Yeah, I probably wouldn't have believed it either if I hadn't seen it with my own eyes but it's the reason I eventually had to pull the motor and have it rebuilt. In fact, it's the reason the original owner sold the car to me in the first place, the engine was overheating. I remember the guys at NAPA, they recognized exactly what the blockage was when I took the engine and heads to them to be chemically dipped. The issue I had was 35 years ago, so maybe today's stop leak works better, and all of that blocking material goes right to your problem area and nowhere else in the engine, who knows. However, I would still suggest trying to fix a leak the right way instead of looking for a 5 minute miracle solution with an $8 bottle of stop leak.
