Walt Dupont lectures on V8 Oiling

[Bruce Lancaster]

The 10 refers to pressure from oil going into filter and building pressure there because it can't get through fast enough. On a chevy with passenger car post-1968 spin on filter this happens a lot, according to the builders, when oil is cold and at high RPM. Lots of oil bypasses. According to one book I have, the earlier cannister filter had both finer filtering and more flow from its large element, which explains Chevy keeping it as police, truck, and taxi filter for several years after '69.
The various HP books recommend early filter or long truck filter or aftermarket setup with two filters in parallel. Full flow is a misnomer apparently with the standard setup. Racers with one of the greater capacity setups can block the bypass valve because their engine get frequent oil changes and don't have to worry about accumulated dirt.