1988 Porsche 911 Turbo Cabriolet M505 Slant Nose (Lot 85)

Description

OFFERED WITHOUT RESERVE

Globally respected for top-flight, air-cooled Porsche engine development and service, Thoroughbred Motorsports of Corry, Pennsylvania, was founded by Dr. Karl Hens — a man whose experience and knowledge have been honed by a lifetime dedicated to building precision Porsche powerplants. Along his journey of automotive excellence, Dr. Hens amassed a collection of special air-cooled Porsche sports cars spanning every generation, alongside a nearly immeasurable treasure trove of highly sought-after Porsche parts.

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The 1988 Porsche 911 Turbo Cabriolet ordered in the rare M505 slant-nose configuration was one of the most distinctive iterations of the legendary 930 platform. Derived from Porsche's 935 race program, the slant-nose treatment reshapes the front fenders with pop-up headlamps and integrated fender-mounted turn signals, giving the car a purposeful, aerodynamic profile unlike any standard 911. Beneath the flared bodywork sits the iconic 3.3-liter turbocharged flat-six, delivering forceful power through a single KKK turbocharger and paired with Porsche's robust four-speed manual gearbox.

As a 930 Cab, it combines open-air touring with the 930's legendary turbocharged character, while the factory-order M505 package ensured genuine rarity, hand-finished bodywork, and exclusivity among contemporary 911s. In 1988, the option cost roughly $24,000, making it an exceptionally expensive addition and helping explain the low production numbers. To say that these M505 Slant Nose cars were icons in their own time is an understatement.

Moreover, this example was equipped with significant additional equipment adding up to a $117,608 MSRP when the car was new. Optional features fitted when the car was new include electrically adjustable sports seats, a steering wheel with a raised center hub, and an electric roof catch.

This Grand Prix White M505 Flachbau Cabriolet was issued a salvage title in New York in 1998. Fitted with an oversized K27 turbocharger, a common period modification, the car also features an ANDIAL fuel enrichment system and engine control unit.

Following the current owner's acquisition in the early 2000s, the car's wheels were refinished.

This 1988 Porsche 911 Turbo Cabriolet M505 Slant Nose is now represented at no reserve by a Broad Arrow Specialist in Georgia with a tonneau cover, service records, a Porsche Certificate of Authenticity, a CARFAX Vehicle History Report, and a clean Pennsylvania title in the current owner's name.

Highlights

• Offered from the Thoroughbred Motorsports Collection 

• Factory M505 slant-nose (Flachbau) bodywork with pop-up headlamps 

• Cabriolet convertible top with power-operated mechanism 

• Finished in Grand Prix White over a Black leather interior 

• Sports seats with partial power adjustment 

• 3.3-liter (3,299cc) turbocharged flat-six engine with K27 turbo 

• ANDIAL fuel enrichment system/engine control and intercooler 

• Four-speed manual transmission 

• Porsche Certificate of Authenticity (POA)

Factory Equipment

• 930 wide-body rear fenders 

• “Tea-tray” rear spoiler for enhanced high-speed stability 

• Fuchs forged alloy wheels, staggered front/rear 

• Air conditioning

• The M505 “Flachbau” (Slant Nose) option for U.S.-spec cars included: 

  • Flat (slant) front fenders replacing the standard 911 fenders 

  • Pop-up headlights 

  • Functional front-fender louvers/vents behind the front wheels 

  • Special front spoiler valance designed specifically for the Flachbau body 

  • Extended rocker panels/side skirts  

  • Rear quarter-panel brake-cooling vents  

  • Boxed rocker ductwork and vent plumbing for rear brake-cooling system  

• Factory options adding up to an MSRP of $117,608 when new on this M505 include: 

  • Electric Roof Catch 

  • Sport Seats, Electric - L/R 

  • Limited Slip Differential 

  • Steering Wheel with Raised Hub 

  • Tonneau Cover - Cabriolet 

  • Slant Nose Body Option 

  • Wheel Centers - Grand Prix White 

  • Amplifier System 

  • Alarm System 

  • CD-Player "CD-01" with Radio

Modifications

• ANDIALfuel enrichment system/engine control  

• ANDIAL intercooler 

• Larger K27 turbocharger

Servicing

• The car's wheels were refinished in 2004

Known Imperfections

• The accompanying CARFAX Vehicle History Report indicates a Salvage title brand was issued in New York in 1998 

• While reasonable efforts were made during preparation for the sale, due to the volume of vehicles in this collection, it was not possible to diagnose or detect all imperfections present. Please refer to the photo gallery. 

• Some wear on leather upholstery and interior surfaces

Included Items

• Porsche Certificate of Authenticity (POA) 

• Some service records 

• Tonneau cover 

• Jack, air compressor, and tool kit

Ownership History

This 1988 Porsche 911 Turbo Cabriolet M505 Slant Nose is offered from the Thoroughbred Motorsports Collection of no-reserve automobiles.  

The CARFAX Vehicle History Report begins in 1994 and lists Pennsylvania, California, and New York registration history.

Additional Information

The seller states, “Purchased at a Porsche gathering in California, this was one of two cars acquired at the same time. A salvage history was uncovered the night before the transaction. Performance upgrades included an Andial fuel enrichment and engine management system, an Andial intercooler, and a larger K27 turbocharger. Dangerously fast. Opportunity of a lifetime.”

A Broad Arrow Specialist is working as an agent on behalf of the seller of this listing. As such, the purchase transaction will be facilitated by Broad Arrow, including vehicle payment, applicable taxes required to be collected by the seller or Broad Arrow, and title/ownership reassignment. Broad Arrow is a wholly-owned subsidiary of Hagerty.

Contact: Ramsey Potts Phone: 912.508.4096 Email: rpotts@hagerty.com

Note to Bidders – Thoroughbred Collection

All Lots are offered “as is, where is.” Descriptions are based on information provided by the seller and third-party sources; the seller, its agent, and Hagerty Marketplace do not make any representations or warranties, express or implied.

This Collection includes a wide variety of items—complete and project vehicles, engines, parts, tools, shop equipment, and memorabilia—each with unique condition and intended-use considerations. Bidders are encouraged to inspect each Lot or conduct any desired due diligence before bidding to ensure it meets their expectations for functionality, completeness, and authenticity. Please review the Marketplace Terms of Use and contact us with questions about specific inclusions, particularly for grouped items.

Taxes & Fees:

As a reminder, auction lots on Hagerty Marketplace carry a bidder’s premium that is 7% of the final sale price, $500 minimum. In addition, applicable Georgia sales tax (7%) will be collected on non-vehicle purchases after an auction, unless the buyer qualifies for an exemption.

Buyers are responsible for all taxes, export/import duties, and compliance requirements. Valid resale or export documentation must be provided before payment to claim any exemptions.

Invoicing:

Please note that invoices will be sent by the seller’s agent to all buyers in November 2026.

Shipping:

All items are FOB Hagerty Garage + Social, Savannah, Georgia, and must be removed within a reasonable time following payment. Shipping may be coordinated through Kevin Allen, American Moving & Storage (912.856.4644) at the buyer’s expense. For questions regarding pick-up scheduling or on-site logistics, contact Marvin Waters at 910.315.2918.

Holiday Closures:

No pickups allowed on the weekend of Thanksgiving November 25-29

Legal Notice:

Purchase transactions are facilitated directly between buyers and sellers, with the assistance of Broad Arrow as seller’s agent. Hagerty Marketplace is not a party to any sale transaction.

All auction listings on Hagerty Marketplace are created using information provided by the seller. The Marketplace team and the seller have reviewed all information for accuracy to the best of their abilities. Bidders are ultimately responsible for conducting their own due diligence before placing a bid, including verifying details, condition, registration requirements, and compliance with applicable laws. For any questions or additional information, contact the seller.