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M96 M97 1997-2008 Boxster Cayman 911

M96 M97 1997-2008 Boxster Cayman 911

When planning to rebuild the flat 6 Porsche M96 engine or M97 engine in your Boxster, Cayman, or 911 vehicle, there are many considerations when evaluating your options to correct for bore scoring, intermix, cylinder cracking, d-chunk , and even slipped sleeve failures.
 

Why use LN Engineering for M96/M97 engine sleeving?

With thousands of engines fitted with Nickies over the span of more than a decade, no one has more experience than LN Engineering when it comes to solving cylinder issues associated with Lokasil engine blocks, especially with displacement increases up to 4.0. No one has been sleeving big-bore M96 and M97 engines longer than LN Engineering anywhere in the world.
 

How much does it cost to rebuild a Boxster, Cayman, or 911 engine?

Although you may find Porsche engine rebuilds advertised for under $10,000, it's a guarantee that the cylinders have not been properly reconditioned and that what they are quoting is likely no more than fresh gaskets, bearings, seals, rings, and a valve job. However, with an M96 or M97 engine, there is much more to a proper rebuild. Ask for a parts list of what is reused versus replaced and you'll quickly see the difference between their $10k repair and a proper rebuild like what is offered by RND Engines and why there is a $10k difference.

The cost really isn't much different than rebuilding an aircooled 911 engine. As a rule of thumb, a basic M96/M97 rebuild with Nickies is going to run you about $15-20k, more for engines with ported heads and other internal upgrades like forged connecting rods or bolt-ons like an IPD Plenum and GT3 throttle body. There are lots of ancillary components that should or need to be replaced like fuel injectors, MAF and o2 sensors, dual mass flywheel, clutch, expansion tank, and other items, especially on a car that is 15-20 years old. Cutting corners anywhere in the process can end up costing you more in the long run. Many don't have enough money to do the job right the first time, but have more than enough to do it over again.

And yes, it is possible to spend as much on an engine as what the car might be worth. The question you have to ask yourself is what is it going to cost you if you go out and buy a new Porsche. Will you get as much enjoyment out of a new Porsche than building up your current engine and keeping your car? Just ask those early adopters over a decade ago that had us punch their 3.2 Boxster S and 3.4 996 engines to 3.8 liters and 3.6 996 engines to 4.0 liters and owners of the thousands of aircooled and watercooled Porsche vehicles who have trusted our Nickies cylinders and sleeves.
 

Why can't you just re-ring the pistons and re-use the block as-is?

You get what you pay for. Re-ringing your isn't an option for most rebuilds, however most engine builders re-ring engines after only doing a visual inspection of cylinder bores for obvious cracks or scoring without measuring the cylinders for ovality, taper, and proper surface finish. Most shops don't own a profilometer to verify Ra, RpK, RvK, or Rk, let alone precision measurement devices, to be able to inspect the engine block. In fact, most every used engine we have ever inspected has more than the allowable 0.08mm (.0032") ovality and taper specified by Porsche. Having had the change to inspect numerous new engine blocks, we know they are near perfectly round with less than 0.02mm (.0008") ovality or taper.

It is a guarantee if the engine has not been reconditioned either by sleeving or direct plating, the bores are out of spec on even a "fresh" rebuild. If the bores do happen to be in spec, there is also the issue of other known modes of failure associated with Lokasil and Alusil engine blocks including, but not limited to d-chunk, cracking, and scoring failures. Nickies cylinders with NSC (nickel silicon carbide) plating, similar to Nikasil, address all known cylinder weaknesses that direct plating of blocks cannot address.
 

What is bore scoring and how do scored 996 and 997 cylinders affect M96 and M97 Porsche engines?

The Boxster, Cayman, and 911 from 1997 through 2008 use the Lokasil hypereutectic engine block casting technology, which is similar to Alusil, both developed by Kolbenschmidt. Alusil is has been used in many Porsche models including the Porsche 944, 928, and 968. This also includes the Cayenne V8, Panamera V6 and V8, and most recently, 2009 and later models with the 9A1 (MA1) engine found in Boxster, Cayman, and 911 vehicles.

The silicon particles in the Alusil and Lokasil cylinder bores are exposed through a mechanical or chemical process that removes the surrounding aluminum. The piston/ring/cylinder system is supported by these exposed silicon particles and the oil film on the bores. If there isn't sufficient exposed silicon particles or oil film, the cylinder system can no longer function normally.

To prevent aluminum to aluminum contact of the pistons and the cylinder bores, the pistons are iron clad. When the iron coating fails, adhesive wear (scoring) of the cylinder bores can occur. Cylinder bore scoring isn't limited to just Lokasil engines - it can occur with Alusil or any other hypereutectic cylinder technologies.

Symptoms of bore scoring on affected models includes piston slap and excessive oil consumption. Engines with scored bores are often misdiagnosed as having noisy lifters. Another indicator besides piston slap is having one tail pipe sootier than the other, with the driver's side tail pipe on a 996 or 997 with scored cylinder bores getting sooty first. Boxster S and Cayman S models with the 3.4 engine will have the passenger side tail pipe get sooty first. Even before there is any noticeable oil consumption, piston slap caused by the increased piston to cylinder clearance and sooty tail pipes can occur. When oil consumption becomes excessive, spark plugs can become oil fouled causing misfires on cylinders 4,5, and 6. Vehicles with excessive oil consumption will likely also have significant oil film on the rear bumper cover.
 

How can I prevent bore scoring?

Besides the failure of the iron clad coating on the piston skirts and fracturing of silicon particles on the cylinder bores, both of which will result in bore scoring, we have determined that bad fuel injectors as well as vacuum leaks can lead to cylinder bores being washed down from un-atomized or excess fuel. Fuel is not a lubricant, especially ethanol enriched fuels that have reduced lubricity compared to ethanol-free unleaded fuels. Dirty injectors can result in poor fuel atomization - un-atomized fuel does not burn and will up washing cylinder bores down and lead to high fuel dilution of your engine oil. Leaking injectors will bleed down, dumping raw fuel into the bores, washing away all lubricant at start up, increasing cylinder wear. Likewise, vacuum leaks will make an engine run rich, again washing the cylinder bores down. Smoke testing your engine for vacuum leaks and monitoring fuel trim values are two easy steps you can take to make sure you lessen the chance of bore scoring in your Porsche engine.

If you want to learn more about how and why bore scoring occurs, check out our free download on Bore Scoring in AlSi Cylinder Systems.
 

How common is bore scoring?

When we started sleeving M96 engine blocks with Nickies in 2008, most of the cylinder failures we experienced were not bore scoring related, but rather cracked cylinders, d-chunk, and slipped sleeve. But as these cars have gotten older, bore scoring is the number one failure we see, specifically 996 and 997 models. 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. The 2.5, 2.7, and 3.2 Boxster and Boxster S engines as well as the 2.7 engine fitted to base Boxster engines are not known to suffer from scored cylinder bores.
 

How can I determine if I have scored bores?

Besides the obvious symptoms of piston slap and oil consumption, borescoping the cylinder bores and performing used oil analysis can help identify early cases of bore scoring before there are any symptoms. When bore scoping the engine, it is important to check cylinders 4, 5, and 6 as bank two always scores first. The engine needs to be bore scoped from the sump with the piston at top dead center, since scoring always starts at the bottom of the cylinder. Checking for scored bores with the spark plug removed and the piston at bottom dead center isn't always effective in identifying early cases of scored cylinders. Besides bore scoping, used oil analysis can identify increased aluminum and silicon content which are good indicators of cylinder bore wear.
 

What is a D-chunk failure and can my Boxster, Cayman, or 911 engine suffer from cracked cylinders?

Although D-chunks failures occur most often on 99-01 3.4 996 engines, any M96 or M97 engine can have cracked cylinders. Like with bore scoring, 2.5 and 2.7 base Boxster and Cayman models do not suffer from cracked cylinder bores or d-chunk failures. 996 and 997 bore scoring is a much more common mode of failure than cracked cylinders on 3.6 and 3.8 models.
 

What is a slipped sleeve failure?

In the first few Boxster and 996 production years, the company that cast the engine blocks had some supply issues, requiring some engine blocks to be sleeved by the factory. These blocks were bored out to accept a metal matrix composite sleeve. Sleeves were located and retained by a small lip at the surface closest to the cylinder head. Over time, the sleeve can come loose and the sleeve can fracture at the lip. When this occurs, the sleeve is dragged towards the crankshaft and if the piston rings get caught on the fractured lip, the top of the piston can be ripped off, resulting in a catastrophic engine failure.
 

Can direct plating the M96/M97 engine block with Nikasil plating be used to correct for cylinder bore scoring?

With aircooled Porsche engines, the factory Nikasil plated cylinders can be stripped and replated when bores are beyond their wear limit. Likewise, Alusil cylinders used on 2.7 and 3.0 911 engines can be repaired using Nikasil plating as well. Technically the M96/M97 engine can be reconditioned with Nikasil plating, however there are limits to what the Nikasil plating process can correct. Bores that are heavily scored have to be bored out then plated back to size, however there are limits to how thick the Nikasil plating can be applied. Normally Nikasil is applied .004-.006" thick per side. The Nikasil plating also won't prevent future cylinder issues from cracking or d-chunk failures. Also, the longevity of the repair is only as good as the parent metal that supports the Nikasil bores. Knowing the engine blocks can and do go out of round, suffering from ovality and taper issues even with low mileage, sleeving of these engine blocks is the only proper solution to correct for scored cylinder bores, cracking, and d-chunk failures.
 

Why don't conventional cylinder repairs work on M96 engine blocks?

In a normal engine, manufacturers supply oversized pistons and provide a procedure to overbore and hone blocks when they need to be reconditioned. With a hypereutectic engine block, further steps are required to do the required exposure process for the silicon particles and the pistons used have to have the required iron coating on them, meaning aftermarket pistons cannot be used. In the case of the M96/M97 engine and all other Porsche engines using Alusil engine blocks, oversized pistons are not available and procedures have not been provided by the manufacturer. This requires that blocks are replaced, sleeved, or direct plated to correct for cylinder wear or failures.

We have seen many engine blocks come to us over the years with a single sleeves fitted after a scored bore, d-chunk, or cracked cylinder occurred, but only to have another cylinder fail only months later. Likewise, direct plating of the bores can correct for ovality and taper, however it doesn't prevent a future cracked cylinder failure. Sleeving is the only way to ensure you do not have a future cracked cylinder.

However, not all sleeves are created the same. There are two types of sleeving - dry and wet. Dry is where a thin wall sleeve is pressed into the original cylinder after it has been slightly bored out to accept the repair sleeve, with some having a lip at the top and some being a straight sleeve. This is similar to what was done by Porsche on the blocks that suffer slipped sleeves. A wet sleeve is one where the sleeve sees contact with engine coolant and requires the original cast in cylinder sleeve to be machined out of the block. Due to dissimilar alloys and differences in expansion rates between the sleeve and aluminum block, both wet and dry steel or cast iron sleeves have to be installed with an interference fit. Too much interference and the block can crack or if too little interference fit is used, sleeves can move around, resulting in head gasket failures and intermix. Once the block's parent metal is cracked, it can't be cost effectively or safely repaired and must be replaced.

Another issue many do not take into consideration is that the M96/M97 engine, as all other hypereutectic engines, are all-aluminum. These engines were never designed to be fitted with steel sleeves where other aluminum blocks used by import and domestic manufacturers came with steel sleeves fitted from the factory. As you can see below, an engine with steel sleeves requires larger water jackets and increased cooling system volumes to make up for the loss of thermal conductivity. Aluminum has three to four times (3-4X) the thermal conductivity of cast iron. Add in an increase in displacement, and a steel sleeved M96 engine is already compromised, compared to one that is all aluminum. Putting a steel or cast iron sleeve into an aluminum engine block is a step in the wrong direction, using dated technology.

Nikasil has been used for decades because of its low friction and low wear properties compared to cast iron. Even in an engine with cast iron cylinders, a simple change of Nikasil plating the bores can result in a significant enough reduction in friction that many will see 8-10 horsepower increase alone. This also translates into lower oil temperatures as the friction between the piston rings and the bores are one of the largest sources of friction within an internal combustion engine.

Lastly, just as in an aircooled engine the use of aluminum cylinders allowed Porsche to increase the output of the engine without thermal overloading, the same goes with a watercooled engine. Case in point, when Porsche introduced the 944, a first for Porsche using an all-aluminum Alusil engine block, they were able to increase the output of the engine compared to the 924's cast iron block, all without sacrificing reliability.


Steel sleeves, although inexpensive, have limitations including increased friction, reduced cooling, and shorter service life than our NSC-plated Nickies featuring all-aluminum construction. Why use anything less than the best?



BESIDES NICKIES™, LN ENGINEERING OFFERS AN EXTENSIVE LINE OF PARTS AND UPGRADES TO ADDRESS MOST OF THE KNOWN ENGINE ISSUES DURING REBUILD. DOWNLOAD OUR M96/M97 REBUILD GUIDE AND NICKIES + IMS PROGRAM BROCHURES TO LEARN MORE:


 

Download Rebuild Guide Brochure Nickies + IMS Program Brochure / presentation

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