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]

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.