Remove the rust from your block. Drain the system and fill it with RUST911. Leave it in for 24 hours. You can drive the car with the RUST911 in it. Drain it. What went in clear will come out black. Repeat two more times and it should drain clear. Flush with water are refill. Add rust inhibitor. You will notice the difference.
https://www.amazon.com/Rust911-16-ga...xpY2s9dHJ1ZQ==