Posting for friend with 496 with the 525 Raylar kit. No issues until early last year started loosing a little coolant. End of season finally found mechanic willing to check it out and diagnose was a cracked head. Heads replaced, winterized and then upon spring start up, it was hydro - locked. Took back to mechanic and now thinks the block is cracked, coolant into #5 and #7. Friend already has $4300 into heads and asking opinions which direction to go now? I was wondering if issue could be in the exhaust risers? Personally not convinced cracked head or block, and ideas?