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Conversion kit for the OM603 diesel engine


In 2005 Gösta Lindgren from the company SMT in Gothenburg mentioned in some mails that he wanted to convert some C30x to diesel engines. He wanted to produce conversion kits out of the experience with this first conversions, to sell a set of nonstandard parts, which are neccessary for the engine swap.

In the end of 2006 he is a step further, the first conversion - with a Mercedes-Benz OM603 engine - is finished and some conversion kits are ready to be sold. Also the complete car is available as well as the old Volvo B30A engine.

Gösta did send me some pictures and documents, which I publish here, because I am happy about everything about the old Volvo, and I say thanks to everybody, who is adding somethning to the possibilities of the car. The first picture shows the parts, which are content of the kit.

content of the conversion kit

The documentation for the usage of the kit can be downloaded as PDF-file. In this file the more than 40 pictures are missing, but I inserted some on this page for example. Gösta is in the forum with the nickname SMT.

frontside of the OM603

Mercedes-Benz OM603

The used 6-cylinder straight diesel engine with 3 l volume is a classic stationary head without turbo hightech or lots of electronic. It is well known from the Mercedes W124 series or from the Mercedes 300 GD of 1990. It is a fine engine with relativly high rpms for a diesel, built for long range sedans and station wagons. Power, torque and rpms are quite near to the data from the Volvo-B30A, except of the engine swap all main parts form the transmission chain can be unchanged.

One of the changes made to the engine is the position of the alternator. This has to be changed from the right side of the B30A to the left side of the OM603 in driving direction. The neccessary parts therefore are included in the kit. The picture on the left shows the OM603 with changed alternator.

But the starter and glow elements are still for 12 Volt, that is a little flaw in the conversion concept. A third battery and a strong converting charging unit like for a campmobile would be a good supplement. As I found in the german Flyer of DMV the starter and the fuel stop valve is available for 24 Volts - and for sure the glowing system as well. Unfortunately the engine data in this flyer are only for the marine version of the turbo engine. (I copied the PDF to my server to avoid the traffic for DMV)

exhaust from aboveexhaust from below

mounting details

A little bit difficult is the adaption of the exhaust system. On the pictures you can see the nice welding work on the exhaust pipe.

With a flexible tube the connection to the original exhaust system. This stops the vibrations from the engine.

From the injection pump a fuel line leads back to the right side of the fuel tank as an overflow.

exhaust from behindDiesel overfolw

The complete fitted engine is a little bit bigger than the original one. The airbox needs more space, therefore the engine cover in the hold needs some changes. too.

The more simple constructed inlet for the diesel engine gives the opportunity to change the position of the airbox high under the roof. In that case the engine cover needs only a hole for the tube and can be left unchanged.

OM603 fitted into the Volvo C303


The best technical data for the engine of the series W124 I found on www.meinbenz.de, for more interest in data of Mercedes-Benz cars I can recommend this german site.

engine straight 6-cylinder. Diesel OM 603.912 
bore x stroke 87,0 / 84,0 mm
volume 2996 cm³
produktion  01/85 - 08/89  01/85 - 08/89 
PS (kW) at rpm  109(80) at 4600  113(83) at 4600 
torque DIN Nm at rpm  185 at 2800  191 at 2600-3050 
compression  22,0

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