Engine Swap/Conversions FAQ Options

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What conversions have been done?

In many ways, the 914 has traditionally been a hot rodder's car. The chassis is far more capable than any of the engines the factory provided, and for many years, the cars have been inexpensive used. This has lead to a wild array of engine combinations, spawning an entire cottage industry in creating 914 "hybrids".

The most commonly done are Six conversions (911 engine) and Chevy V8s, though Subaru fours are gaining fast in popularity. The Mazda rotary, Chevy V6, Buick V6, and Nissan V6 have also been done more than a few times. The Porsche 928 V8 has been done at least twice, but is very difficult and requires a huge effort to make work. The earliest known swap was a Wankel rotary, which was presented as a gift to Felix Wankel himself.

914club member neo914-6 maintains a list of all known engine conversions.

What about other Porsche engines?

The 944 engine has been mentioned, but it's not known if anyone has managed to make it work. This engine is very long, and won't fit without heavy modifications to the firewall.

Will I kill the transaxle?

The 914 transaxle has been known to hold together up to around 200ft/lbs of torque. It's basically torque that kills transaxles, not so much horsepower. Certainly, the factory themselves used the 901 (the 911 gearbox the 914 gearbox is based on) on race engines up over 200hp. There are also billet intermediate plates (which hold the major bearings) that help a bit more. Both the 915 and the 930 Porsche transaxles have been adapted to the 914 to handle more power. Both are fairly expensive to buy and convert. WEVO makes a shift linkage conversion for the 915 for a very high price. Cable shifters have been fabricated for both. The four-speed 930 seems to be able to handle even a pretty hot V8 without blowing up.

Are there any suppliers of kits and parts?

Yes. Kennedy Engineered Products (aka KEP) provide adapter plates to bolt a wide variety of engines to the 914 transaxle. They also supply flywheels and clutches. They can be found here.

Renegade Hybrids specializes in conversions for several Porsche models. They provide a drop-in radiator kit for any water-cooled engine swap into a 914 that's generally regarded as the best available. They also provide complete kits for Chevy V8 and Subaru installations into a 914.

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What's involved in doing a Six conversion?

The Six conversion is popular since it's a Porsche engine, and since the factory did this themselves. No radiator is required, and all of the parts to do the conversion are available off the shelf, so little to no fabrication is required to make this swap. However, it's far from inexpensive as conversions go, since the engines are not particularly cheap, and very expensive to rebuild.

What engine do I want to use?

The first thing you need to do is buy a copy of Bruce Anderson's book The 911 Performance Handbook, which will give you a complete overview of all of the 911 engines available, and will tell you everything you need to know when shopping for a 911 engine, or considering modifications to one. The original 914/6 used the 1969 911T engine, which was a 2.0L engine using a pair of triple-throat Zenith carbs, rated at 110hp.

All of the aircooled 911 engines have been used for swaps, right up to the 3.6 found in the 964. The 3.6 taxes the 914 gearbox to the limit, however. I don't know of anyone successfully using a watercooled 911 or Boxster engine, yet. These engines are too wide to fit between the suspension ears, so a complete rear suspension redesign and fabrication would be required to effect this swap. People are working on this.

The 915 and 930 gearboxes have been adapted to the 914 for more powerful engines. Based on general experience, the 914 transaxle is adequate at least up to the 2.7, and has been used successfully with 3.0 and 3.2 engines, as well, as long as they aren't abused.

Many people use carbs when making this swap, usually Webers or PMOs. Stock fuel injection can be used (MFI, K-Jet/CIS, or Motronic/DME). At least up to the 3.2, no cutting of the trunk will be required to fit these injection systems. The 3.6 may require some rear trunk modifying to fit it's injection system. The engine lid rain tray will have to go, and the lid latch will have to be relocated or removed in many cases.

What parts do I need?

Besides the engine, you'll need the following:

An engine mount - the type that bolt/weld to the firewall are best. There are several types available, from Patrick Motorsports to Rich Johnson to clones. There are mounts available that use the /4 mounting points, but quality is very iffy and breakages have been reported with disturbing frequency. The firewall mount is less in the way, and stronger.

A flywheel - all 911 engines other than the 2.0 will need to swap the 911 flywheel for the cup-type flywheel used on the 2.0 if you're going to use the 914 transaxle. All of the engines up to and including the '77 2.7 will accept the early flywheel unmodified. The '78 3.0 and later engines all use a 9-bolt flywheel flange in place of the earlier 6-bolt, so a modified flywheel will be required. Kennedy Engineered Products is the most common supplier for this part. You'll also likely need a new clutch and pressure plate.

An oil tank - the 911 engine is a dry sump unit, so the oil is contained in a remote tank. The 914/6 used a tank that mounts in the driver's side fender, and OEM tanks are still available here and there. There are also several reproduction tanks that mount in the same place, of varying quality. Note that the oil tanks by themselves require a filler neck (which also includes the dipstick), and an oil filter console (to attach the filter to the tank). The tank fits between the outer and inner fender skins, and holes need to be cut on the inner fender where those stamped circles are near the relay board.

Racing oil tanks are also commonly used, most often mounted in the front trunk. A tank that is properly baffled to separate the air and the oil and holds at least 9 quarts is required.

Oil lines - to connect the oil tank to the engine. The engine fittings are 30mm metric fittings, and you can buy OEM lines (or reproductions) that have these fittings. You can also buy lines that use AN style fittings, often matched with oil tanks that use AN fittings. Adapters are readily available to connect 30mm metric to AN fittings, using the -12 and -16 sizes. Usually, -12 is used as the high pressure line (scavenge pump to tank), and -16 as the return line (tank to oil cooler).

A line under the oil cooler is where the oil returns from the tank to the engine. The stock 911 fitting (a simple hose barb) can't be used, as it will interfere with the rear suspension. There are several ways to modify this to work, from turning the hose barb into a 90 degree AN-16 fitting, to cutting the undercooler line to have a fitting welded on.

914/6 style engine tin is required to seal the gaps between the engine and the engine bay. This is available in steel, aluminum, and fiberglass.

An exhaust system will be required, as the 911 exhaust points the wrong way. Headers (no heat) or heat exchangers are available in mild steel or stainless. Real 914/6 HEs can be found used, but aren't cheap. A 911 muffler can be used on most of these exhausts.

With a side-shift transaxle, you'll very likely need to modify the shift linkage to clear the exhaust. The stock 914 rear linkage bar is bowed substantially to clear the 914 heat exchangers. The 914/6 bar needs to be much straighter. Simply replacing the bowed section by welding in a straight tube of the same length is usually sufficient.

Other parts depend on which engine you use and what you intend to use the car for. An engine with CIS will require a high-pressure (150psi) fuel pump. A Motronic/DME engine MIGHT be able to use the 914 fuel injection pump. You may need an external oil cooler, esp. on the later, bigger, more powerful engines. For regular track use, even a nearly stock 2.0 may need an oil cooler. For road or autocross use, you may be able to get away without an external oil cooler on anything smaller than a 3.0.

How much does this cost?

(NOTE: prices age quickly, so view this as a rough guide)

Engines prices vary based on age, performance, and completeness. Figure about $1,500 for a bare engine that needs a rebuild (and budget $8-12K for a rebuild), about $3,000 for a decent 2.4 or 2.7, $4-5K for a workable 3.0, and $5-6K for a 3.2. I have no data for 3.6 prices, but they'll be expensive.

Exhausts start at $350 for Bursch mild steel headers and top out at nearly $2000 for stainless heat exchangers.

Oil tanks, lines, and fittings are expensive. A new OEM 914/6 tank is pretty close to $1,000 now, without a filler neck or oil console. Used tanks are usually $400 or more, and will require a good steam cleaning. The DWDesign aluminum tank (a nice reproduction that also holds more oil) is about $750. Filler necks are around $150 new, and oil consoles from $80-125 new. OEM style oil lines are about $300-400 a set. A complete set of AN fittings, adapters, and bare stainless -12 and -16 hose you assemble yourself runs about $300 (add another $300 plus the price of a cooler if you intend to fit a front-mounted oil cooler).

The usual charge to modify the oil cooler is about $150.

A NOS 914/6 flywheel is just under $400, when you can find them.

A Rich Johnson firewall engine mount is $500, more or less.

Figure a reasonable minimum of $8,000 if you get lucky in your choice of engines and can do most or all of the work yourself. Plan on spending at least $10,000. It is possible to do it for less if you get several excellent deals on the expensive parts, but even a bargain basement job is going to cost $4-5K all told.