This is a moot point right now, because my original 289 is now at the machine shop so I can rebuild it and put it in the car, but...I'm curious about why this happened...It involves my '65 Mustang... I bought a used 3000ish mile 302 from a local guy who was upgrading. I replaced the Comp 274XE with a cheap Summit 3600 (which worked nicely in my car), and the HV oil pump (that was putting out over 100 psi) with a standard pump. The carb I bought with the engine and was on it for some time was jetted at least 5 sizes too rich on the primaries and was sooting up the plugs. I got it all sorted out, was running 36* total advance by 2500-3000 (engine was under 9:1, I'd say, based on the piston and the combustion chamber). It was running great, until I took it for a 30 minute plus freeway ride and it started knocking. I got home and, long story short, found this on the front two pistons. The rest were only slightly scuffed. What bothers me is why did this thing do this on only the front two (largely), and how could it have run 3000 miles (granted, over a course of 15 years) without doing this? My local machinists are uncertain about what caused it, and on one of the Ford sites I frequent, the opinion is that the pistons were set up too tight and I just happened to be there for the carnage. It appears that the pistons' tops took almost none of the damage (other than from literally rocking in the bore when I disassembled the engine). Once again, I just want to figure this out so nothing similar happens to the 289 if it's something to do with ignition, etc. The plugs on the front two were colored brownish, and the temp gauge never moved, and the engine never got over 200* according to my infrared gun. Thanks for any ideas...
How deep is the scoring on the cylinder walls? Or is that aluminum that has deposited? If the walls are scored, you are looking at foreign material like sand or something. Looking again the rings also appear scored. My vote is for something through the carb. Enough heat to cause this kind of damage, you'd see blackened pistions.
3,000 miles in 15 years is probably a lot of cold startups. Possibly too much fuel washing down the cylinders, particularly if it was one of those cars that had to be pumped several times to start.
The walls are definitely scored...it would have needed to be bored again to clean up, which is why I went with my stock bore 289. All the pistons were scuffed a bit, but the front two were just smoked! I always run an air cleaner, but anything is possible. I didn't find anything in the cylinders. I was curious about the washing down part, because it was running sooooo rich. I just thought it was weird that it was largely the front two.
