Australian Car Repair Issues? Ask an Auto Mechanic for Answers ASAP
LS engines are prone to roller lifter and cam lobe failure.
I would get the car inspected by a good Holden tech, or LS tuning shop, that does cam/lifter changes.
Cylinder heads have to come off to replace lifters.
If the engine is stock, then you probably have the start of intermittent roller lifter "tick", that can be saved.
Unfortunately, it is engine out, heads off type job.
My recommendation is to replace all the factory gear with aftermarket parts: cam, lifters, guides, pushrods, rocker arms, retainers and springs.
The factory springs break, the factory roller lifter wheels gall on the cam lobes, from seizing up on their axles.
They have enough lifter preload from factory.
Do you need any further assistance?
I have built many V8 engines including LS1 onwards.
A crate engine is also sometimes cheaper in the long run.