Cosworth Vega is a neat engine in a disposable body. I went through a couple of them. Rust got one, a drunk old lady got the other. Both '75s. I had one spin a rod bearing and got to take it down to the bare block. The factory had forgotten to drill a hole that let oil go from the filter outlet to the main gallery. All of my oil was going through a bypass valve for a clogged filter.
No wonder the filter always looked so clean after changing it. It's a miracle that it lasted 30,000 miles. Amazing how much better the pressure was after I drilled the hole. That lasted another 65,000 until the body fell apart. Sold it to a guy for the engine & trans.
Anyway, I had all the factory manuals for the beasties. The material in the aluminum block is definitley silicon, not any form of silica or silicon dioxide. The recommended hone after re-boring was abrasive on felt pads, but that was in 1975. The neatest application of that technology IMHO was the 427 "Chevy" race engines in the McLaren Can-Am cars of the late Bruce & Denny show. They make a nice rumble.
I autocrossed the CosVeg a bit. Took it to a Corvette club autocross at a go kart track by mistake but they let me run anyway. Sympathy for the "little four cylinder", I guess. I came in second overall
but no trophy because it wasn't a Corvette. Buncha waxers & polishers.