Engine Swap/Conversions FAQ Options

[lapuwali]

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.

[lapuwali]

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.

[lapuwali]

Subaru conversion

(NOTE: many thanks to Evan Thompson [mongrel-gs] for providing this section).

The Subaru 4 cylinder conversion is popular because of the price, power, and parts availability. A radiator is required for this conversion, but it may be successfully placed in the engine bay or front trunk. There is a kit available for this conversion from Renegade Hybrids, or the cost may be kept down by doing some home fabrication. There will be some cutting of the car involved... if the radiator in put in the front trunk, a venting system will need to be worked out. If the radiator is to be put in the engine bay, removing the front engine shelf is recommended (although many going this route remove all the engine shelf metal, anyway). As far as weight, the 4 cylinder n/a Subaru conversion should weigh the same or maybe even a bit less than the stock type IV engine. Turbo Subaru engines obviously require more plumbing work, and getting everything to fit without cutting the rear trunk floor is very challenging.

Which engine do I want to use?

From the NASIOC forum

EJ18: Found in Imprezas from 1993-1997. Rated at 110hp and 120 ft-lbs
EJ22 Phase I: Found in Legacies from 1990-1998 and Imprezas from 1995-1998. Comes rated at 130hp and 137 ft-lbs, 135hp and 140 ft-lbs, or 137hp and 145 ft-lbs.
EJ22 Phase II: Found in Legacies in 1999 and Imprezas from 1999-2001. Rated at 142hp and 149 ft-lbs.
EJ22-T Phase I: Found in Sport Sedan and Touring Wagons (Legacies) from 1990-1994. Turbocharged and non-intercooled. Rated at 160hp and 181 ft-lbs. Closed deck, cast pistons, forged rods, oil squirters: turbo motor. Poor flowing heads.
EJ25 DOHC Phase I: Found in Legacies from 1996-1999, Imprezas in 1998, and Foresters in 1998. Rated at either 155hp and 140 ft-lbs in 1996 or 165hp and 162 ft-lbs in 1997-1999.
EJ25 SOHC Phase II: Found in Legacies from 2000+, Imprezas from 1999+, and Foresters from 1999+. Rated at 165hp and 166 ft-lbs. There was a slight compression ratio change from 1999-2000 where it went from 9.7:1 to 10.0:1.
USDM EJ20: US Domestic Market WRX. Found in 2002+ WRXs. Rated at 227hp and 217 ft-lbs. Turbocharged, intercooled, open deck, and decent heads.
EJ25T DOHC: Available in 2004 in the Forester XT. Rated at 210hp and 235 ft-lbs. Turbocharged, intercooled, VVTi (Variable Valve Timing), and drive by wire.
EJ25T-STi DOHC: Available in 2004 in the WRX STi. Rated at 300hp and 300 ft-lbs. Turbocharged, intercooled, AVCS (Active Valve Control System), drive by wire, intercooler sprayer, and semi-closed design.
EG33 and EZ30- The six cylinder boxers... it may be possible to fit them in, but the radiator will most likely end up in the front trunk.

Whatever the choice, get as much included with the engine as possible. Longblock, intake, alternator, engine wiring harness, front bulkhead wiring harness, ecu, main and fuel relay, exhaust, engine mount blocks, O2 sensors and harness. Depending on the model, you may need the intake tube and MAF, ignitor on firewall, air pressure sensor. Additional OBD-I and OBD-II codes may be avoided by using all the EVAP solonoids at the gas tank, a sensor simulator from Small Car Performance, or by strategic use of resistors. In the later models(at least the EJ25 SOHC) there is a difference in the manual and automatic transmission engines. Either will work, just make sure you get parts matching the same year, model, and transmission.

What parts do I need?

Besides the engine, you'll need the following:

An ECU- The stock Subaru ecu will work, and will require no dyno tuning time. Additionally, it is possible to make the engine OBD-II compliant, meaning troubleshooting ease with a code scanner. It is also possible to use a Megasquirt system as a controller, and possibly some other commercial systems such as SDS. If you use the stock ecu, it is critical that you match the year, model, transmission, and if possible the vin. Note that most of the later engines have no distributor, nor any provision for one, so converting to carbs and a distributor is not really an option.

An engine mount - Can be purchased in the kit from Renegade Hybrids or fabricated.

A flywheel/adapterplate - Can be purchased in the kit from Renegade Hybrids, or separately from Kennedy Engineered Products to mate the engine to the 901 transmission.

A radiator and mount- A front trunk mounted kit can be purchased in the kit from Renegade Hybrids, or a engine bay mounting frame and ducting can be fabricated for use with a stock Subaru radiator, or an aftermarket radiator such as Koyo.

A air filter- A simple K&N universal filter or the 914 round filter assembly can be adapted.

A oil pan- Although the stock pan can be used, there will be very little ground clearance. The pan can be cut down. Shortened pans are available from many suppliers such as Kennedy, Small Car, Outback Motors, and may be included in the Renegade kit.

A shift linkage- The sideshift shift linkage may need to be cut and rotated 90 degrees, depending on the mount and exhaust designs.

An exhaust system- Can be fabricated by modifying the stock system. Stub pipes are available from Outback Motors.

Assorted bits/pieces/notes/links
Alternator- The top of the alternator bracket shout be cut off and the alternator rotated 180 degrees. A tensioner may be fabricated, or a club member may be producing a very nice bracket system.

Intake manifold- In most cases is rotated 180 degrees to face the front of the engine bay. Stock manifold gaskets can still be used. This provides more rear trunk clearance. Some engines will require this modification, others will not.

Gauges- A water temp and oil pressure gauge are recommended. The oil pressure light sender on the engine can be used for the oil light in the dash.

Tachometer- Early (silver button) 914 tachometers will not register the stock Subaru ecu tach output signal. They can be modified to work with the addition of one resistor (search the forum). Later 914 tachometers should work fine. The basic 5" Autometer tach(~$100) will fit in place of the original tach and register correctly.

Heat- Now that there is some hot water available, any hot rod heater core can be used. These can be found for $100-200, and may be located in/around the engine bay with ductwork routing to the stock hot air ports, or in the front trunk, which may provide more heat. Renegade also sells a heater that replaces the fresh air blower for ~$400.

Renegade Hybrids- http://www.renegadehybrids.com - complete conversion kit, assorted conversion parts
Kennedy Engineering- http://www.kennedyeng.com - adapter plate and flywheel
Small Car Performance- http://www.smallcar.com - assorted conversion parts
Outback Motors- http://www.outbackmotors.com - assorted conversion parts, stub pipes, performance
Cobb Tuning- http://www.cobbtuning.com - performance parts, tuning, high performance heads, etc

How much does this cost?

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

If bought as a package, the original engine and extra bits can be had for under $2K. JDM (Japanese Domestic Market) longblocks can be found on ebay much cheaper, but less complete. Longblocks from salvage yards can be found for between $500-1000. Expect to pay much more for the Sti engine, and beware the possibility that it may have been run hard with little maintainence. It can generally be assumed that these are interference engines, so a timing belt replacement would be wise if the mileage on the engine is > 60,000 miles ($125 in parts), and seals on a stored engine will tend to leak on startup.

Exhaust stubs are ~$250, the remainder of the system can vary greatly.

The Renegade Hybrid kit is $2,000, with an additional $1,000 for the front trunk radiator kit.

A stock radiator should cost around $125.

The Kennedy flywheel and adapter plate is ~$500.

A shortened oil pan will run $250-300.

It is possible to complete a conversion with home fabrication and some good finds for under $2,500. Renegade quotes a complete conversion cost as $7200, without the engine. However, that price does include bits for a turbo setup, heater, carrera suspension, etc. Their basic n/a kit and radiator intallation would come in at $3,000, plus a good deal on an engine and other bits would probably put the price in the $4,000-5,000 range.

[lapuwali]

Chevy V8 conversion

(Many thanks to Felix [neo914-6] for contributing this answer)

What's involved in doing a Small Block Chevy (SBC) V8 conversion?

The SBC V8 conversion is popular since these engines and parts are commonly and economically available, and provide good cost vs. performance compared to the Porsche six or four, as long as you keep it “basic”. Be warned, you can easily build a V8 conversion close to or above the cost of a basic Porsche 6 conversion so the first step is to assess what kind of car that you want, what your time and financial budget will allow, and your true sense of adventure. The GM V8 has been transplanted in thousands of US and European cars so why not the 914? Complete kits are available from Renegade Hybrids, Desert Hybrids, Rod Simpson, and maybe Reddawg [who doesn't have the best repuation here - ed]. For a fee, all but Simpson can build you a turn-key 914. With development since the early 70’s, this is a proven bolt-in conversion and fabrication is minimal. You will lose the front trunk to air management openings for the radiator and you need a some clearancing in the rear trunk for the distributor. This is a major turning point since it ends most chances of returning the car to stock.

What engine do I want to use?

The first thing you need to do is research. Find a conversion on this site (see the non-OEM conversions list) with the engine that you’d most like to copy and research all you can about the challenges and benefits of that particular configuration. You can buy a copy of Ed Ducey’s 914 V8 Conversion Reference (available on eBay or 914club resources) as it’s a small investment in planning your conversion. You can also purchase information from the conversion kit manufacturers but unfortunately they are lacking in technical detail. They offer phone support which isn’t available 24hrs or most weekends so chose your company carefully.

We won’t discuss the modern SBC V8’s (LT, LS) as there are different challenges and very few running examples (though it HAS been done -ed). The basic engine in this conversion is classic 283 to 350cid (4.5 to 5.7L) with 200-300hp. A higher revving engine, with a torque curve higher up the rev range, is recommended to match the engine to the stock 914 transaxle’s short gearing. Built 357 and 383 to 427 (you read that right) have higher HP and torque and will require a stronger transaxle since most who want the high HP want to be able use it. A 400-550 hp built engine with a Porsche 930 or ZF transaxle will match most mid-engine supercar’s power to weight ratio but plan on more structural, brakes, and suspension upgrades to be safe. This will no longer be an economical conversion.

The stock mid-engine 914 ”901” (901 is early 911) transaxle has been successfully used in the basic V8 conversion and is the most cost effective as long as you don’t accelerate quickly from a stop. The first gear is too short so you have effectively 4 speeds. Replacement is still fairly inexpensive, but a stronger 914 transaxle with taller gears and intermediate plate will cost a good bit more. For larger hp engines, both the rear engine 915 5-speed and 930 4-speed gearboxes have been adapted to the 914. While the 915 has a well developed mid-engine shifter by WEVO, this and the costs to flip the R&P gear and rare taller gears for the V8 make the 930 the better choice for strength vs. cost.

What parts do I need and how much does this cost?

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

If you are resourceful or a great bargain hunter you can reduce these costs.

Above all, start with a clean tub or take care of the rust and worn or broken parts first. The biggest complaint with anti-conversion folks is that there are many hack jobs or neglected donor 914s. Many of these become works in progress or development projects. Please don’t misrepresent this conversion. Yes, once you allow yourself to modify the powerplant you there is a trend of modifying the body, the interior, etc. Follow a theme, “sleeper”, race like, or a modern hot rod. Getting out of budget before the conversion is functional gets more expensive in the end and there is a tendency to sell incomplete “projects” for pennies on the dollar.

Engines prices vary based on age, performance, and completeness. Figure about $500 for a complete used running donor engine that needs a $1k rebuild, about $2-5k for a crate engine, and $6-10K for a hand built engine to specs.

Many people use 4 barrel Holley or Edelbrock carburetion ($200) or you can use aftermarket fuel injection (~$1k) and stand alone engine management ($1-1.5k) that allows more tuning and fuel efficiency. A drop-down air cleaner will allow you to close the engine lid. Many use larger air cleaners and run without lids.

The gearbox prices are: $200-400 for a used 914 transaxle, $2500 modified, and $6-8k for a flipped 930 or 915 with shifter. If you find a cheap 930 donor, the modifications will cost ~$4-5k. You will need upgraded $600 axles and CVs, trans cradle mount, $1k cable shifter, and a speedo adapter. Some have flipped the entire 930, (to avoid the R&P flip) which requires $1k oiling system and losing some of the rear trunk.

Starter: high torque 911 or modified compact Mitsubishi $100-250

Wiring is fairly simple especially with one-wire alternators and pointless distributors but pre-modified harness’ are available for ~$200. BTW you should get a pointless distributor because timing marks are difficult to access unless you are under the car with the timing light. There is a technique of marking the flywheel and timing through a small hole in the trunk.

Tachometer: you can make a simple mod or buy a professionally modified tach for ~$100.

For the resourceful builder, you can start with the Kennedy Engineered Products engine adapter, clutch package and starter for $1200. You will need to fabricate the engine and transaxle mounts and buy the water pump. You may be able to fabricate the w/p and alternator bracket if you chose not to buy them.

V8 Conversion Kits are about ~$2k for basic 8” clutch and another $400 with upgraded 9” clutch package. Costs are comparable between the suppliers and designs are similar so look for service or quality. There is a large menu but purchase the complete package to avoid less fabrication and development.

While you only add 2-300 lbs to the overall weight of the car, you will have faster acceleration, which means more momentum to stop. Drive within the capabilities of the stock four wheel disc brakes or upgrade. At a minimum, spend a couple of hundred dollars and refurbish all wear parts on your stock brake system with good pads and synthetic fluid. Minor upgrades are $100 stainless steel lines and $250 19mm master cylinder. Upgrading to 911 front suspension and rear 5 lug including used wheels and new tires can cost upwards of $2-3k. You will need to add 911 ebrake or spot type parking brake. Drilling the rear hubs for 5 lug and keeping the rear brake caliper is a cheaper option. More costs if you get wider wheels which is common on high hp conversions.

Suspension - minimum upgrades are $200 190 lb rear springs to handle the added weight. A larger diameter front sway bar for increased throttle oversteer will cost $250-500. Larger front torsion bars and sport shocks are can be added for another $800, remember these are still Porsche parts.

Radiator – this is one of the most important details of the conversion. The proven cooling system is the $1k radiator made by Ron Davis specifically for Renegade Hybrids. I have seen others that work fine but there is high praise for those who switched to it from other systems. If you want to save money copy one of the non-Renegade cooling system that’s “proven” to work and fabricate the mounts and shroud for ~ $400. There’s no need to experiment with your engines life as overheating is a killer. Add $200 for Green stripe or equivalent radiator lines, fill tank, overflow tank, and hardware.

Water Pump – Most conversions use the custom housed Chrysler impeller available from the kit builders, $350 if sold individually. Replacement impellers are only ~$70 from local auto stores. The w/p must be mounted to the side of the engine unless you are willing to cut the firewall and fabricate a box between the seats. Electric Meiziere water pumps have been used with success.

Shifter bar extended 1” to account for the adapter plate and engine length, 1 hr fabrication rate.

Exhaust systems - can be basic manifolds provided with engine and used mufflers, or $300 in headers and a pair of turbo mufflers, to over $800 for coated headers, custom exhaust cross over tubing, and premium mufflers.

Chassis reinforcement – GT kits are widely available as well as inner “C” from Engman and clamshell long reinforcement. Cages or roll bars are recommended for any high speed car.

Since most kits don't allow use of the mechanical fuel pump, you will need an electric pump and regulator. Many like the Holley Blue rotary type or find another that is relatively quiet and is designed to either push or pull depending on where you mount it. Mounting can be done in the front trunk, under the tank, or in the engine compartment. It should have appropriate vibration isolation pad, stock or hardware store work well. Plan on spending about $150 - 200.

Misc: All that grade 8 hardware, clamps, fluids, sealants, wiring, and many trips to the hardware store or FLAPS will cost ~$300.

Plan a minimum of $4k for a very basic conversion if you do most or all of the work yourself. A full bolt together kit with crate engine with upgraded 901 ~$8k, and $15k-20k for a high hp built engine and stronger gearbox with associated upgrades. As with most cars, the sky is the limit.