My 100 has a very early Le Mans conversion and has the higher 8.1:1 compression ratio pistons and cam fitted
Just putting the head back on after replacing the valves and springs and my standard 100 service manual quotes 65-70lbft torque for the head nuts. Does anyone know if there is a higher torque recommended for the 100M compression ratio?
Mike’s answer is of course correct - go beyond OEM limits and there is a risk it will go wrong. I saw a narrative elsewhere that someone had used 80 Lbs ft after his 100M head gasket had blown twice. So it’s a choice really: risk some stretch at 80 or risk a blown gasket at 70lbft.
My torque wrench comes with a table that suggests that a 5/8 UNF bolt of the basic quality steel has a recommended max of 81.9lb ft. Higher grades are good up to 167!