What are the engine swap options for the R107 Mercedes Benz SL?

This blog will answer the following question: What are the engine swap options for the R107 Mercedes Benz SL? Should you do an engine swap or rebuild the engine?

What are the engine swap options for the R107 Mercedes Benz SL?

The engine swap options for the Mercedes Benz Sl R107 are listed below. 

  • M117
  • Chevy V 8 small block
  • M113
  • OM 617

Let’s take a look closer look at each of the engine options:

M117 engine 

It is a 5.5 litre V 8 engine and Mercedes Benz also used it in SL560. The M117 is a very good choice for engine swap in R107, very minor changes are required in the chassis. The M117 can fit in the engine compartment without any modification to the bonnet.

It can be used in the old SL models like SL 280,300 and 380. The lower section of the oil pan must be replaced so that the underbody shield can fit properly and no modifications to the subframe or drink axle carrier are required. 

The M117 had only 2 valves per cylinder and a single overhead camshaft with a double timing chain. It is a reliable engine with a bosch Jetronic fuel injection system, the power output is around 300 horsepower and 450 Nm of torque.

The advantage of swapping the old engine in the R 107 with the M117 is that it can be used with the 4-speed automatic or 5-speed manual transmission that is already available in the SL. No further modifications are required for the rear axle or the final drive of the car.

The cost of the engine swap with M117 is very less as there are plenty of W107 or R 107 available in the used car market. The registration of the vehicle can be easy in this case as only minor changes are needed for the engine swap.

Chevy V8 small block

It is a V8 engine manufactured by the Chevrolet division of general motors. The small block LT first and second-generation engines came in 4.3 to 6.6-litre displacement. If you want a more modern engine in the SL then the LS third and fourth-generation engines feature fuel injection and double overhead camshafts.

LS engines can also run on the E 85 fuel with some modifications to the fuel pumps located in the fuel tank. The biggest challenge to using this engine in the R 107 is the engine mounts. Old engine mounts cannot be used on the chevy small block engine.

New engine mounts must be fabricated from scratch and based on the R107 models, certain modifications are required for the radiator fan, and AC compressor. It is not a complicated job but it is time-consuming.

The power output of the chevy small block is good, generation 1 and 2 engines can easily produce over 300 horsepower. The standard gearbox in the SL is not compatible with the chevy small block, it will need modifications to the driveshaft if the transmission of a general motor is not available.

M113 engine 

It is a V8 engine based on the M112, Mercedes Benz also used it in a few AMG models. The M113 engine is lighter, engine blocks are made from aluminium and silicon alloy. The cylinder heads are also made using the same material.

There is a single overhead camshaft and 3 valves per cylinder. Some of the other features include a sequential fuel injection system, iron coating on the piston skirts, and fracture-split forged steel connecting rods.

It is a great engine swap option as it adds a modern system to the classic car body. One of the biggest challenges is to get the engine control unit and the transmission control unit to communicate with each other.

Mercedes Benz changed the drive authorization system in the 1990s so along with the engine a working electronic ignition lock is also required. M113 with a 722.6 transmission will require fewer modifications as the standard transmission will not be able to handle the increased engine output.

Some after-market control systems are available that will give full control over the engine and transmission system. Otherwise, an authorised Mercedes Benz diagnosis tool will be needed to diagnose any faults in the system.

The front subframe will need a few modifications for the engine mounts but it is not as complex as fitting a chevy small block. There is also plenty of clearance for the engine hood to close completely.

OM 617

It is also one of the popular choices for an engine swap, the OM 617 is a very reliable 5-cylinder diesel engine. Mercedes Benz used it in passenger as well as commercial vans from 1970 to 1980. Therefore, finding a used or donor engine for a swap is not difficult.

The engine is even capable of running on alternative fuels like biodiesel or vegetable oil. The displacement of the OM617 is 3.0 litres and it is a heavy engine. The crankcase and cylinder head are made completely from cast iron.

The fuel system is mechanical with an indirect injection so it does not need any electronic control unit. The power output of the engine is 227 horsepower and 250 Nm of torque. It is not powerful compared to some of the petrol engine options but due to the reliability and the overall price of the project, it is a sensible choice.

The OM617 will fit in the engine bay of the R107, adding a hood scoop or a vent is recommended as the diesel engine tends to get hot. Modifications to the steering gearbox and the engine oil filter body are necessary to properly install the engine mounts. 

Should you do an engine swap or rebuild the engine of the Mercedes SL R107?

Mercedes Benz sold more than 200,000 units of SL (R107) in the USA, so there are plenty of cars available in the used car or scrap market. It is easy to find a donor car or engine and transmission assembly.

Rebuilding the engine or transmission from an authorised dealership can cost 5000-15000 USA, therefore it is worth doing an engine swap. While doing an engine swap, ensure that the subframe requires minimum modifications otherwise the fabrication work can be very expensive.

Conclusion

This blog explained some of the engines that can be swapped in an old R107 chassis. Doing an engine swap can be cheaper compared to an engine rebuild but it also devalues the car. Also In some countries, the vehicle may need new registration and roadworthiness certificates. So all factors must be considered before making the decision to swap the engine.

What was missing from this post which could have made it better?

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