lapki1021

Hi everyone,

Need some of your advise. My 1991 300SE is aging, and I really like it. I am thinking to do a complete engine and transmission job on the car. It has over 200k miles. My idea is swap engine and transmission from newer E320 or even E420 (1995 after). Please feel free to share some of your thought and idea.

Thanks!

Sam

C43AMG

Why the engine swap? Why not just drop a new stock motor and tranny in instead of creating a Frankenstein car.Never create more headaches than what you need.If you need more power go get a different car.

Hattaresguy

Hmm putting an M104 would be an interesting project.

I hate to be a wet blanket but can you do this yourself? If the answer is no then well forget about it unless you want to spend a fortune. Buy a newer car.

The trick would be carrying over all the needed electronics and make it work and look factory.

schwarzwagen

Sam,

the E320 M104 bolts right in and has been done before. the E420 M119 cannot be easily done because of the electronics, but a 1990-92 500SL M119 has been done. Either way, both are potentially viable options. Keep in mind, no one has been able to successfully transplant a later (post 1992 for the V8s and post 1996 for the I6) engine because of the sophisticated electronics package. In a nutshell.

Physically speaking the M104 inline 6 is a direct swap, the M119 requires you to relocate the secondary firewall more aft requiring relocation of the battery tray, washer fluid reservoir, and other components. It's a pretty time consuming process, however not impossible.

Since you have a 300SE, I believe the M104 I6 is you only real option because the early SL V8 uses a modified injection system similar to the 560 whereas the M104 uses a modified system based on what you have presently. It is not feasible to mix the two unless you get a donor 560 and pirate the ENTIRE electronics package as well as the injection system and start from there, removing your I6 system completely.

If you found a C36 M104 from '95 or '96, that would work too.

schwarzwagen

this is where i come down on this. i have done the research and toyed with the idea for years, but when you get right down to it, it's just cheaper to buy a whole other car. like a w124 400e/e420, for example, is only like $6k, less than the cost of the engine swap and is a good car with an m119 v8.

the only reason to do this would be if you really like wrenching and want something that no one else (or few ppl) has/have. there is no financial incentive, heck if you want more power, go get a nice 560SEL and put euro headers and exhaust on it, done!

w123_w126

Yes, but it’s not a 126. It may not be logical or feasible but if the thread author’s like me he loves and wants to keep the 126 body style.

I’d install the 104 as noted above. Or also as noted above drop in a rebuilt 103 and keep the 126.

Mean-Benz

restoring the origninal 3 liter I6 is the best idea imo. maybe you know a company which can do that for you, or do-it-yourself.