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Discussion Starter #1
Hi, new member here :)

My friend has a 280SL that has some bad engine problems and has been quoted something silly to have it all put correct.
I happen to have a good complete 350 V8 engine, gearbox etc.. and he's asked me if I think it would be possible to be able to 'drop' it into his car without too much hassle?

Are the mountings etc.. the same? I know a lot of other parts will also need to be swapped over (suspension ...)

Thanks!
 

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68 250S, 91 300se, 98 SL500, 450SEL 6.9, 14 CLS550 Past MB's; 300SD, 300E, 300TE, 190E, ML420
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Just sell me the car.

I am just now completely rebuilding a 250S engine which is different but comparable, parts and outside labor will be @$4K. A cheby engine will drop value of car to 0.
A 280SL I believe is a euro car and the 280 engine is a desirable engine, both making a swap silly.
 

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1983 380 SL
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I would either fix the existing 280 or swap it out with a good replacement 280. The 280 is a very desirable and reliable engine. Just ask Nobby.
 

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Discussion Starter #4
I forgot to mention that I'm from the UK, so the 280 engine is more common here.

He's been quoted something like £5k for a rebuild of his 280, hence why he's thinking the cheaper option would be to buy my 350 engine and hope it drops in (with other work needed too).

Whether the engine mounts are the same?
 

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Outstanding Contributor
450slc5.0cab 280sl5sp 280se4.5 500seAMG +250seStkW108 350sl4spdX3 500secEuro
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Do you have the transmission for the 350? What model car did it come from? A 107 and the oil pan will fit. A 108 and the oil pm might fit. A w116, no go.

What fuel system is the 280sl?
What fuel system is the 350 engine?

The car the 350 came from will be the biggest factor IMO.

A m110 trans will not bolt to a 3.5.

The rear end for the 280sl is probably 3.69 or 3.58, and the rear end for a 350sl is usually a 3.46. If you leave that little 6-cylinder diff in there, the diff will probably be fine, and it will scoot off the line quickly. Fortunately the 3.5 revs about as high as the 2.8, but you I’ll find yourself with unnecessarily high revs on the highway. And, a v8 diff is what a v8 should get, not the smaller 6-cyl diff.


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1983 380 SL
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Your original post stipulated "without too much hassle". I cannot imagine a 350 (I assume Mercedes engine) replacing a 280 would go off without too much hassle". There are just too many things to consider. Just swapping one engine with an identical engine is a hassle and everything already fits and lines up (maybe). Tell your friend to get a few more estimates. £5k rebuild does sound high.
 

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It Is What It Is, Dude
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.



The 107 engine cradle is configured for a front oil sump location. SBC package is rear oil sump design. Moving the SBC rearward means cutting the bulkhead and tunnel areas. There are front sump kits for SBC but I think the oil pump bump out could still be a problem.


Not hardly 'hassle free' by any stretch.
 

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'72 450SL, 107.044-12-000422
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Maybe I missed it.

Swap with a “V8 from a 350sl” or with a “350CI V8 (GM/Chevy)”?


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450slc5.0cab 280sl5sp 280se4.5 500seAMG +250seStkW108 350sl4spdX3 500secEuro
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1989 560 Sel
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That specific car? Or just the same kind of motor?


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Motor, I had one for 10 years and if your 280sl is is the model I 'm thinking of it should be a drop in replacement. The 350sl/4 speed is a rare car, but I am not sure how rare the drive train was.
 

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450slc5.0cab 280sl5sp 280se4.5 500seAMG +250seStkW108 350sl4spdX3 500secEuro
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Motor, I had one for 10 years and if your 280sl is is the model I 'm thinking of it should be a drop in replacement. The 350sl/4 speed is a rare car, but I am not sure how rare the drive train was.


The subframe the motor bolts to is identical on basically all 107’s (and w114 and w115), but the 560sl came from the factory with an updated version that is less likely to break the control arm bolt tabs.

If your 3.5 is from a 107 (3.5 wasn’t offered in w114/115), then the motor mount arms will be perfect.

You might just need to get common 4.5 v8 parts. I’m not sure if the 3.5 has a lot of 3.5 specific external parts.


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'72 450SL, 107.044-12-000422
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Chevy "350" no, this "350" yes..



Mercedes-Benz 350SL is a European-spec example badged as a 450SL but powered by a 3.5L M116 V8 paired with a 4-speed manual transmission.



https://bringatrailer.com/listing/1980-mercedes-benz-450sl-11/


I get it. I have a NA 350sl with a M117.

Still not clear whether the OP is thinking of swapping out for a Mercedes V8 or a GM V8.

I think two very different prospects, both in terms of effort and resale value.


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First thought is that you are getting into a can of worms.
I have seen customers try and do similar projects and once they get into it, they are completely overwhelmed and wish they never started in the first place because there is ALWAYS something else that needs to be changed.
There will be more to this than you can imagine
Below is just a few reasons to stay with the 280

Rear end is different ratio, 280 rear will make the v-8 rev higher, poor fuel economy
Radiator will need to be upgraded to handle v-8, this will more than likely be a custom made radiator $$$
Oil pan will have to be changed for cross member
Motor mounts are different, possible custom fabrication to make things fit
Front springs have a different weight rating
Transmission may or may not line up based on motor mount alignment
Transmission and/or fuel linkage will have to be fabricated
May have different fuel systems
Resale will be nil

Need to get a few more estimates, 5K sounds high
Recommend that he keep the 280, historically a more reliable motor, less hassle all around, as I mentioned earlier, A CAN OF WORMS !
 

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450slc5.0cab 280sl5sp 280se4.5 500seAMG +250seStkW108 350sl4spdX3 500secEuro
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First thought is that you are getting into a can of worms.
I have seen customers try and do similar projects and once they get into it, they are completely overwhelmed and wish they never started in the first place because there is ALWAYS something else that needs to be changed.
There will be more to this than you can imagine
Below is just a few reasons to stay with the 280

Rear end is different ratio, 280 rear will make the v-8 rev higher, poor fuel economy
Radiator will need to be upgraded to handle v-8, this will more than likely be a custom made radiator $$$
Oil pan will have to be changed for cross member
Motor mounts are different, possible custom fabrication to make things fit
Front springs have a different weight rating
Transmission may or may not line up based on motor mount alignment
Transmission and/or fuel linkage will have to be fabricated
May have different fuel systems
Resale will be nil

Need to get a few more estimates, 5K sounds high
Recommend that he keep the 280, historically a more reliable motor, less hassle all around, as I mentioned earlier, A CAN OF WORMS !


Some good points here, but:
- m110 transmission will not work with v8
- if the 3.5 is from a 107, no cradle, motor mount arms, or oil pan mods will be required.

V8 to v8 swaps are more straight forward. I think having a 450sl parts car (same year as the motor for matching fuel systems and hoses etc, make sure it’s not k-jet vs d-jet, etc) would be good to have before embarking on the swap. Otherwise, getting nickeled and dimes to death with all the parts that will be needed to make it work.


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He mentioned that he had the V-8 motor with transmission,
did not mention which series motor he has or anything about fuel system on V-8

Nickeled and dimed is another good way to put it.
 
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