Swap Info

Here's some helpful information for LS swapping your Boxster or Cayman

ECU and Gauges

I use a GM E38 ECU for the engine and I keep the porsche computer for the dash. Put a 986/996 porsche temperature sensor on the right side head and keep the Porsche engine compartment temp sensor, it needs these for AC and engine compartment fan. I use the Porsche computer to control the starter, fuel pump, and AC. Hook the Porche crank sensor wire to the GM crank sensor wire and the tach will work. Keep the harness off your original engine and strip put everything you don't need. I put a Porsche oil pressure switch on my engine and Porsche oil level and temp sensor in my dry sump tank. You will have check engine light with this method unless you also use an Arduino to filter the can bus messages. The other things that happened to me without the can bus filtering is the temperature gauge would go dead after about 30 minutes every time I started it, and the PSM did not work. To monitor the engine temperature I use the Torque App running on an android head unit because the porsche temp gauge lies to you anyway, it sits at 175 when the engine is from about 160 to 220.  I did this arduino filtering but the computer I used is not currently available. CPE may eventually offer a box to replace the Porsche ECU that handles all this. You can also use an aftermarket ECU for the engine and gauges like an AEM 30-7109. LinkECU now offers an ECU with Porsche integration.

Pedal

I wire the Porsche pedal to the GM E38. I recommend this for ergonomics rather than trying to mount a GM pedal. 

Dry Sump

Alot of guys that do track stuff want to do a dry sump but hard to fit an external oil pump and still keep AC. One option that works for this is to use the GM factory dry sump system that comes in corvette Z06 with LS7 and Grandsport with LS3 and use my accessory kit for alternator and compressor mounting. Some people say an external oil pump type system works better but I'm sure any dry sump system is better than no dry sump system. Any LS can be converted to GM dry sump but requires the right crankshaft, oil pan, oil pump, etc. I used a Peterson tank.

Engine Isolators

I tried the stock corvette mounts but they are too soft resulting in alot of engine movement and clutch chatter. Hinson are also too soft. 

I recommend these https://www.prothanesuspensionparts.com/7525 

Water Pumps

I use two Davies Craig EWP150s because they're inexpensive and power efficient. In these cars the water has alot farther to go to the radiators and back than in a front engine car, so there is more flow resistance. If you implement a PWM control for the water pump(s) be sure to check for voltage spikes with an oscilloscope. I had voltage spikes north of 24 volts that killed an ECU. These can be controlled with a TVS diode and capacitors. 

Power Steering

Since there's no room in the engine compartment for a power steering pump you'll want to install an electric one up front. It seems most electric power steering pumps will work. I use a Toyota MR2 pump. Porsche cup cars use a TRW pump. Others have used Volvo or Mazda with success.

Firewall and hand brake

You'll need to modify the firewall. This is where some people get squeamish but it really doesn't need to be a barrier. You can cut clearances and take the car to a body shop to have the new metal put in, or do what I did and learn to weld. TIG welders are fairly cheap now and being able to weld will open up a ton of doors with respect to the things you can build. It's a great excuse to gain a new skill. To keep the hand brake the hand brake mount needs to be pushed into the tunnel, when you do this the cables will be too long. To fix that some use a spacer on the cables at the wheels but I made a different mount for where they attach to the brake handle. I looked at using an electric actuator but didn't fine a way to do it I liked.

Transmission and Axles

The 986s and 987s 6 speed transmissions can both hold 500ft lbs torque. The gearing is nearly the same except for 5th and 6th where the 986s has taller gears that are a little better for a v8 in highway application. With the 986s you'll be at 3000 rpm at 80mph in 6th gear.  You will need the cables that match the transmission. I hear that 987 cables are a little short but for me 986s cables work fine with a 986s transmission.

You need to keep the engine as far forward as possible to help minimize axle angle. If you use a 986s transmission in a 987 car you need to use two of the right side 987 axles. You can't use a 986 axle in a 987 because the wheel hub end of the axles are different between 986 and 987.

Engine adapter, clutch, and flywheel

Engine adapter comes from CPE. Clutch and flywheel from Spec but can be purchased through CPE. A Stage 2 Spec clutch is good for 600ft lbs and has less pedal effort than the stock clutch.

Fuel System

The Porsche fuel pressure regulator is 55psi and this turns out to be close enough to the 58psi that GM specifies. The stock Porsche fuel system supports 500hp after an upgraded fuel line from the tank. The factory fuel line is a little small and before the line upgrade I saw about 10 psi drop in fuel pressure at full throttle and 7000 rpm. After the line upgrade that came down to 5psi. 

Flip the intake

On the LS you'll want to flip the intake around backwards. When you do that you'll find the oil pressure sensor is in the way. For a LS7 my solution to that was to machine the boss off the valley cover and buy the Katech adapter https://katechengines.com/i-30497941-kat-a4784-oil-pressure-sensor-adapter-gen-4-reverse-intake.html and here is the one for LS3 https://katechengines.com/i-30497942-kat-a6678-oil-pressure-sensor-adapter-gen-4-reverse-intake.html

Steam Ports

Your engine will end up with the front slightly lower than the back, so plug the front steam ports and use the rears. 

Oil pan

The oil pans that are confirmed to work with my subframe and won't hang too far out the bottom are C6 LS3 for wet sump and LS7 for dry sump

https://www.improvedracing.com/c6-corvette-ls2-ls3-wet-sump-oil-pan-dimensions

https://www.improvedracing.com/c6-corvette-ls7-dry-sump-oil-pan-dimensions