way of doing it ?
You know ... like from the North Atlantic - washed ashore. [humour off/] From bits of old gasket stuck on the block, carbon round the bores and associated detritus.
To stop stuff getting down waterways use masking tape. you can do the same with bolt holes, but its easier to put the bolts back in. for scraping carbon off the piston crowns wipe a lick of grease round the edge of the piston (at TDC) then scrape into the grease. when finished with that piston, wipe off then lower it a bit and wipe the bore. Mike