I've looked on here and I cannot find anything about this swap specifically.

It seems to me that if I were longing for the power of a 6.3 in my 108 the easiest thing to do would be to replace my 4.5 with the big engine (and tranny I assume). This would alleviate the worry of the airbag suspension and other various 300 SEL peoblems. The cars with bad whatevers seem to go for peanuts.

Has anyone done something similar? Are there suspension concerns? How about rear end swap/stock?

I am not saying that this is what I want to do....Just thinking that if I want to build a real sleeper, this would be the way to start.

Paul X.

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Pxland

2001 Honda Accord

1995 Jeep Cherokee

1973 MB 280SEL 4.5

You'd definetly need to do the rearend too. Geared differently, plus the 6.3 might tear the 4.5's apart. But you will want the limited-slip of the 6.3.

The issue is that the 6.3 is a lot heavier than the 4.5. You'd need to reinforce the springs up front somehow or deal with sagging.

You'd need the engine, tranny, rearend, and exhaust system from a 6.3, as well as the injection pump, and radiator. If you have a complete 6.3, you can do it easily enough I would imagine. I have no idea how much heavier the 6.3 is than the 4.5, but I would think it's enough to cause some serious sagging. I'd personally stick a 5.6 in with its matching tranny before a 6.3. Better milage, no spring changes needed (hell, the 5.6 is lighter than the 4.5, being an aluminum block).

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Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k

I don't know of any 300SEL problems. The airbag suspension when properly serviced is a very smooth ride near as nice as my sons S500 just a little softer, as a mater of fact I prefer it to my girlfriends 560SLC or my sons S500. The 300SEL is a superior car for that very reason. Why not just find one with a 6.3 from the get go. Now if you want to improve the 300SEL 4.5, or the 108 consider a 560 engine a far superior EFI system and really good power.

ive had 2 big suprises with the steering wheel turned on my 300sel 3.5.

1. the rear end breaks loose first! i expected the thing to go straight, but the rear end came around, very slowly and predictably too

2. the other day i found myself behind a new s4 going into a 180degree on ramp to the freeway. traffic cleared in front of us and we both got on it. i actually was catching him until it straightened up and his power advantage took over.

these things handle better than they should!

mike

The hassles of adapting a 6.3 engine into a standard 108 are legion. It will entail widening the transmission tunnel, changing around the power steering box, frame, firewall, and other changes. Also, as was mentioned, the 6.3 engine is a HUGE heavy lump and too heavy for the spring front suspension.

If you have ever looked closely at a 6.3, the front axle is moved slightly forward, perhaps an inch or two, in the front wheel well. Again this is an "on the fly" adaptation that was made to accommodate the engine in a car that otherwise wasn't designed for it.

Your best bet is just to go and purchase a 6.3. Beware, and know what you are getting into, though. If you are interested, you can see the presentation on the topic that I recently created:

http://homepage.mac.com/gerryvz/M-100_0.9.pdf

Cheers,
Gerry

You could just get the 6.3 in the 109 and convert it to spring suspension if the air suspension fails. I would think that that would be your best way to go both in ease and financially. I've heard of others doing it so I'm sure there are kits available or one could be made up.

Thanks
David

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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Just in case this was missed, the biggest and most difficult swap is the wiring harness. All the items Gerry mention are daunting as well an easy to botch. The weght difference between the 6.3's M100 and a 3.5 (I don't know what a 4.5 weighs, thus the 3.5 difference), is exactly 255 pounds. As Gerry said so well, buy a good 6.3. As the last advice stated, if you are afraid of the great air system, replace that system with coils.
I minor suggestion. But any Benz with a 3.5. That 255 pounds needs 25 horse to carry that weight. The 3.5 can be altered to a point that it can challendge a good 6.3. Does a coil Benz weigh less than an air system Benz? I think so. My choice would be a 111 Coupe with a 3.5, in this example only. I'd prefer a 112 Coupe with a 3.5, myself. Then given the choie, an altered 112 Coupe with a 6.3.

My Mechanic suggested this to me when I had all the problems with te 4.5 engine and injection. You can buy a 5.6 engine fairly cheaply and its more similar to the 4.5 thats in there (which is also an m117). He also said that the K-Jetronic mechanical injection is simpler and easier to adapt and the 4 speed auto can also be adapted.

The Euro spec 560SEL's had 300 horsepower which should be plenty of power .....

I thought about it

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With best regards

Al