Any good "high performance" machine shop should be able to O-ring the block for you. It's more commonly done on heads, but the operation is the same. I use a simpler approach on my TR3 (which has mis-cut liner seats). It works well for me, but I don't know how well it would work on a TR7 motor. http://tinyurl.com/2f6lvq5 http://tinyurl.com/3m2tzp3 -- Randall