Porsche 911 3.2L Carrera Air-Cooled Engine (930/921 M298)

The 3.2 Carrera, sold in the USA from 1984 to 1989, is powered by a 3.2L version of the classic air-cooled 911 engine. Officially designated as the 930/21, it's a lower compression, lower horsepower version supplied with an exhaust catalyst known internally as option M298, which is friendly with USA emissions requirements. It was also sold in selected markets globally, including Canada and Japan. Other versions designed for use in Europe and other markets are often called ROW (Rest of World) and feature a few mechanical differences. They're sometimes found inside the USA market, typically by gray market import of the engine or entire vehicle. These are designated 930/20, feature a higher compression ratio, and produce 230hp.

Porsche increased the displacement to 3163cc by increasing the stroke to 74.4mm and the bore to 95mm. Being over-square, with a larger bore than stroke, the 3.2 Carrera engine is most efficient at higher RPM, befitting the sporty nature of the car and Porsche in general. Aside from the larger displacement, mechanically, the 3.2 liter 930.21 engine is simply an evolution of the ‘classic’ air-cooled 911 engine.

The most significant changes to the 3.2 Carrera engine over the 3.0L it replaced are the fuel injection and engine management. Featuring a Bosch Motronic 2 DME engine management system and Bosch’s new LE-Jetronic fuel injection, the 3.2 Carrera saw increases in both power and efficiency over the outgoing Bosch CIS K-Jetronic mechanical fuel injection used on the 911 SC. 

The Bosch Motronic 2 engine management system was also the first of its kind to allow for easy ‘chip’ tuning via a programmable and removal EPROM ‘chip’ – opening new doors for tuning and modifications. 

Learn More About The Air-Cooled Porsche 911 Here

Porsche 911 3.2 Carrera 930/921 M298 Engine Fluids

Engine	Engine Oil Type 20W-50 Engine Oil Capacity 10 Liters Service Fill | 13 Liters Dry Fill Porsche Engine Oil Change Kit (20W-50) - Liqui Moly LM22072KT3 SKU: KIT-LM22072KT3 View Product QTY $81.05+
Manual Transmission(Without Limited Slip Differential)	Manual Transmission Fluid Type API GL5 75w90 Manual Transmission Fluid Capacity 3 Liters 75W90 Fully Synthetic Hypoid Gear Oil (1 Liter) - Liqui Moly LM22090 SKU: MOL-LM22090 View Product QTY $18.09+
Manual Transmission(With Limited Slip Differential)	Manual Transmission Fluid Type API GL5 75w90 Manual Transmission Fluid Capacity 3 Liters Gear 300 LS 75W90 Gear Oil (1 Liter) - Motul 105778 SKU: MTL-105778 View Product QTY $25.59+

Decoding Porsche 3.2L Air-Cooled Engine Serial Numbers

The 930/21 can be identified by an 8-digit alphanumeric serial number, as follows. 

• Unit type (number of Cylinders) 

• Engine type (specification)

  • 3 = ROW

  • 4 = USA M298/ROW

• Year

  • E = 1984

  • F = 1985

  • G = 1986

  • H = 1987

  • J = 1988

  • K = 1989

• Serial number (remaining 5 digits)

The engine serial number appears at the vertical base of the fan casting on the right side of the engine.

Decoding the following engine serial number, 64J043874—we can deduce that it’s a 6-cylinder, M298 USA/ROW engine from 1988, serial number 04387. 

Engine Speed Sensor

The 3.2 Carrera marked a major departure from previous Porsche 911s, such as the outgoing 911 SC with the Bosch LE-Jetronic fuel electronic fuel injection system, a major departure from the previous Bosch CIS injection system, which used a mechanical, pressure-based injector. The Bosch Motronic 2 DME was also new and uses an engine crankshaft position sensor, also known as an engine speed sensor, to tell the DME what the RPM of the engine is, or indeed if it is running at all. 

The engine speed sensor is quite simple - it reads the ‘teeth’ on the trigger wheel via a small magnet, and the electromagnetic signal that is generated is sent to the DME, where the DME makes adjustments for fueling and timing based on the RPM of the engine, throttle position, intake airflow, temperatures, and other factors. If the engine speed sensor is bad or failing, it will send no signal or an incorrect signal to the DME. If this happens, the engine may stumble, run poorly, or not run at all, as the DME cannot safely determine engine speed. 

Because the engine speed sensor is electromagnetic, it has a specific electrical resistance range that is in the “safe” or acceptable range. Once it is out of that range, the DME can no longer read it. Heat is one of the largest contributing factors to the engine speed sensor reading outside of the range, and a bad or failing ending speed sensor may first start to show problems in very hot weather, after running for extended periods, or both. 

The electrical connectors are also typically brittle and easily broken, so if you are servicing the engine wiring for any reason, and the engine speed sensor on your 3.2 Carrera is of unknown age, or the connectors are broken, a preventative replacement can help to avoid a roadside break down. If your 3.2 Carrera won’t start and is otherwise running fine, checking the resistance on the engine speed sensor is a good place to start. It should be between 600-1600 ohms, hot or cold. Anything outside of that range and it should be replaced. 

Engine Oil Leaks

The 3.2 Carrera, being an evolution of the classic air-cooled 911 flat-six engine, suffers from many of the same or similar faults and common oil leaks as previous versions. Some of the most common are oil leaks and seeps from the oil return tubes, timing chain box gaskets, and the aptly nick-named ‘triangle of death.’

The oil return tubes are quite common and, thankfully, fairly easy to replace. They can be replaced in cars without any engine disassembly. The oil return tubes run from the cylinder heads to the engine crankcase, have an o-ring at either end and allow engine oil to drain back from the sides (heads) to the center (crankcase) of the engine. These o-rings become old, dry out, shrink, and harden, and are a common cause of oil leaks. New, two-piece return tubes can be installed in place of the original 1-piece units once they’ve been cut out and are a simple fix for a common 911 engine oil leak issue. 

The 3.2 Carrera chain box gaskets are a simple but large composite material gasket that seals the timing chain cover to the engine crankcase. These will leak over time as the gasket material ages and goes through heat cycles, and the gasket deteriorates due to oil exposure. This is also one of the lowest points on the engine, meaning that there is more or less always engine oil sitting on the gasket, and so it’s a common leak. All the old gasket material should be removed before the new gaskets are installed, otherwise the leak will return more or less immediately because of the low amount of crush and tight tolerances of the chain box cover to crankcase fitment. 

The Triangle of Death, as it is often called, consists of multiple oil leak locations that are on the top side of the engine and can often lead to misdiagnosis or, at the very least, mystery oil leaks after you’ve taken care of the other common locations. The triangle of death is made up of the oil pressure switch, the crankcase breather gasket, and the oil thermostat o-ring and is located at the top rear of the engine, towards the transmission side. Of these, the oil pressure switch and oil thermostat o-ring can easily develop into substantial leaks because they are both high temperature and high pressure. If you’re experiencing oil leaks and have addressed some of the other common items, checking the triangle of death could be a good next step.  

Engine Oil Lines

Since the Porsche air-cooled engine relies largely on oil to help keep things cool, moving that oil from the engine, to the tank, and various coolers is a large task, and one that requires a number of hoses, fittings, and lines to get it all done. The 3.2 Carrera has two that are particularly troublesome once they begin to leak. 

The “S” Hose, which is the oil cooler to oil tank supply line, is a common leaking point because, unlike many of the other hoses and lines, this is a simple slip-fit line made of rubber. Because of this, it is common to leak at either hose end as the rubber ages, hardens, and dry rots. If it fails completely, it is not only very messy, but as the supply of engine oil to the oil pump, it can mean significant engine damage if it does. It’s held in place by two simple clamps, which you may want to also replace while you have the line off. It’s best to do this during an oil change as well. 

The camshaft to case oil line is one of those formed high-pressure lines, and so when it leaks, it typically will start to cause more of a mess as it gets worse. The cam-to-case oil line has a banjo end with two crush rings that can leak, but more likely, the rubber-to-steel crimp fittings will leak more often. A gasketless male/female threaded connection to the chain tensioner also exists. If in doubt, replacing both of these lines can be helpful, but having no rubber connections, the chain tensioner line is less likely to leak unless the threads or sealing surface is damaged, causing a leak. 

Engine Alternator

Just as with any modern vehicle, the engine alternator is a crucial part of the electrical charging system of the 911 3.2 Carrera. Unlike most other modern vehicles, the alternator on the 3.2 Carrera, and indeed most other air-cooled Porsche 911s, is an integral part of the cooling system as well. The engine cooling fan attaches to and is driven by the alternator, so aside from charging the battery, it is part of the primary cooling as well. 

An engine alternator can fail electrically or mechanically. The voltage regulator, the device responsible for the charging output to the battery, can over or undercharge the battery, or the brushes and other electrical components that generate electricity can wear to the point of no longer functioning correctly. Mechanically, the bearings can fail, leading to noise, play in the shaft, and damage to the alternator or even possibly the engine cooling fan. If the alternator output is not in spec, it is common to see the ‘dummy light’ for the engine battery to flicker when running as an indicator that further diagnostic and a replacement may be needed.

It’s also very common for the engine cooling fan to have cracks or fatigue in the blades, so be sure to inspect this closely and purchase a new fan if needed. A kit that includes all the needed hardware, a belt, and shims is going to be the best choice for tackling this job with everything you will need on hand. 

Fuel Pump

The 3.2 Carrera relies on a variation of the classic, tried-and-true, high-volume high-pressure Bosch fuel pump that has fed fuel to countless European cars over the years. This one fits mid-80s Porsche 911, 944, 944 Turbo, and 924S models. Fuel pumps can lead a hard life, especially if the car sits for extended periods or has recently come out of storage. It is not uncommon for the fuel pump to work well enough for the car to still run and drive fairly close to normal until total failure. You may experience some minor changes in how quickly the car will start from cold, the idle quality, and how smoothly the engine runs, but as these changes are both minor and happen over time, you may not notice right away. 

Once the pump fails completely, it will typically lock up and produce zero fuel pressure, and the engine will not start. This can happen seemingly out of nowhere and can even be intermittent at times. Because the fuel pump is gravity-fed from the fuel tank on the 3.2 Carrera, running the car out of fuel is one of the most common ways to shorten the life of the pump or cause a failure. Because the fuel flowing through the pump helps to cool the electric motor, if it runs dry, the pump can overheat and damage the pump or motor, which will eventually seize. 

The fuel pump is located under a protective cover at the front of the car and is easily accessed once it is removed. The original fuel pump is blue in color, and if your 3.2 Carrera has this, you should replace it immediately as it is a question of when, not if, it will fail in the near future. It’s also best to replace the feed line at the same time, as this is often beginning to harden and crack and can eventually cause a fuel leak. 

Replacing the in-tank fuel pump strainer is also a good idea when replacing the fuel pump, but keep in mind you will need to fully drain the tank to do this, so be sure to have appropriate storage for the fuel that is drained. So if your fuel tank is full, you may want to wait until you’ve run the rank a bit lower in order to safely capture what is inside. 

Engine Mounts

The 3.2 Carrera, like all previous air-cooled Porsche 911s, has a deceptively simple setup when it comes to engine mounts. There are two, along with a single transmission mount, and together, they support and locate the entirety of the drivetrain of the car. They are located at the outer left and right sides of the engine bay, at the rear of the car, while the transmission mount is centrally located towards the front of the car, at the back of the transmission.

The engine mounts are made from rubber, dampening vibration from the engine and keeping it from causing noise or vibration in the cabin. They also control the weight and movement of the engine under acceleration, braking, and cornering, so they have a big job to do and are fairly small and simple units. 

A bad engine mount or mounts will be most obvious by a few symptoms. First, the gear lever may move front or rearward under hard acceleration or braking, or it may be hard to shift or find gears through corners. This is caused by a misalignment of the shift rod and the transmission itself. You may also feel the engine moving around or throwing the balance of the car off under sharp throttle or brake transitions. 

Porsche 911 engine mounts will slowly degrade over time as the rubber begins to harden, crack, and compress, allowing for excess driveline movement. Replacement is fairly easy, and the standard replacement parts are inexpensive. You can also opt to swap from the factory rubber to a higher durometer (more firm) Powerflex polyurethane compound. This will limit driveline movement more than stock, providing sharper response and more predictable weight transfer, and better control of engine movement. It may also transfer a bit more vibration into the cabin at idle, but this is usually minimal. 

Debris Between Engine Fan Shroud & Cyliner Heads

Like most cars, the 3.2 Carrera’s warm engine bay can make for an attractive nesting spot in the winter time for various small creatures that may be looking for a way to get out of the elements. The design of the engine cover and shroud and the space between it and the cylinder heads of a flat, air-cooled 911 engine, make an even more attractive spot than most. 

Any air-cooled 911 that sits for extended time periods outdoors or even in most garages, and especially one that has been sitting for months or even years, should periodically have the engine checked for animal nests. They tend to build nests towards the rear of the engine, and all this dirt and debris, and nest materials will reduce and restrict airflow across the cylinder heads. This can lead to uneven cylinder cooling, higher cylinder head temps, and significant damage in some cases. 

You’ll need to remove the engine cover air shroud to fully remove any debris. A combination of air, water, and degreaser/cleaner is usually helpful to getting all of it out and restoring airflow through the cylinder head fins. 

Cylinder Head Temperature Sensor

The cylinder head temperature sensor of the 3.2 Carrera is a critical part of the fuel system, as it feeds engine temperature to the DME, which it uses to adjust air-fuel ratios. An engine needs significantly different amounts of fuel based on engine temperature, load, and other conditions. This is especially true at a cold start when it needs the most fuel to the fire and run until it is warmed up. 

While the outgoing Bosch CIS systems used a device called a warm-up regulator to adjust air fuel when cold or hot, the Bosch LE-Jetronic uses this cylinder head temperature sensor, located on cylinder #3, to do the same. Just like the engine speed sensor, this has a resistance range and should read between 1000-2000 ohms. 

If the cylinder head temperature sensor fails, you may notice your 3.2 Carrera is hard to start, runs rough, or may have a no-start situation, just like a bad engine speed sensor. Also just like any other plastic connectors in the engine bay, this one is particularly fragile as it ages and will frequently break apart and crank when touched or removed. 

Cylinder Head Studs

One of the most common issues on both the 3.0 911 SC and 3.2 Carrera is broken head studs. It’s often one of the first things that should be checked on a pre-purchase inspection, and depending on how many, if any, are broken, it’s a good indication of how soon the engine will need to come out for replacements. Depending on the mileage and condition of the engine and what you chose to address while replacing the broken studs, this could be considered a “top-end rebuild,” which can get rather expensive. 

Porsche air-cooled engines are very modular in terms of how they are assembled. There is a main crankcase that has two halves, which houses the crankshaft, and each cylinder is assembled from that. There is a cylinder sleeve and a cylinder head for each piston and rod assembly, and each of those has four cylinder head studs. The studs keep the head and cylinder tightly sealed to the case and ensure proper engine performance and keep gaskets and seals tight. 

The bottom side cylinder head studs are the ones that will break, primarily due to fatigue from heat cycling and corrosion. They are made of a material called Dilavar and are more susceptible to breaking than steel studs. There are many opinions on what is or isn’t safe as far as continuing to drive a 911 with broken cylinder head studs. One broken stud on a cylinder is enough to cause engine oil leaks and adds additional strain on the remaining studs. If you have one to two broken cylinder head studs on different cylinders, it is generally safe to continue driving the car but plan for an engine-out replacement in the future. If you have two broken cylinder head studs on the same cylinder, you should not drive or operate the engine until they are replaced. 

Replacing broken cylinder head studs will require removing the engine and, at minimum, removing the cylinder heads to replace the studs. Before removing the engine, you should perform a compression and leakdown test to check the condition of the piston rings, cylinders, and valves/ seals. If everything looks good and is within spec, you could get away with replacing gaskets and studs only. However, it is generally best practice to have the heads sent out for new valve guides and seals and to have a valve job performed. With the mileage on these cars and the work it takes to get to the point of replacing studs, it makes the most sense to do all the work you can at that time, even if it will cost a good deal more. 

Upgraded cylinder head studs from Raceware are available, and although they will cost more money, they do provide extra piece of mind in ultra high performance and race applications. The best OE option is to replace all 24 studs with steel versions, as linked below.

Intake Manifold Gaskets and Flanges

The intake manifold gaskets on the 3.2 Carrera are another common area that will need attention if they have not yet been replaced. The combination of heat and age, plus the likelihood of oil contamination from any top-side leaks, means that the gaskets and flanges can degrade over time. When this happens, a minor to major air intake leak can develop, causing a variety of issues. Rough running and misfires are the most common problems, but as the flange continues to fall apart, it can develop into more substantial running problems or total loss of cylinder function. 

Any unmetered air entering the engine will throw off air-fuel ratios, effecting power and efficiency of the engine. Additionally, this can allow gasket or flange material, as well as other dirt and debris into the engine, potentially causing more serious problems and engine damage down the road.

Thankfully, these are inexpensive parts, so if you are unsure of the age and condition of your current 3.2 Carrera intake manifold flanges and gaskets, they are ideal parts to replace proactively before they become a problem. You will need 6 flanges and 12 gaskets per vehicle.

Throttle Position Sensor (Idle Switch & Full Throttle Switch)

The throttle position sensors on the 3.2 Carrera 911 feed information to the DME to let it know what state of operation the engine is in, and it then makes adjustments to tune and operation as needed. It’s actually two different microswitches versus what you may more commonly think of on a modern vehicle, which is a potentiometer with a fine range of throttle positions fed to the DME from idle to full throttle. 

The 3.2 Carrera has an idle switch, and at idle position or throttle closed, the DME will make changes and adjustments that impact engine idle speed and deceleration. At full throttle, the DME switches to a closed-loop operation, ignoring feedback from the oxygen sensor and optimizing for performance and horsepower. In the middle, i.e., not at idle or full throttle, the DME interprets information from the O2 sensor along with engine speed and optimizes for fuel efficiency and emissions. 

If the idle position sensor on your 3.2 Carrera goes bad, you may notice a high idle or a tendency to have extended “rev hang” shifting between gears. That is because they tend to fail in the open state, and the DME does not “see” that the throttle is closed and doesn't make the changes to return to a normal idle state. Likewise, at full throttle, if your full throttle switch is bad, the DME will not go into closed loop mode, and it may not make full power, as it will still be looking at information from the O2 sensor and working towards efficiency versus horsepower. 

Performance Exhaust

It’s hard to narrow it down to just one classic trait that makes the 3.2 Carrera such a classic, but the air-cooled flat-six engine and its distinct engine tone definitely rank near the top. The factory exhaust from Porsche works well, but providing a little more airflow for the 3.2 L flat-six not only helps make more power but also uncorks a little more of that classic Porsche sound. While power gains will not be enormous, every bit helps, especially on a car as light as the 3.2 Carrera.

The best option will be to pair a performance muffler with a set of Dansk/SSI header heat exchanger units. It’ll provide a perfect match between the components and the best sound and performance. 

Lightweight Flywheel & Performance Clutch

While adding more horsepower to your 3.2 Carrera may be a challenge beyond a few simple bolt-on parts, upgrading to a lightweight flywheel and performance clutch will go a long way toward making sure more of that power gets to the ground. The 3.2’s OE flywheel is reasonably light at around 11 lbs. A lightweight billet steel flywheel from AASCO Motorsports will shave a couple of lbs while still providing the durability of steel. 

Paired with a Sachs Performance clutch, you will have a reliable, high-quality performance option close to the factory feel but with a more responsive engine. The reduced weight allows for better engine response, especially in lower gears, such as when accelerating away from a light or out of a corner. The only downside could be a slight change in the amount of throttle needed when engaging from a stop, along with an occasional increase in noise from the clutch assembly. This is usually minimal with a steel flywheel and within owners’ acceptable limits. 

DME ‘Chip’ Tuning

Aside from the improved power and efficiency of the Bosch Motronic 2 DME engine management system and Bosch LE-Jetronic fuel injection of the 3.2 Carrera, there is an added benefit of more flexible performance tuning. The DME unit has a removable EPROM, more often called a chip, and it can be removed and swapped for one optimized for more power, torque, and responsiveness. Anything from an off-the-shelf baseline tune to a custom one that accounts for specific modifications is available from several aftermarket tuners, such as Cargraphic, Fabspeed, and others. 

Performance gains will vary depending on other modifications, engine condition, fuel, and atmospheric conditions. Still, gains of 15-20 horsepower are possible with no other changes, with slightly lower gains in engine torque. 

Porsche 3.2L Carrera Models, Production, & Model Years

3.2 Carrera Models:

• Coupe
• Targe
• Convertible
• Speedster,
• Club Sport

3.2 Carrera Model Years:

• 1984-1989

Porsche 3.2L Carrera 930/921 M298 Engine Specifications

• Horsepower: 207hp (1984-1986), 217hp (1987-1989)

• Torque: 192 lb-ft tq (1984-1986), 195 lb-ft tq (1987-1989)

• Bore - 95mm

• Stroke - 74.4mm

• Compression Ratio - 9.5:1

• Fuel injection type - Electronic, Bosch LE-Jetronic

• Engine Control -  Bosch Motronic 2

• Aspiration - Atmospheric

• Engine Redline: 6,250 rpm

• Lubrication - Dry sump w/ oil tank

• Materials

  • Engine Case - Aluminum 

  • Crankshaft - Steel (forged - Tenifer treated) 

  • Connecting rods - Steel (forged) 

  • Pistons - Alloy (Forged Mahle)

  • Cylinders - Aluminum (Nikasil Coated, Mahle)

  • Cylinder Heads - Light Alloy Aluminum

Porsche 3.2L Carrera Club Sport 930/920 M637 Engine Specifications

The extremely rare 3.2 Carrera Club Sport featured a blueprinted and lightly tweaked 3.2Lengine, mated to a short-ratio G50 gearbox. Known internally as option M637, Porsche built only 28 examples for the USA. The ROW 3.2 Carrera Club Sport maintained the same engine serial number coding and specifications as the standard 3.2 Carrera ROW 930/20 but should be stamped “81” on the cylinders and heads. Interestingly, despite the internal modifications, Porsche did not rate the M637 Club Sport at a higher horsepower or torque rating than any other 930/20 engine. 

Unfortunately, the USA version 3.2 Carrera Clubsport featured the standard 930/21 engine.

• Horsepower: 207hp (1984-1986), 217hp (1987-1989)

• Torque: 192 lb-ft tq (1984-1986), 195 lb-ft tq (1987-1989)

• Bore - 95mm

• Stroke - 74.4mm

• Compression Ratio - 9.5:1

• Fuel injection type - Electronic, Bosch LE-Jetronic

• Engine Control -  Bosch Motronic 2

• Aspiration - Atmospheric

• Engine Redline: 6,250 rpm

• Lubrication - Dry sump w/ oil tank

• Materials

  • Engine Case - Aluminum 

  • Crankshaft - Steel (forged - Tenifer treated) 

  • Connecting rods - Steel (forged) 

  • Pistons - Alloy (Forged Mahle)

  • Cylinders - Aluminum (Nikasil Coated, Mahle)

  • Cylinder Heads - Light Alloy Aluminum