Engine swap for a 108/109 chassis - Mercedes-Benz Forum

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post #1 of 6 (permalink) Old 10-30-2006, 06:12 AM Thread Starter
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Engine swap for a 108/109 chassis

Has anyone here given thought to dropping the 5.6L from a 560SEC/SEL into the 108/109 chassis? If so, what problems did you find? It seems that replacing the old 4.5L with an alloy block 5.6 (~200lb. less weight) would make sense from a performance standpoint (obviously none of this is for economic reasons!) I was considering it for my '72 280SEL 4.5.

My thoughts were to add a more modern fuel injection control system such as those from FAST. (This is the one that Karl Middelhauve uses for his M-100 conversions).

Anyone have any thoughts???


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post #2 of 6 (permalink) Old 11-01-2006, 01:46 AM
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Should fit but the transmission will be needed as well. Also the front may ride high with the - 200lbs but easily solved.Speedo is electrical on the W126 versus mechanical on the W108 so you'll need that too.That's all that comes to mind at this moment.

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post #3 of 6 (permalink) Old 11-08-2006, 04:27 AM
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Great idea!

Is it going to fit? The 126 engine looks a tad bit bigger than the 108's engine bay, but unless you slap the thing in there you wouldn't really know. The engine mount would probably have to be relocated. I don't know if this has been done before (126 engine into 108). Then there is the matter of making the original gauges compatible with the later electronic circuitry. Transplant the whole 126 engine and tranny into the 108, balance the prop shaft, adapt it to the 108 differential, hook up the wiring and all the electrical connections. How about the brakes? Would the old brake boosters work with the new engine? If anyone is brave enough to try this, please document all the work you do, because I'd like to be next!

'68 280SE (w108)
'72 280SE (w108) 3.5
'88 560SEL(w126)
'97 E50 (W210)
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post #4 of 6 (permalink) Old 12-29-2006, 04:21 PM
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You can also transplant a Ford 289 engine (Mustang V-8) into these suckers (Benz-philes are probably frothing at the mouth right now). My dad did the conversion years ago, with interesting results. I have tried over and again to get the car into my loving embrace, but Dad refuses to sell it...
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post #5 of 6 (permalink) Old 12-29-2006, 05:51 PM
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There's a fellow on mercdesshop.com in the process of adapting a 560 (or was it a 500) to his 111 coupe. The task is similar, but yours would be simpler because the car was already adapted to the larger 4.5 v8. You shouldn't have a problem, presuming you know how to transplant all the electronics for the engine and transmission. A 500 is a simpler motor to work with computer-wise. -cth
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post #6 of 6 (permalink) Old 12-30-2006, 01:56 PM
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I have a constant challenge

I have a constant challenge with trying to get my 4.5 to get up and go. I have had it tuned by the pro's and they say they just can not figure it out. I have to pump the gas pedal to get fuel to the engine.

I have been thinking about changing the engine out because I love the car but I also love that it is ALL original. I would like to know how it turns out for you if you do change the engine out.
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