That's one of the many reason's I don't mess with chinese covers. That doesn't happen on GM covers. Before you get too in-depth, put the drive gear in the bore and drop a cam sensor down it's bore. If they won't engage, chalk this on up as a lesson. It's pretty common for those bores to be non concentric. If you read the comments in my article and do a search there's many people that put a lot of time in a cover just to learn at the last minute the cam sensor won't drop in.
To save that cover will take some machining ($$) to attempt it. Keep in mind any patch will see close to 100PSI of pressure for the life of the cover. So the last thing you want is to have oil spraying out instead of going to the bearings after you get it all together.
If you spot face that bolt boss and use a copper sealing washer you MIGHT get it fluid tight.
I guess it's depends on how vested you are in that casting. Personally I'd never chance my engine, turbo and cooler when it's already thrown you a flag. But that's just me.
