I've read the few threads on this forum about engine swap options for R107 SLs, and I know there are those out there who cry heresy when people bring up the topic of engine swaps in a classic car.

I've seen online that people have put in LS1s, M-B V12s, and M-B I6 diesels, in addition to the more common 560 or Euro 500 swaps which are much easier as those engines were available in the R107 chassis from factory.

While I don't technically have the car yet, I've arranged to acquire a 1981 380SL west coast car in the spring, once the mountain roads have been cleared, and I can feel comfortable driving it across the Rockies. I know the current owner very well, and the car has been well cared for since he bought it in ~96/97.

I appreciate that the car is a GT cruiser, not a sports car, but 155hp when new in a 4000+lb car seems a little too relaxed. My 2700 lb hatchback has almost that much power, and isn't exactly a screaming machine.

While the current SL 550 works out to be about 8.8lb/hp, I don't think having substantially more power in an old 380 would create the image of trying to turn it into a sports car, but rather a more powerful GT car.

From what I've read, I understand that the engine bay is quite narrow for a DOHC V8 or V6 from more modern Benzes, but with M-B moving towards inline 6s again, I was wondering what more informed people thought about putting a new M256 in an old R107. If the narrowness of the inline 6 would create an opportunity to significantly upgrade the power without significantly modifying the engine bay. ~408hp (10.5/lb) with modern efficiencies and engine management is very appealing to me.

Apart from sourcing an engine that hasn't made it to north america yet, I expect sorting out a transmission to match the engine and fit in the tunnel would be the most challenging issue. Subframe modification would undoubtedly be required, but considering the challenge of the rest of the swap, it wouldn't be insurmountable.

What are your thoughts?

 

I'm doing a similar build and am very green to all this myself. From initial research, the folks who have done something similar were a company called Mechatronik, who's M coupe's feature updated a W113 engine from the W220 S55 AMG. That's what I'm shooting for my build.

I wish you well and tell me what you find.