Holden Commodore Problems

Your friend is basically correct, the Gen III V8 is calibrated to run on ULP, and running it on PULP would produce only a small improvement. Overfilling some engines with oil can lead to damage, but in the case of the Gen III it seems there is no danger. It should only be done as an added precaution on engines that do consume oil, and I wouldn't follow the practice if your engine isn't devouring oil. You sound like someone who keeps a close check on the oil level, so I would recommend you fill it to the correct mark and keep monitoring the level. The number of problem engines is quite small, Holden says it is less than 2 per cent of V8s, so I wouldn't be concerned unless your engine is actually using oil. The fix implemented by Holden from the start of VY has done the trick, according to engine rebuilders.

I would definitely dispute the need to do anything in this case. You should be able to detect a blocked injector. The engine should run a little rougher at idle and under load, but if it's not, I would suggest there is nothing wrong. The fuel consumption numbers you quote are in line with what I would expect from a VX II Commodore V6.

I have never tested any of these devices so I can't offer an opinion other than that I am sceptical of claims made for them. Others who have tried them might be able to provide information. If you have, send your comments to grah.smith@bigpond.com

We checked with Peter Schweighofer of Swift Automotive in Melbourne who recommends the HM headers and exhaust system. If your car is an auto, he also recommends you have the shift pattern altered to make it sharper.

Sounds like you've got a nice FE there, Jason. I don't have any experience with devices like the fuel catalyst, but am sceptical of the claims made by their makers. You can modify your engine to run on unleaded fuel and that's what I would recommend. Any reputable engine builder can carry out the modifications, which involves fitting hardened valve seats to the cylinder head, and hardened valves. All that's doing is reducing the valve-seat wear which increases without the presence of lead, which acts like a lubricant on the valves and valve seats. It's also necessary to retard the spark on some engines so they run on ULP, although they might run quite happily on the higher octane PULP. I'd expect your engine, with its modest compression ratio of 6.8 to 1, to run quite happily on 91 octane ULP, but if it pings try PULP, or have the distributor modified.

Like you, Mick, I can't explain why the acceleration figures for the supercharged Commodore should be shown as similar to the non-blown car. It doesn't stand to reason. The figures shown on Holden's website are not Holden's own performance numbers. They are taken from a comparison test done by other people. Holden doesn't publish official performance data. The numbers I have suggest that the correct 0-100km/h acceleration number for the normal V6 is about 9.2 sec and the supercharged car gets the job done in about 7.5 sec.

I've put your concerns to Shell's technical people and requested an answer. Hope to be able to report back to you soon.

Thanks Matt. I'm sure Virginia will be keen to check it out.

You really need to have it checked by a mechanic. It could be oil being sucked into the engine past the valve stem seals and burnt, or it could be running very rich. If it is the latter it could be because of a malfunctioning oxygen sensors in the exhaust or the engine temperature sensor, telling the computer the engine is running lean or it's not up to working temperature, and forcing the computer to pour more fuel in.

You've done just about everything possible and seemingly without finding the cause of the problem. The Commodore of that era is prone to driveshaft vibrations. I would suggest you have the driveshaft angles checked as that is often a source of problems like you describe. It is almost certainly a drive-line problem.