What Porsche Owners Need to Know About the M97 IMS Bearing (2006–2008)

Jake Raby of Flat 6 Innovations, the inventor of the IMS Solution, has spent decades educating Porsche owners on the nuances of intermediate shaft (IMS) bearing failures. In a recent RenVision video, Jake shifts the spotlight to the often misunderstood M97 6305 large single row IMS bearing, used in 2006–2008 Porsche Cayman, Boxster, and 911 models.

This article highlights key takeaways from Jake’s video and explains what every Porsche owner should know if their vehicle is equipped with the M97 bearing.

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What Is the M97 IMS Bearing?

The M97 IMS bearing is a large single-row 6305 bearing introduced in mid-2005 and fitted to all 2006–2008 Porsche 987 (Boxster/Cayman) and 997 (911) models with the M96/97 engine family. It succeeded earlier dual-row and 6204 single-row IMS bearings, which were more prone to failure.

The larger M97 bearing has proven to be highly reliable, with Jake Raby personally having seen only three failures since 2006.

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Why the M97 Bearing Can’t Be Retrofitted (Under Normal Circumstances)

A crucial point often misunderstood: The M97 bearing cannot be removed without full engine disassembly. Unlike earlier IMS bearings that could be accessed through the crankcase's rear service port, the 6305 bearing is physically too large to pass through this port.

Modifying the crankcase to access the M97 bearing is strongly discouraged due to the risk of damaging structural integrity.

🔧 If the engine is apart, the M97 bearing can and should be replaced—preferably with the IMS Solution, a permanent fix developed by Jake Raby and sold by LN Engineering.

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What to Do If Your Porsche Has the M97 Bearing

Jake's advice is straightforward:

• If your engine is together and running well, do not retrofit the M97 bearing.

• If your engine is apart, it makes sense to upgrade the bearing while you’re in there.

LN Engineering offers a ceramic hybrid bearing replacement or the IMS Solution, which replaces the ball bearing entirely with a plain bearing and provides future serviceability via a bushing adapter.

🛠️ Learn more about replacement options here:
👉 M97 IMS Bearing Replacement Guide

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What About 2005 Model Year Vehicles?

The 2005 model year is a gray area. Some engines from 2005 were fitted with the older, failure-prone 6204 single-row bearing, while others received the newer M97 6305 bearing. Unfortunately, VINs and engine numbers cannot reliably tell you which you have.

Jake recommends a visual inspection of the IMS flange bolt:

• 13mm nut = early single row (6204) bearing

• 22mm nut = M97 large bearing (6305)

If you discover a 13mm nut during a clutch job or other gearbox-out service, stop and retrofit the IMS bearing immediately.

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What About Factory Replacement Engines?

Even early Boxsters and 996s (1997–2004) may have M97 bearings if they received factory replacement engines after 2005. Porsche retroactively used the 6305 bearing in replacement engines, regardless of model year.

Some clues:

• Later replacement engines often use inverted Torx fasteners instead of hex head bolts.

• Engine serial numbers marked “M96” may still contain M97 internals.

• Visual inspection remains the only reliable method to confirm.

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Should You Still Be Worried About the M97 Bearing?

While Jake Raby dislikes ball bearings inside engines as a matter of principle, he acknowledges that the M97 IMS bearing is robust and rarely fails. That said, high-mileage or heavily tracked cars may be more vulnerable.

Best practices for owners:

• Change your oil every 6 months or 5,000 miles, whichever comes first.

• Use a quality oil and monitor for early warning signs like unusual noises.

• If the engine ever comes apart, replace the IMS bearing proactively.

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Final Thoughts

Jake Raby’s RenVision video clears up much of the confusion surrounding the M97 IMS bearing. His message is clear: Don't panic if your Porsche has the M97 bearing, but be informed and plan ahead.

If your car is from 2006–2008, rest easier knowing the bearing is strong. If it’s a 2005 model or earlier with a replacement engine, take steps to visually confirm which bearing is present—and only trust direct inspection, not VIN or lawsuit eligibility data.

🔗 Related reading:

• Definitive Guide to M97 IMS Bearings (LN Engineering)

• M96/M97 IMS Bearing Failures and Solutions (Part 1)

• M96/M97 IMS Bearing Failures and Solutions (Part 2)

Replacing Head Studs in Air-Cooled Porsche Engines: A Step-by-Step Guide

Replacing the head studs is a crucial part of rebuilding any air-cooled Porsche engine. This is especially true if your engine is equipped with Dilavar studs, which are known for their tendency to break. In our latest YouTube video, we demonstrate how to replace and install head studs properly, ensuring a strong and reliable engine build. Here's a detailed guide to accompany the video.

Why Replace Head Studs?

Head studs play a critical role in maintaining the structural integrity of your engine. Over time, factory studs, especially Dilavar ones, can fail, leading to serious engine issues. Upgrading to high-performance head studs, such as ARP 204-4206, ensures durability and eliminates the need for future replacements. These studs are designed to be the last ones you’ll ever need.

Porsche ARP Head Studs 204-4206

Step 1: Preparation

Before installing new head studs, some essential preparation work is required:

Running a tap or thread chase to ensure threads are good in the block.

1. For Aluminum Cases:

• Run a thread chaser through the head stud bosses to clean and prepare the threads.
• If the studs don’t thread in far enough, use a forming tap to correct the threads.

2. For Magnesium Cases:

   • Install steel case savers to strengthen the thread bosses. This step is critical for ensuring the studs remain secure over time.

3. Timing:

• Perform these operations before starting engine assembly.

Step 2: Installing the Head Studs

1. Threading the Studs:

• Studs should thread into the case by hand if the threads are clean and prepared.
• If manual threading isn’t possible, use a double-nut method or a stud installation tool to fit the studs.
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  Threading the head studs into the engine case.

2. Using Loctite:

• Apply Loctite to the threads if recommended for your application. This helps secure the studs to the case.
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  Proper application of loctite to cylinder head studs

3. Avoid Bottoming Out:

• Take care not to overtighten or bottom out the studs during installation.

Step 3: Fitting the Cylinder Heads

Fitting the cylinder heads

1. Preliminary Assembly:

   • Once the Porsche cylinder and piston assemblies and heads are fitted, install the nuts and washers onto the studs.

2. Lubrication:

   • Lubricate the stud threads, nuts, and washers with the ARP assembly lube provided with the kit.

3. Hand Tighten:

• For initial assembly, tighten the nuts by hand to secure the heads in place temporarily.

Step 4: Torquing the Head Studs

Proper torque sequence for Porsche cylinder heads when using ARP studs

1. Follow ARP’s Torque Procedure:

   • ARP specifies a final torque value of 38 ft-lbs when using their lube.
   • Torque the nuts in two equal steps, following the sequence outlined in the ARP installation manual.

2. Verify Fitment:

• Ensure the cylinder heads are seated properly before proceeding with final assembly.

Torquing the cylinder head fasteners

Step 5: Post-Build Maintenance

• Retorquing the Heads:
• Some engine builders recommend retorquing your Porsche cylinder heads after the engine break-in period, typically done alongside a valve adjustment.
• However, ARP states that this step is not mandatory.

Final Thoughts

Replacing head studs during an engine rebuild is essential for ensuring long-term reliability and preventing failures. High-performance studs like the ARP 204-4206 provide the ultimate peace of mind, allowing you to focus on enjoying your air-cooled Porsche.

For a full walkthrough of the process, watch our video: Replacing Head Studs in Air-Cooled Porsche Engines. If you have any questions or need advice, leave a comment—we’re here to help.

Watch the Video Now!

Installing the cam towers

How to Assemble Piston and Cylinder Assemblies for Optimal Engine Performance

Once your pistons, rings, and cylinders are properly cleaned and prepped, it’s time to move on to assembly. In our latest YouTube video, we demonstrate the key steps to assemble piston and cylinder assemblies. Follow this guide for a thorough breakdown of the process to ensure your engine build is set up for success.

Pre-Assembly Preparation

Before starting, make sure all components are ready:

• Clean Components: Cylinder bores should be cleaned with denatured alcohol and Kimwipes to remove all residue.
• Ring Gaps: Piston ring gaps should be measured and adjusted as necessary.
• Wire Locks Installed: Install wire locks on one side of your pistons prior to assembly.

Proper piston ring orientation

Key Considerations for Piston Rings

1. Check for Directionality:

   • Many piston rings are directional. Look for markings such as “TOP” to ensure they are installed correctly.
   • Note: “TOP” indicates the orientation, not the position on the piston.

2. Match Rings to Grooves:

   • Ensure each ring is fitted to the correct groove. Rings of the same thickness may differ in function, so consult the manufacturer’s instructions.
   • Improper placement or orientation can lead to oil consumption, blow-by, and cylinder bore scuffing.

3. Radial Back Clearance:

• Verify that no part of the ring’s inside diameter protrudes beyond the piston ring land. Insufficient clearance can cause severe engine damage.

Piston ring radial back clearance

Installing Piston Rings

While many manufacturers recommend using ring pliers, many engine builders prefer the “walk” or “spiral” method:

1. Start with the oil control ring.
2. Gently spiral the ring onto the piston, taking care not to bend, distort, or break it.
3. Proceed with the second ring, then the top ring.

Staggering Ring Gaps

Once the rings are installed, stagger the end gaps to prevent alignment. Misaligned gaps can lead to blow-by and reduced compression.

Using a Ring Compressor

Modern thinner rings require extra care during installation. We recommend using a tapered sleeve ring compressor for better control and reduced risk of damage:

1. Lubricate the Components:

   • Apply lubricant to the piston skirts, rings, and the inside of the tapered sleeve compressor.

2. Load the Piston:

   • Push the piston into the tapered sleeve until the skirt protrudes slightly.

3. Prepare the Cylinder:

   • Lubricate the cylinder bore and position the ring compressor on top.

4. Insert the Piston:

   • Slide the piston through the tapered sleeve into the cylinder bore, applying gentle, even pressure.
   • Hold the tapered sleeve firmly to prevent gaps between the sleeve and the cylinder.

5. Adjust if Needed:

• If the piston stops or the ring catches, stop immediately. Reposition the sleeve and try again.
• Alternating pressure at the top and bottom of the piston crown can help guide the rings into the bore.

Installing the piston using a tapered sleeve ring compressor

Final Steps

With the piston fully seated in the cylinder, your assembly is ready to be installed onto the engine. Take your time and double-check your work to avoid costly mistakes.

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Final Thoughts

Proper assembly of pistons and cylinders is crucial for engine performance and longevity. By following these steps and using the right tools, you’ll minimize the risk of damage and ensure your engine operates smoothly.

For a full visual walkthrough, watch our video: How to Assemble Piston and Cylinder Assemblies. If you have any questions or need advice, leave a comment—we’re here to help.

Watch the Video Now!

Installing Piston and Cylinder Assemblies: A Step-by-Step Guide

With your short block complete and ARP head studs installed, the next step is assembling and installing your pistons and cylinders. This process is critical for ensuring proper deck height and a reliable engine build. Our latest YouTube video walks you through this procedure. Below is a detailed guide to help you achieve success.

Step 1: Check and Adjust Deck Height

Deck height—the distance from the piston crown to the top of the cylinder—is a crucial measurement. Follow these steps to check and adjust it:

1. Temporary Assembly:

   • Install one piston and cylinder assembly without sealant, base shims, or gaskets.
   • Push the piston through the cylinder to expose the wrist pin bore.
   • Optionally, pre-install the wrist pin into one piston boss for easier alignment.

2. Align with the Connecting Rod:

   • Slide the assembly onto the engine and line up the piston with the connecting rod.
   • Lubricate and insert the wrist pin through the rod, but do not install the wrist pin clip yet. This assembly will be removed later.

3. Measure Deck Height:

   • Rotate the engine to bring the piston to top dead center (TDC). Hand-feed the timing chains to prevent them from binding.
   • Measure the deck height using a specialized deck height tool or a dial/digital caliper.
   • Target Deck Height: 1 to 1.5 mm. If it is less than 1 mm, base shims will be required.

4. Select Base Shims:

• LN Engineering offers copper base shims in 0.25 mm, 0.5 mm, 0.75 mm, and 1 mm thicknesses. Choose the correct thickness to achieve the desired deck height.

Step 2: Prepare for Final Assembly

1. Disassemble and Clean:

   • Remove the piston and cylinder assembly.
   • Clean the cylinder base and case deck using denatured alcohol and Kimwipes to ensure a spotless surface.

2. Apply Sealant:

• Use a non-hardening sealant on the cylinder base. If using base shims or gaskets, apply sealant to both sides.
• Recommended Sealants:
• Elring Curil T (used in this guide)
• Curil K2
• Dow Corning 730 (top pick by most engine builders, but $$$)

Step 3: Final Assembly

1. Install the Assembly:

   • Slide the cleaned Porsche piston and cylinder assembly back onto the engine, aligning the wrist pin bore with the connecting rod.
   • Insert the wrist pin into place and install the second wrist pin clip.

2. Secure the Clips:

   • Before installing the second clip, cover all openings in the engine case to prevent accidental loss of the clip inside the engine.
   • Verify that both sides of the piston have wrist pin clips installed securely.

3. Seat the Cylinder:

• Push the cylinder firmly onto the engine case. Use a Porsche cylinder hold-down nut to secure the assembly until the heads are fitted.

Step 4: Repeat for Remaining Assemblies

Repeat the process for all remaining piston and cylinder assemblies before proceeding to install your Porsche cylinder heads.

Tips for Success

• Take Accurate Measurements: Proper deck height ensures optimal engine performance and prevents damage.
• Handle Clips Carefully: Wrist pin clips can easily eject during installation. Always work with caution and keep spares on hand.
• Use High-Quality Tools and Materials: Proper tools and sealants make the process smoother and more reliable.

For a detailed demonstration of this process, check out our video: Installing Piston and Cylinder Assemblies. If you have any questions or need further guidance, leave a comment—we’re here to help.

Watch the Video Now!

The Importance of Light Checking Piston Rings and Verifying Oil Control Ring Tension During Engine Break-In

Proper piston ring seating during engine break-in is essential for ensuring optimal performance and longevity. In engines with Nikasil-plated cylinder bores, this process is even more critical due to the unique properties of the Nikasil surface. Our latest YouTube video walks through the steps for light checking piston rings and verifying oil control ring tension to achieve a perfect break-in. Here’s a detailed guide based on the video.

Why Proper Cylinder Preparation Matters

Nikasil-plated bores are highly durable, but they do not wear in the same way as iron cylinder bores. Proper surface preparation, including achieving a plateau hone, is critical for ensuring the rings seat correctly. If the surface finish or cylinder concentricity is off, the rings may take longer to seat—or fail to seat entirely. This can be verified with a profilometer, in this case a Mitutoyo SJ-210 using Traceboss software.

Likewise, cylinder geometry must be verified using a bore gauge to ensure cylinders are within tolerance with no more than .002" of ovality and taper.

Step 1: Light Checking Piston Rings

Light checking involves ensuring the rings create a light-tight seal with the cylinder walls, confirming proper fit and sealing potential.

1. Preparation:

   • Ensure cylinders are properly honed and cleaned.
   • Gap the piston rings according to specifications.

2. Performing the Light Check:

   • Place the piston ring in the cylinder bore.
   • Shine a light behind the ring and inspect for light passing between the ring face and the cylinder wall.
   • A light-tight fit indicates proper contact and sealing.

3. Key Considerations:

• Top Rings: These are typically OD-lapped and rarely fail the light-tight test unless the ring size is incorrect.
• Second Rings: These are critical for secondary oil control. If they fail the light-tight test, the engine may experience increased oil consumption and smoke.
• Oil Control Rings: Light checking is not necessary, but radial tension is an important factor to verify.

Step 2: Measuring Oil Control Ring Tension

Proper oil control ring tension ensures effective oil management and prevents excessive consumption or blow-by.

1. Setup:

   • Clean and lubricate the cylinder and the oil control ring.
   • Install the oil control ring onto the piston and fit it into the cylinder.

2. Measuring Tension:

   • Use a fish scale, luggage scale, or trigger pull scale to measure the force required to move the piston through the cylinder.
   • Focus on measuring the constant force (not the breakaway force) applied during the movement.

3. Target Tension for Nikasil Bores:

   • Low-tension piston rings are common in modern engines, with an average radial tension of 8 lbs compared to 20 lbs for standard rings.
   • For Nikasil bores, aim for approximately 10 lbs of radial tension, as tension typically drops by 1 lb after break-in.

4. Adjusting Tension:

   • Experienced builders can fine-tune tension by swapping out rails or modifying oil rail expanders.
   • Applications may require more or less tension depending on specific engine requirements.

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Why These Steps Are Essential

• Light Checking: Ensures optimal ring seal, critical for compression and oil control during engine break-in.
• Verifying Tension: Prevents over- or under-tensioning, which can lead to oil consumption issues or ring failure.

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Final Thoughts

By light checking your piston rings and verifying oil control ring tension, you set the foundation for a successful engine break-in. These steps are especially important for engines with Nikasil bores, where surface preparation and precision are non-negotiable.

Regardless of whether or not you are rebuilding an aircooled or watercooled Porsche engine, be sure to download AND read out detailed Porsche engine assembly and break-in procedures and guidelines.

For a detailed walkthrough, watch our video: Light Checking Piston Rings and Verifying Oil Control Ring Tension. If you have any questions or insights from your own experience, leave a comment—we’d love to hear from you!

Watch the Video Now!