997 Bore Scoring: Is It Really "Not If but When"?

Opinion. Market data from Bring a Trailer and Cars and Bids results and Hagerty Price Guide values, all checked October 29, 2026. Owner data from our count of 98 Rennlist owner reports.

The question

Bore scoring on the 997.1 is often described as "not if but when." Yet 997.1 prices on Bring a Trailer are higher now than they were before 2021. If every engine is going to score, why are buyers paying more? Maybe the risk is smaller than the warnings suggest. Maybe the market is pricing it in a way that is easy to miss.

This piece looks at what the data says about how common scoring is, what the market is doing, and what we think is going on. Where it is our opinion, we say so.

How common is it?

The honest answer is that nobody knows. Porsche has not published a number, and no study we could find has followed a random set of 997s over time.

What exists are views from people who see a lot of engines, plus owner reports.

• The strongest claim comes from a rebuilder. In 2013, Hartech's Baz Hart, a UK engine rebuilder, wrote on the 911uk forum that "almost all" 996 3.6 engines and pre-generation 2 997 engines "will eventually score bores". That is where much of the "not if but when" talk comes from. A rebuild shop sees the engines that failed, so its view is useful but not a sample of all cars.
• An inspector sees a much lower number. Porsche Inspections, a UK pre-purchase inspection service, says it has seen "perhaps 5%" of the 2004 to 2009 generation 1 cars it inspected with early warning signs of bore scoring, and that "it isn't something you should avoid the model for." It does not borescope, so that is an estimate based on outside signs.
• Owner reports cannot give a rate. In the Rennlist thread we counted, 50 of 98 owner reports described scoring. That share is high because owners with a problem are more likely to post.
• A forum poll is not a rate either. A Rennlist poll shows 146 "yes" and 543 "no" votes for the 997.1, and 18 "yes" and 305 "no" for the 997.2, from 1,012 voters. These are self-selected forum votes. Nobody checked them.

Where owners did give a mileage, the median when scoring was found was 60,000 miles (42 reports). That is when they found it, not when it started. Cylinder 6 came up in 22 of the 29 scoring reports that named cylinders, which matches LN Engineering's note that scoring on these engines is most common on bank 2, cylinders 4 to 6.

The 997.2 can score too

LN Engineering lists the 2009 to 2012 Carrera and Carrera S 9A1 engines among the Alusil engines that can score, and says that in its experience these engines are affected at significantly lower rates than the earlier Lokasil M96/M97 engines. Hagerty's buyer's guide says the 9A1 "seems to suffer from this malady far less often". In our Rennlist count, 6 of the 13 997.2 owner reports described scoring. Thirteen reports is far too few to compare the two generations.

Why the difference? The 997.1 uses Lokasil bores, where a silicon-rich insert is cast into the cylinder area. The 997.2's 9A1 block is cast from Alusil, a high-silicon alloy all the way through. LN Engineering says the 9A1 is also a closed-deck engine, and it links 997.2 scoring mainly to bores shrinking near the main bearing saddles and the bore surface breaking down. On the 3.6 and 3.8 M96/M97, LN points to the longer stroke, with pistons that extend about 7 mm out of the bore at bottom dead center, as a likely reason for more side loading.

What the market is doing

We pulled every completed auction on Bring a Trailer's 997 page (3,208 results) and kept the Carrera, Carrera S, Carrera 4, Carrera 4S and Targa cars. We left out the Turbo, GT2, GT3, GTS and special editions. Prices are the winning bid, before the buyer's fee. To sort manual from automatic, we opened all 1,052 sold 997.1 listings and the 2024 to 2026 997.2 Carrera S and Carrera 4S listings, and read the gearbox from each listing's details list.

Sold cars only, coupes and cabriolets together, any mileage. The Carrera S column excludes the Carrera 4S. Medians move with the mix of cars sold each year, and they are not adjusted for inflation. The 2021 Carrera S median ($50,598.50) is rounded to $50,599. Source: Bring a Trailer, Porsche 997 completed auctions.

The 997.1 market jumped in 2021, dipped in 2023 and 2024, and has climbed again since. Hagerty also reports 997 values rising. In July 2025 it put the average condition 3 value of a 997 at $92,900, up 34% since 2020. That average covers every 997, GT cars included.

The 997.2 gap

The clearest sign that buyers price the 997.1's engine is the gap to the 997.2. To keep it close to like for like, we compared manual cars of the same model sold over the same three years.

The 997.2 samples are small. Source: Bring a Trailer.

Mileage explains only part of it. The 997.1 Carrera S coupes had a median of 49,000 miles (123 of 125 listings gave a figure) against 41,000 for the 997.2s (all 28). When we split the same cars by miles, the 997.2 still sold for more in every group.

Mileage as stated in each listing's details list. Each 997.2 group has 12 cars or fewer, so treat these as a rough check, not a measurement. Source: Bring a Trailer.

Hagerty's Price Guide points the same way. These are Hagerty's value estimates, not sales. In October 2026 it showed these ranges for the coupe:

Sources: Hagerty valuation tool pages for the 2006 911 Carrera S and 2010 911 Carrera S, viewed October 29, 2026. Hagerty shows each condition as a low to high range and does not let you pick a gearbox on these pages.

In both #2 and #3 condition, the 2010 range sits about $17,000 above the 2006 range. Over the last year Hagerty's #3 estimate for the 2006 rose faster, but over three years the 2010 rose more.

Cars and Bids could not settle the question. From January 2024 to October 2026 it sold 125 Carrera and Targa 997s (95 997.1, 30 997.2), but only one was a manual 997.2 Carrera S coupe, going by the gearbox shown on each result. The 21 manual 997.1 Carrera S coupes sold there had a median of $47,997, below the Bring a Trailer median for the same kind of car. Source: Cars and Bids past auctions.

Not all of the gap is engine risk. The 997.2 is newer. Its Carrera S makes 385 hp against 355 for the 997.1. It has no IMS bearing, which the 997.1 does (see what 419 owner reports show about 997 IMS failures). Manual 997.2s are also harder to find, because PDK took over after 2008. Hagerty's buyer's guide says the 997.2s are "more valuable, as they're newer and have more durable engines". The same guide says rising 997.2 prices have had a "ride-along" effect on 997.1s.

Buyers are asking

We opened the 40 most recent sold 997.1 Carrera and Targa auctions on Bring a Trailer (July 31 to October 28, 2026). Only 1 of the 40 listing descriptions mentioned a borescope. In 34 of the 40, someone in the comments asked about or discussed borescope results or bore scoring. In one, a commenter wrote that a "bore score inspection" was what would "swing the value on this car considerably."

Does a rebuilt engine pay?

We searched the descriptions of all 1,052 sold 997.1 Carrera and Targa listings on Bring a Trailer for a rebuilt, re-sleeved or replacement engine, then read each match. We found 27 such cars sold between November 2017 and May 2025, leaving out two race cars. Most were Carrera S models. Some engines were rebuilt to 4.0 liters by shops such as Flat 6 Innovations or with LN Engineering Nickies sleeves. Others were stock rebuilds or factory replacement engines.

For 20 of them, at least five cars of the same model, body and gearbox without a rebuilt engine sold on Bring a Trailer the same year. Only 5 of those 20 sold above that year's median for their group. The other 15 sold below it, and the typical rebuilt car sold for about 8% less. That is a small, mixed sample. Rebuilds range from cheap to very thorough, and many of these cars had high miles. But we found no sign that a rebuilt engine earns a premium on Bring a Trailer.

Only four sold 997.1 listings in the same search disclosed known or suspected scoring at the time of sale. That is far too few to measure what scoring does to price.

What we think is going on

This section is our opinion.

We think "not if but when" overstates it. The claim comes from shops that rebuild failed engines, and they are worth hearing. But no one has shown that most 997.1 engines score. The one inspector estimate we found is about 5% with early signs, and most voters in the Rennlist poll said no.

We also think the market is less relaxed than rising prices make it look. A manual 997.1 Carrera S coupe sold for about $25,000 less than a 997.2 over the last three years, and Hagerty's estimates show a gap of about $17,000. Some of that is power, age, mileage and the IMS bearing. We think some of it is bore scoring. And buyers are not taking it on faith. They ask about the bores in most of these auctions.

So our read is that 997.1 prices are rising with the whole 997 market, and buyers handle the engine risk in two ways. They pay less than for a 997.2, and they check the bores before they bid. A clean scope does not mean the engine will never score. It does mean the buyer is not paying a 997.2 price for an unknown. We were surprised that rebuilt engines do not seem to close the gap. Our guess is that buyers cannot easily judge the quality of a rebuild, so they do not pay up for one.

What a buyer or owner should do

• Get a borescope before you buy. LN Engineering says looking only through the spark plug hole can miss early scoring lower in the bore, so ask how the shop will check. Look hardest at cylinders 4 to 6.
• Know what it costs. Few shops publish a price. Edelweiss Autowerks in Wisconsin lists a bore scoring inspection as a $449 add-on for non-turbo cars. Repasi Motorwerks in Connecticut lists its standard Porsche pre-purchase inspection at $500 to $1,500, and says it includes a borescope on M96/M97 engines. In one Rennlist thread, members posted scope prices from $150 to $435. Those are forum posts, not shop price lists. LN Engineering puts a rebuild that includes scoring repair at $15,000 to $30,000 or more, with the block repair alone at $5,000 to $6,000.
• Warm it up gently. LN Engineering advises against long idling to warm up. It says to drive off soon after starting, stay under about 3,000 rpm and avoid full throttle until the oil is fully warm. Hagerty gives similar advice and says cars from cold climates seem to suffer most.
• Change oil often, especially on short trips. LN recommends every 6 months or 5,000 miles, and sooner for short trips, track use or cold climates. LN also sells oil, so keep that in mind.
• A low-temperature thermostat is an option, not a cure. In December 2013, Hartech posted a test on one stock 3.8 997 fitted with six temperature sensors. It drove the same routes on the same day with the stock thermostat, then with its own low-temperature one. With the stock part, the thrust side of bank 2 averaged 5 degrees hotter than bank 1 (98 vs 93). With Hartech's part, the gap was 1.6 degrees (85.4 vs 83.8). The post does not name the unit, but the readings fit Celsius. It was one car, and Hartech sells the thermostat.
• Watch for the signs. Rising oil use, a tick, and one sooty tailpipe (often the driver's side) are the signs owners mention most. See what 98 owner reports show for examples.

Shopping for one? Our 997.1 buyer's guide covers what to pay and what else to check.

What this cannot tell you

• A failure rate. None of the sources here, ours included, measures how many 997.1 engines score.
• How much of the price gap is bore scoring. Power, age, mileage, the IMS bearing and manual scarcity all play a part, and we cannot separate them.
• The whole market. Bring a Trailer and Cars and Bids are two auction sites. Dealer and private sales are not in these numbers. Hagerty's figures are estimates, not sales.

Sources

• Bring a Trailer: Porsche 997 completed auctions (pulled October 29, 2026)
• Cars and Bids: past auctions (searched October 29, 2026)
• Hagerty Price Guide: 2006 Porsche 911 Carrera S and 2010 Porsche 911 Carrera S (viewed October 29, 2026)
• Rennlist: Poll: Scored cylinder failure for your 997, Y or N? (poll checked October 29, 2026)
• 911uk: Bore scoring, what's acceptable? (Hartech post, April 2013)
• Porsche Inspections: useful info
• LN Engineering: what is cylinder bore scoring
• LN Engineering: bore scoring repair costs
• LN Engineering: how to borescope your engine
• LN Engineering: tips on preventing bore scoring
• LN Engineering: are 997.2 9A1 engines susceptible to bore scoring?
• Hagerty: 2005 to 2012 Porsche 911 (997) buyer's guide (February 2026)
• Hagerty: Porsche valuation trends (July 2025)
• PistonHeads: Hartech update on low temperature thermostat tests (December 2013)
• Edelweiss Autowerks: pre-purchase inspection pricing
• Repasi Motorwerks: Porsche pre-purchase inspection
• Rennlist: PPI and bore scoping pricing for a 997 (forum thread, October 2024)