Yes you can find more on this issue on pakwheels that the sm and sn rated oil have low zddp therefore cam failure for flat tappets is an issue. As EFI cultus has flat tappets therefore require more zddp. Use sg or sj rated oils, sl maybe used, but not sm or sn. The carby cultus if I am correct it was mentioned somewhere doesn't have flat tappets thus these oils don't damage it as much.
What did your mechanic repair in the head, was there a leak? If yes then it would have been better to go for a kabli one. Heads whose leaks have been repaired leak again as they cannot withstand the optimal temperature of a running car. Make sure your mechanic hasn't removed the thermostat valve, they commonly tend to do so.