Spitfire 1500 Stage 4 head, fast road 80 cam, roller rockers, 1.65:1, after 18000 miles since restoration one roller has become detached, one is about to, a crack is evident in third light alloy location. Has anyone experienced this light alloy fracture allowing the rollers to become detached. Would it be possible to retro fit standard rockers, would there be a need to fit shims under the pedestals.New roller Rockers £850!! and they might fail again 18000 is not a great mileage!!