Porsche LS3 Wiring

Wiring the Porsche LS3, perhaps the most daunting of tasks was not to be taken lightly.

LS3 Wiring Harness

Wiring the engine with the GM performance universal wiring harness was very painless and simple, with each connector properly labeled.

However getting the GM electronics to talk to the Porsche electronics was a task in itself. To bring life to the factory Porsche LS3 gauges and other chassis powered units and devices, we had to strip down the factory Porsche engine harness and adapt the original sensors to the LS. This process ensured that vital information could be communicated to the car itself as well as the important task of starting the Porsche LS3 with the starter signal and alternator power. Although there are still warning messages as expected, we were able to get full function of the factory gauges, tachometer, water temp. and oil pressure.

Porsche LS3 Cooling System

There are many items to consider in a Porsche LS3 swap, and the next item to consider is the cooling system. With the fuel system sorted out utilizing a nice set of Holley fuel rails and custom lines, we could begin adapting the Porsche LS3 cooling system. Although the routing of the Porsche LS3 cooling system can seem a bit “complex” it is fairly simple and utilizes most of the stock hard pipes.

We opted for the Renegade Hybrids electric coolant pump and front adapter plate to optimize space constraints. The rear-most hard pipes were replaced with flexible hose supplied with the kit to adapt to the stock remaining Porsche system.


Porsche LS3 UnderbodyPorsche LS3 Water PumpPorsche LS3 CoolingPorsche LS3 Cooling System

Converting the Porsche LS3 Fuel System

The next thing to address is the Porsche LS3 fuel system. With the Porsche engine and the LS engine sharing the same style “returnless” fuel system, the setup should be fairly simple.

From the diagrams below you can see the differences between a conventional return-type system and a returnless system. The return type utilities a pressure regulator after the fuel rail and the returnless system uses a pressure regulator before the fuel rail.

Fuel system 1 fuel system 2

The LS engine does however operate at a different pressure and as result, demands more fuel. Because of this, we will need to run a different fuel pressure regulator and an upgraded fuel pump. The Porsche uses an integrated fuel pump and pressure regulator unit in-tank, this difference will result in some customization to get everything mated together.

Another issue we encountered, was that the clearance between the intake manifold and the top of the engine bay is extremely tight. To eliminate this, we will be looking into a Holley performance AN flanged fuel rail to eliminate the stock fuel rail crossover tube.

Porsche LS

Porsche LS3 Fuel Rail

Porsche LS3 Fuel System

Test fitting the LS in the Porsche

The time has come to test fit the engine and transmission in the Porsche chassis. We did the prep work on the engine, which included installing the clutch/flywheel and mating the LS3 engine to the Porsche transmission via an adapter plate. We then installed various components on the engine, such as the alternator and mount plates. The next step was figuring out how to test fit the compilation in the Porsche.

Since there was no way the engine was going to drop in from the top, we decided to put the engine/transmission on a steel work bench, and drop the chassis on to the engine.

porsche 2 porsche v8 1

After a few modifications, the engine fit pretty easily!

Porsche 3 Porsche 4 Porsche 5


Project Outcast Begins..

This project started because the owner of the 996 Porsche C4S came to us with a blown engine. It turned out that the cylinder walls were scratched badly, which caused knocking in the engine. The only way to get this car back on the road would be to rebuild the stock engine.The problem is that no one likes stock! Where others saw a problem, we saw an opportunity. We presented the options to the owner of a stock rebuild, or doing a complete LS engine swap. We had been in communication with a company in Las Vegas called Renegade Hybrids, who specializes in LS swap conversion kits for a variety of older generation Porsche vehicle. There are a few advantages of doing an LS engine swap vs. a rebuild.


  • more hp, more torque
  • similar costs
  • GM factory warranty for the engine
  • cheaper maintenance
  • retains stock transmission
  • increased reliability
  • its a no brainer!

So after various discussions with the owner, he decided to go ahead with this project. So we ordered a 485hp version of the 6.2L LS3 in crate engine form, and ordered the necessary conversion parts from Renegade Hybrids. After that, it was just a waiting game for the parts to arrive!


Porsche LS parts