If you own a 1977 Porsche 911 with the 2.7-liter engine and are looking to build a short stroke 3.2-liter, you are tackling one of the most rewarding performance upgrades for an early 911. This conversion combines the 3.2L cylinder bore (95mm) with the 2.7L crankshaft stroke (70.4mm) to create a 3.0-liter engine that revs faster and produces more power than the original. The result is a responsive, high-revving powerplant that retains the character of the classic 911 while delivering modern drivability. However, finding the right parts for this specific build can be challenging. This article breaks down every component you need, common pitfalls, and where to source quality parts.
What Is a Short Stroke 3.2 Engine?
The term "short stroke" refers to an engine with a shorter piston stroke relative to its bore diameter. In the context of a 1977 Porsche, the short stroke 3.2 uses components from two different eras:
- Crankshaft: From the 1977 2.7L engine (70.4mm stroke)
- Pistons and Cylinders: From the 1984–1989 3.2L Carrera engine (95mm bore)
This combination yields a displacement of approximately 3.0 liters (exactly 2,994 cc). The shorter stroke reduces piston speed, allowing higher RPMs without excessive wear, while the larger bore increases valve area for better breathing. The result is a engine that revs willingly to 7,000+ RPM and produces around 200–220 hp (depending on cam selection and tuning).
Why Choose This Build?
- High RPM capabilities: The short stroke design reduces inertial forces, making it ideal for spirited driving and track use.
- Retains classic character: It’s a period-correct upgrade that doesn’t require major chassis modifications.
- Parts availability: Most 3.2L components are still available from suppliers, and the 2.7L crank is common.
Key Parts for a 1977 Porsche Short Stroke 3.2
Building this engine requires a mix of new and rebuilt parts. Below is a detailed list of everything you will need, with specifications and sourcing tips.
Pistons and Cylinders
The core of the build is a set of 95mm pistons and cylinders from a 3.2L Carrera (part numbers 930.101.907.0x for cylinders, and 930.101.901.0x for pistons). These are typically cast Mahle units. For performance builds, consider:
- JE or Ross forged pistons (if higher compression or boost is planned)
- Nikasil or cast iron cylinders (Nikasil is more durable but requires specific rings)
Ensure the piston pin height matches the 2.7L rod length. The 3.2L pistons are designed for 127mm rods, while the 2.7L uses 127mm rods as well—so they are compatible. However, the compression ratio will change. Stock 3.2L pistons with a flat top yield about 9.5:1 with the 70.4mm stroke. Higher compression pistons (e.g., 10.5:1) are available for more power but require premium fuel.
Crankshaft and Rods
Crankshaft: The original 1977 2.7L forged crankshaft (82mm main bearing journals) is used. These are robust and can handle the 3.0L displacement. However, have it crack-tested and polished before reassembly. If the crank is damaged, replacements are available from Porsche Classic or aftermarket like Scat.
Connecting Rods: You will need rods designed for 127mm center-to-center length with a 22mm wrist pin. The stock 2.7L rods are adequate for street use, but for high RPM durability, upgrade to forged aftermarket rods (e.g., Carillo, Pauter, or Arrow). They reduce reciprocating weight and increase strength.
Piston Rings and Bearings
Piston rings must match the cylinder type. For Mahle cast iron cylinders, use Mahle rings (part number 930.101.915.00). For Nikasil cylinders, use moly-coated rings. Avoid mixing ring types for different bore surfaces.
Main and rod bearings are the same as the 2.7L (since the crank and block are unchanged). Use Glyco or King bearings. Ensure correct oil clearance; plastigauge is essential.
Gasket Set and Seals
Complete gasket set for a 1977 2.7L engine (top-end and bottom-end). However, the head gaskets will be for 95mm bore, which are different from the original 90mm. Use 3.2L head gaskets (Elring or Victor Reinz). Also, the intake manifold gaskets may differ if using 3.2L intake ports; verify compatibility.
Cylinder Head and Valvetrain
The cylinder heads from the 1977 2.7L have 34mm intake and 30mm exhaust valves. For a short stroke 3.2, these heads will bolt onto the 95mm cylinders, but the ports and valves are smaller than the 3.2L heads. This can restrict flow above 6,000 RPM. Options:
- Port and polish the existing heads to match 3.2L flow
- Install larger valves (36mm intake, 32mm exhaust) if budget allows
- Use 3.2L heads if you have them—they require modifications to the 1977 engine tins and oil cooler lines
Valve springs should be upgraded for higher RPM (e.g., dual springs from a 3.2L or aftermarket). Camshaft choice is critical: the stock 2.7L cam (DC15) is mild. For the short stroke, a DC17 or grind from Elgin or Web Cam offers a nice balance.
Oil System
The 1977 2.7L uses a non-stacked oil pump. For sustained high RPM, upgrade to the 3.2L oil pump (which flows more) and a front oil cooler. The 3.2L pump fits the 1977 block with minor modifications (swap the drive shaft). Also consider a larger sump or oil pan baffles.
Intake and Exhaust
- Intake: The 1977 2.7L uses CIS fuel injection with a large airbox. For the short stroke 3.2, the CIS system can be retained with larger injectors and a fuel pressure regulator. Alternatively, switch to PMO carburetors or ITBs for better performance.
- Exhaust: Use 1977 exhaust headers (they fit the head stud pattern). A free-flowing muffler (e.g., M&K, Bursch) improves power.
Sourcing Parts: What to Know
While this article does not endorse specific sellers, here are practical tips:
- Pelican Parts, Sierra Madre Collection, and Porsche Classic are reliable for OEM-style parts.
- For performance pistons, JE or Ross are custom-order; expect 4–6 weeks lead time.
- Secondhand 3.2L cylinders are common but inspect for scoring or worn plating.
- Avoid cheap eBay gasket sets; stick to Elring or Victor Reinz.
Common Pitfalls and Mistakes
- Wrong piston pin height: 3.2L pistons have a pin height of 34mm; verify with your rods. If using aftermarket rods, specify 22mm pin.
- Incorrect head gasket bore: The 2.7L head gasket won't fit 95mm cylinders. Use 3.2L gaskets.
- Ignoring oil system: Stock 2.7L oil pump is marginal for sustained high RPM; upgrade.
- Cam timing: The 2.7L cam sprocket is different from 3.2L. Retime carefully; degreed cam helps.
- Balancing: The 2.7L crank is externally balanced with a flywheel and pulley. If using a lightweight flywheel, rebalance.
Final Recommendation
For a 1977 Porsche 911 owner seeking a reliable, high-revving street or track engine, the short stroke 3.2 conversion is an excellent choice. Focus on sourcing quality pistons and cylinders (new or low-mile used), upgrade the rods and oil pump, and match the cam to your driving style. Budget approximately $5,000–$8,000 for parts alone, with another $3,000–$5,000 for machine work and assembly. Consult with a trusted Porsche engine builder to ensure proper clearances and tuning. With careful planning, this engine will transform your 911 without losing its classic soul.