Porsche Bore Scoring & Block Repair in Colorado
A Porsche 3.4 case half set up on the CNC.
Bore scoring on a Porsche flat-six isn't something an oil change or a bottle of additive is going to fix. Once the cylinder wall is damaged, the engine has to come apart and the cylinder has to be machined. That's what we do. ASF Machine does Porsche bore score repair in-house in Grand Junction, Colorado, for owners on the Western Slope, the Front Range and anywhere else that would rather ship it in. We do our own sleeving on Porsches, and the sleeving, boring and block indexing are done on a CNC.
If you want the deep dive on why these engines score in the first place, read our technical article, Scored Sixes: Porsche 9A1 Bore Scoring Explained. This page is the short version: what it is, what it looks like, and how we fix it.
What Porsche Bore Scoring Is
Porsche's water-cooled flat-sixes don't come with iron liners. The bores are aluminum-silicon: hard silicon particles exposed at the bore surface carry the piston and rings on a film of oil, and a coating on the piston skirt keeps aluminum from rubbing on aluminum. When that system breaks down, you get bore scoring: galling, metal transfer and grooves worn into the cylinder wall.
The 1997–2008 M96/M97 engines (Lokasil bores) are the famous ones. The 2009-and-later 9A1, with its closed-deck Alusil block, gets it much less often, according to Hartech in the UK, which also reports that the 9A1 failures it has seen were seizures low in the bore rather than the classic one-sided scoring. Lower rates still aren't zero, and nobody has published real failure-rate numbers.
Symptoms That Bring a Porsche In
Here's what we see on the Porsches that come in, and what to watch for on yours. These are signs that can point to bore scoring, not proof of it:
- Oil use that keeps climbing.
- A tick that sounds like a lifter, or a knock that's worst from cold. Often that's piston slap from the extra clearance the scoring has opened up.
- Misfires or a check engine light.
- One tailpipe sootier than the other.
- Shiny aluminum debris in the oil filter.
A borescope through the spark plug hole is a good next step, but it can miss damage low in the bore. Add a leak-down test and/or a compression test, coupled with a used oil analysis, and together those can help diagnose an issue. They point to it; they don't prove it. The only way to know for sure is to inspect it.
A borescope look at a bore with light wear from a lot of stop-start driving early on, not scoring. A borescope is a good first look, but it can miss damage low in the bore.
How We Repair a Scored Porsche Block
A Porsche 3.4 case being converted to a 3.8.
Flanged ductile iron liner installed and finished.
Converting a 3.4 to a 3.8 with flanged ductile iron liners.
Our repair is a flanged ductile iron liner, fitted at a slight interference, with a special chemical compound between the liner and the parent bore for heat transfer. It's still a dry liner. The sleeving, boring and block indexing are done on a CNC.
For more on why the finish inside a bore matters, see our cylinder bore finish guide.
Why a Liner?
There's more than one honest way to fix a scored Porsche bore. Some shops overbore the original Alusil bores and Nikasil-plate them, and the shop that offers it says most 9A1 blocks don't need sleeving at all. Hartech in the UK fits complete replacement alloy cylinders. Ductile iron liners for these blocks are an established option too, sold by Design911 for the 991 Carrera S 3.8.
Some well-respected Porsche specialists, Hartech and Flat 6 Innovations among them, aren't fans of iron liners, mostly over the extra cold clearance an iron bore needs. Fair point to raise, and here's our take: "There's nothing wrong with fitting a forged piston at .003" piston to cylinder wall, yes it will make little bit of noise when cold but if it uses an offset wrist, that often quiets the assembly down."
3.4 to 3.8, or 4.0
If the case is apart and getting new liners anyway, it's worth talking about displacement. A 3.4 can be made into a 3.8, and into a 4.0 with a crank change. Either way, it needs a tune after.
Engines We Work On (2009+ 3.4, 3.6 & 3.8)
We work on the 2009-and-later 9A1 engines in 3.4, 3.6 and 3.8 form:
- 3.4: 987.2 Boxster S & Cayman S, 981 Boxster S & Cayman S, 991.1 Carrera
- 3.6: 997.2 Carrera
- 3.8: 997.2 Carrera S, 991.1 Carrera S
This page doesn't cover the base-model 2.7 and 2.9. If you've got a 981 GT4 or Spyder, a 997.2 Turbo or a 991 GTS, call us before you ship anything and we'll talk it through.
Block Only or Full Engine?
All three. Send us the bare block for machine work, bring us the whole engine for a full rebuild, or bring the car and we'll pull the engine.
Shipping it in? Don't box anything up yet. Contact us for shipping instructions first, and we'll tell you how to send it.
Before you price out "just the bores," though, here's what we've seen: I've yet to tear one down that didn't also have other issues like a broken rod or a bad rod bearing. That's why we'd plan on a full teardown & inspection on any scored engine, not just a bore repair.
FAQ
Can Porsche bore scoring be fixed without rebuilding the engine? No. Once the cylinder wall is scored, no oil, additive or flush puts it back. The engine has to come out and come apart, and the cylinders have to be machined.
Do 997.2, 981 and 991 engines get bore scoring? Yes, though much less often than the earlier M96/M97, according to Hartech. Nobody has published hard failure-rate numbers for the 9A1.
Is the 3.4 or the 3.8 more likely to score? The sources we trust don't publish rates by engine, so we won't guess. LN Engineering reports scoring in both the 3.4 and the 3.8.
Can you turn my 3.4 into a 3.8 or 4.0 while it's apart? Yes. A 3.4 can be made into a 3.8, and into a 4.0 with a crank change. Either way, it needs a tune after.
Which Porsche engines do you repair? 2009-and-later 9A1 engines in 3.4, 3.6 and 3.8 form: 987.2 and 981 Boxster S & Cayman S, 997.2 Carrera & Carrera S, and 991.1 Carrera & Carrera S.
Do you repair just the block, or does it have to be the whole engine? All three: bare block, full engine or the whole car. See "Block Only or Full Engine?" above for why we'd still want to look at everything. If you're shipping it, contact us for shipping instructions before you send anything.
How long does a Porsche block repair take? Each one is different, so it varies by job. Call us with what you've got and we'll talk it through.
How can I check a Porsche for bore scoring before I buy it? Listen for a lifter-like tick or a cold knock, check for one sooty tailpipe, look for aluminum debris in the oil filter, and have someone who knows these engines scope the bores and run a leak-down test and/or a compression test, coupled with a used oil analysis. Together those can help diagnose an issue. Keep in mind early scoring sits low in the bore and can hide from a scope, so only a teardown and inspection confirms it.
How do I keep my Porsche from scoring its bores? Warm it up before you lean on it. It's always best to let oil temp reach 155-160° F before you apply any throttle more than ambulation requires. In other words, just enough throttle to get the car moving gently until the oil is up to temperature.
Let's Talk About Your Porsche
If your Porsche is using oil, knocking cold or has already been scoped, drop us the details: model, engine, miles and what you've seen. We'll tell you what we'd do and why. We've been doing machine work at ASF since 1996. Call 970-242-0919 or fill out the form below. Shipping a block, case or engine? Please get shipping instructions before you send it.