Porsche Cylinder Bore Scoring Explained | RPM Specialist Cars (2024)

FAQs

Which Porsche models suffer from bore scoring? ›

Porsche models from 1997 through 2008 including the 911, 996, and 997 as well as the Boxster, Cayman, 986, and 987 have all experienced the Porsche bore scoring problem.

A lack of cylinder & piston lubrication is the major cause of wear or bore scoring. The minimum grade gasoline for all street production Porsches is 91 octane.

Maintain your fuel injectors – Use a bottle of Driven Injector Defender every other fill-up. We recommend replacing your fuel injectors every 75 thousand miles to eliminate the chance of leaky injectors washing down your cylinders that can lead to bore scoring.

Bore scoring is most common in Porsche 911 vehicles, including 996 and 997 models, fitted with the 3.6 and 3.8 engine. The 3.4 engine fitted to Porsche Cayman S and Boxster S vehicles is also susceptible to bore scoring.

Porsche Bore Scoring

While cylinder bore scoring has been an issue on a relatively small percentage of 996 and 997 models, it isn't a universal problem.

Time magazine featured a cover story about the car, and Motor Trend named the Corvair as the 1960 “Car of the Year.” Americans bought them due to their unique style, and affordable price, well under $3,000. They even earned the nickname, “The Poor Man's Porsche.”

A minor change in piston-to-wall clearance can be considered normal, but changes in the piston-to-wall clearance of more than 0.002-inch should be considered a good excuse for a change.

Repeated overheating caused by lack of lubrication cripples the bearing, which then evolves into IMS bearing failure. The only true way to prevent this is to have your car regularly serviced by expert mechanics and to have an oil change every 2 years.

According to information published about the Eisen IMS Class Action Lawsuit, the single row IMS bearing used in 2000 through 2005 model years is reported to have an 8% failure rate, versus less than 1% with the dual row IMS bearing which has twice the load capacity of the single row bearing used by Porsche.

Not to nitpick, but the difference is that in 2009 model year, Porsche eliminated the IMS bearing completely.

Does Porsche have cylinder deactivation? ›

To maintain efficiency, Porsche introduced cylinder deactivation (which it calls adaptive cylinder control) when the engine isn't working hard.

Many experienced Porsche engine builders and experts on the Flat-6 engine state that the peak power of a Porsche engine is developed around the 20,000 mile mark. This coincides with the principle of what the Porsche engineer was telling me; “Break it in correctly and the engine will last longer and perform better”.

The M96 engine series was officially utilized in the 986 Boxster models from 1997 through 2004 and the 996 Carrera models from 1999 through 2004. It should also be stated that the M96 engine was carried over to the 997-1 Carrera and 987-1 Boxsters in 2005 and even into some 2006 models.

All of these components have a direct affect on compression. For example, as the bore becomes larger, compression increases. If you use heads with a smaller combustion chamber, the compression will increase. Even changing to a thinner head gasket will increase the compression ratio.

Attention is called to the fact that maximum wear usually is found in line with the top ring at the upper limit of its travel. This is attributed to the presence of dirt and to the high temperatures which make lubrication difficult in this region.

The Porsche 911 and Porsche Boxster from model year 1997 to 2005 have a high failure rate of the intermediate shaft bearing also known as an IMS bearing. Its design and construction lead to premature failure of the bearing, which results in catastrophic engine failure.

An electric glass roof that slid under the rear window was one of the innovations of the 911 Targa. However, the real reason that true Porsche enthusiasts still cherish the 993 is the fact that this model, produced from 1993 to 1998, was the last 911 with an air-cooled flat engine.

Not to nitpick, but the difference is that in 2009 model year, Porsche eliminated the IMS bearing completely.

Both the 1983 and 2009 Porsche 911 year models have engine issues. A complaint of broken head bolts was reported in the 1983 Porsche 911, popping up at around 30,000 miles and costing $1,500 to replace.

What is the best Porsche IMS bearing replacement? ›

LN Engineering Duel Row IMS Retrofit

1cc per minute) LN Engineering have sold over 30,000 unit across their range since 2008 and are regarded by some as the first and best replacement option that is available.

The cost of a IMS Retrofit replacement bearing and labour for installation is usually more than $4,000 but can be done in conjunction with the clutch.