Porsche 911 991 GT3 RS Engine Camshaft Inspection Guide
The moment you hear a faint tick from the engine bay or notice a camshaft deviation creeping past 6 degrees, you know it’s time to pull the cam covers and inspect the finger followers—the 991.1 GT3 RS’s most well-known weak point.
TL;DR
The 991.1 GT3 RS uses a hydraulic finger follower valvetrain with DLC-coated camshaft lobes, and wear on the follower pads is the critical issue to monitor . Inspection requires removing the cam covers (no borescope shortcuts—you can’t see enough to properly evaluate wear) and checking all 24 finger followers for DLC coating breakthrough . Early wear shows as a dull grey patch on the follower pad; advanced wear damages the camshaft lobes, and on G-series engines, DLC-coated camshafts cannot be reground—they’re replacement-only . The 991.2 engine switched to solid lifters without DLC coating on the cams, addressing the root cause . Always have this inspection performed by a Porsche specialist with proper documentation.
Key Takeaways
- The 991.1 GT3 RS (and GT3) uses hydraulic finger followers that are prone to DLC coating wear, especially at high RPM
- Inspection requires removing the cam covers—borescope inspection is unreliable and can miss early wear
- Check all 24 finger followers for DLC coating breakthrough: a healthy pad has a uniform, dark, mirror-like finish
- Early wear = grey witness patch on the follower pad; advanced wear = scored cam lobes and possible engine failure
- G-series camshafts are DLC-coated and cannot be reground—once the coating is compromised, replacement is the only option
- 991.2 engines (G6 and later) switched to solid lifters and removed DLC from the cams, eliminating the root cause
- Always use performance features responsibly and follow local driving laws. Have any engine work performed by qualified Porsche technicians.
Why the 991.1 GT3 RS Has This Issue
Here’s the engineering reality. The 991.1 GT3 RS engine revs to 9,000 RPM—that’s superbike territory . At those engine speeds, the hydraulic finger followers can experience following error, meaning the follower briefly loses contact with the cam lobe. When contact resumes, the micro-impacts cause wear on the DLC coating .
Porsche addressed this in stages:
- Early fix: Lower RPM limits, higher oil pressures, and improved oiling
- G6 engines: DLC-coated camshafts to better resist wear
- 991.2 engines: Solid lifters (no hydraulic element) and removed DLC from camshafts—the follower design was fundamentally changed
The 991.2 solution is the permanent fix. But the 991.1 GT3 RS remains a special car, and owners need to inspect and maintain the valvetrain proactively.
“The coating doesn’t heal. Inspection is a recurring appointment, not a box you tick once.” — Dundon Motorsports
Step-by-Step Inspection Guide
Step 1: Remove the Cam Covers
This is the critical first step. You need full visual access to all 24 finger followers and their corresponding cam lobes. Porsche’s workshop manual on techinfo.porsche.com (PIWIS) provides the official procedure for removing and installing the cylinder head covers on this engine .
Tools needed:
- Porsche’s special tool—the “chopsticks”—for cam cover removal
- New cam cover gaskets (always replace)
- Proper sealant (Loctite 518 is widely recommended by the community)
Step 2: Inspect Each Finger Follower
Rotate the engine by hand so you can see the full sweep of each follower’s contact pad .
What a healthy follower looks like:
- Uniform, dark, almost mirror-like finish on the DLC contact pad
- No grey patches, no texture, no edges
What early wear looks like:
- A dull, grey witness patch in the middle of the contact pad where the cam lobe sweeps
- The edges of the patch often look like a “shoreline” between dark coating and grey steel
- This means the DLC coating has been polished through and bare steel is exposed
What advanced wear looks like:
- The grey patch grows and develops texture you can catch a fingernail on
- The matching cam lobe shows lines or scoring
- Oil analysis iron is usually elevated by this point
What failure looks like:
- Pitted or galled follower pads
- Visibly stepped or scored cam lobes
- Misfires, ticking sounds, or check engine lights
Step 3: Inspect the Camshaft Lobes
Every cam lobe tells you what the follower has been doing. Inspect each lobe for:
- Scoring or scuffing
- Discoloration
- A visible wear step (the lobe surface isn’t smooth)
Critical G-series warning: On G-series engines, the camshaft lobes are DLC-coated just like the followers. Once that coating is compromised, there’s no grinding it back—the camshaft is replacement-only . E- and F-series cams can sometimes be saved by regrinding, but G-series cannot .
Step 4: Document Everything
Photograph every follower and every suspect lobe . These photos become your baseline for the next inspection. Wear is a trend—trends need data points .
Label photos by cylinder number and intake/exhaust so you can compare over time.
Step 5: Replace What’s Worn
Replace any follower that isn’t perfect . You can remove and replace finger followers without removing the camshafts—as you rotate the cam, you release pressure on the follower, allowing removal .
Part numbers:
- Intake finger follower: 9A1 105 035 91 (roughly $100 each)
- Exhaust finger follower: 9A1 105 036 91 (roughly $100 each)
If camshafts need replacement, that’s a significantly larger job.
The Cost of Waiting vs. Acting Early
| Scenario | Parts Involved | Ballpark Outcome |
|---|---|---|
| Caught early | Finger followers only (~$100 each, 24 total) | Followers replaced during planned service. Camshafts untouched. Car back on track. |
| Caught late | Followers + camshafts + possible metal contamination | Thousands in parts (if camshafts are available—supply has been months-long), tens of thousands in labor. |
| Not caught | New engine or full rebuild | Engine-out, five-figure rebuild or replacement. Out of warranty, that’s all you. |
The economics are clear: replacing followers early is the cheapest insurance in Porsche ownership .
991.1 vs. 991.2: What Changed
Porsche made significant valvetrain changes in the 991.2 GT3 RS to address the finger follower issue:
| Feature | 991.1 GT3 RS | 991.2 GT3 RS |
|---|---|---|
| Lifter Type | Hydraulic finger followers | Solid lifters (no hydraulic element) |
| Camshaft Coating | DLC-coated (on G-series) | No DLC coating on cams |
| Root Cause Addressed | No—inspect and replace | Yes—following error eliminated |
| Inspection Urgency | High—recurring inspection required | Lower—fundamentally more robust design |
The 991.2’s solid lifter design eliminates the hydraulic following error that caused the wear . This is the key reliability improvement between generations.
FAQ
What are finger followers and why do they matter on the 991.1 GT3 RS?
Finger followers are the levers that transfer camshaft motion to the valves. On the 991.1, they use hydraulic elements that can lose contact with the cam at high RPM, causing wear .
Can I use a borescope to inspect the followers instead of removing the cam covers?
No. Community experts strongly advise against borescope-only inspection—you simply can’t see enough to properly evaluate the lobes and followers, and early wear is invisible .
How often should I inspect the finger followers?
Depends on usage. Track-heavy cars should be inspected at least annually. Road cars can go longer, but any out-of-warranty 991.1 should have a baseline inspection .
What does early wear look like on a finger follower?
A dull, grey patch on the contact pad where the DLC coating has been polished through. The healthy surface is dark and mirror-like .
Can camshafts be repaired or reground if worn?
G-series camshafts cannot be reground—the DLC coating is integral, and once compromised, replacement is the only option. E- and F-series cams can sometimes be reground .
Did Porsche fix this issue in later engines?
Yes. The 991.2 engine uses solid lifters and removed DLC coating from the camshafts, addressing the root cause of the wear .
What should I do if I’m buying a used 991.1 GT3 RS?
Include a complete finger follower inspection in the pre-purchase inspection. Ask for labeled photos and records of any prior follower replacement .
The Bottom Line
The 991.1 GT3 RS is a phenomenal car with a well-documented valvetrain vulnerability. The finger followers are the wear item—they’re relatively inexpensive, but the labor to inspect them is significant. Catching wear at the follower stage means you never have to have the camshaft conversation . If you own one of these cars, establish a baseline inspection, monitor oil analysis for iron content, and replace followers before they damage the camshafts. The 991.2 fixed the design, but the 991.1 remains a special machine that rewards proactive maintenance.
What’s your experience with 991 GT3 RS valvetrain maintenance? Share your insights in the comments.
References:
- Dundon Motorsports – 991.1 GT3 Finger Follower Inspection & Wear Guide
- Rennlist – 2016 991.1 GT3 RS DIY Engine-Out Finger Follower + Cam Replacement
- Rennlist – 991.1 GT3 Finger Follower Repair (F-Series Engine)
- Rennlist – Finger Follower Inspection Discussion (Borescope Limitations)
- Rennlist – G6 Engine Finger Follower Teardown
