Holden Commodore Engine Problems

The increase in consumption you report is certainly higher than would be expected, but that could be because you were towing. Try it again in normal day-to-day driving and see what you get. The expected increase in consumption is about three per cent and that should be offset by the lower price of E10.

On your figures it’s getting 19 L/100 km whereas it should be getting around 11 L/100 km. That says there’s something very wrong, and the petrol smell suggests it could be running very rich. It could be a problem with the oxygen sensor. Have it checked out.

While oil usage is something to watch your car isn’t using a lot of oil and the trade advice is that the 6.0-litre V8 doesn’t generally have a problem with oil consumption. I would check the oil regularly and if the consumption increases then take it back to Holden for investigation. As an aside most mechanics believe the factory specified service intervals are too long and strongly recommend changing oil more frequently, at 5000 km or so intervals.

It sounds like the engine is overheating and you should have it checked to determine the cause. If it is overheating be careful about driving it as you could de even more damage. Any mechanic could check it for you, it's not necessary to take it back to the place you bought it, unless of course you have some form of warranty and want them to cover the cost of the repair. You could trade it in if that's what you want, but dealers might be reluctant to accept it if it has a problem. The best course of action would be to find out what's causing the problem and have it repaired.

It doesn’t sound like there’s anything wrong, the ‘smoke’ is pretty normal for most cars during the warm-up phase.

I would put my money on the Crank Angle Sensor, even though you are willing to rule it out. It does sound electrical and the CAS is often the culprit in these deals.

The presence of exhaust gases in the coolant suggests it's either a head gasket leak or perhaps a cracked head.

It does sound like a loose timing chain as the Holden dealer has suggested. We've had another report of a broken timing chain on an Alloytec engine and the result in that case was a badly damaged engine, so I would act quickly and have the chain checked and replaced if worn or loose.

The VH was built in the days before we had unleaded fuel. In standard form the 202 cubic inch six had a compression ratio of 8.8:1, so it would have been running on the Super fuel of the day. Fitting an aftermarket head is probably going to increase the compression ratio, and you’ve got a sports cam, so I would tend to run it on 98-octane fuel, and it will need an additive like Flashlube of Valve Saver if you don’t have hardened valves and valve seats. If you don’t have those I would recommend you fit them in the rebuild, that way you could use unleaded fuel without an additive.

The fact that it’s running roughly once it’s warmed up suggests you have a problem with either the head gasket or the head, even though there’s apparently no oil in the coolant. Try and identify which cylinder, or cylinders, are misfiring and remove that head to check it.