Hello forumites.
I've just aquired a 111 250se convertible in need of a little TLC.
It's a driver but I've got to do some chassis work for MOT.
I have in my yard a rotten 108 280SE 3.5 and am contemplating swapping the drivetrain, just for the hell of it really, and was wondering if anyone can point me in the direction of a description of the conversion in order that I can decide what to do.
The donor 108 is absolutely rotten, so no panels are re-useable and also the ECU is missing.
I'm considering installing a modern programmable ECU and perhaps replacing the distributor with one without the trigger points.
I've been turning spanners on Mercs for 30 years so am really looking for someone who has done this before just so I can minimise the conversion and learning time.
A real bastard option would be to install a 560 117 engine!
Any pointers appreciated.
Colin

My car is a '62 W111 and the previous owner swapped all the running gear out of a 3.5 Coupe. It's mostly a bolt on. You will have to relocate the brake booster a bit outwards, unless it clears on rhds. The wiring will also need some tweaking to integrate the Djet system. You will also have to modify the top of the trans tunnel to adapt the 3.5 shift lever. Finally the 3.5 radiator will require some adaptation, but it's doable. The rest is a direct bolt on.

I have put a 5.6 in a W111 Coupe some time ago and am currently planning to fit a euro 5.0 in my 62 Coupe. It would not be much more work than the 3.5, especially if you want to megasquirt it, as you may be able to reuse a lot of the Djet system (injectors, fuel rails and pump etc. You may then consider using a 4.5 Djet intake manifold out ofa early W116 450). In addition to the above you will have to work out some enxhaust manifolds. Some out of a rhd r107 500 or 560 SL are your best bet. For the speedo you may also have to get a system that translates electric signal into a turning cable. There's a firm in the US that does that. If you go with a 5.6 you ma consider change the rear end with 6.3 crown&pinion and homokinetik joint. Mercmad 6.3 has also performed such conversions on rhds in Australia and may in aqddition guide you for a W124 rear end swap if you want to go that way.

Good luck! Keep us posted!

Thanks for the quick reply.
I'm off on holiday on Monday so will have time to try and get my commercial head on instead of my petrol head!

Hi,GGR is right,your 250 is really just the same car as the 280SE . There is a slight difference in the tunnel. Just forward of the front seat box section on the floor. The tunnel is lower on the 220-250 cars. Remove the rear part of the tunnel so the flex disc clears the floor and make a box to fit over the top and to mount the shifter. I have also simply removed the tunnel from a 3.5 and used the trans mount section in a W111 to do the same job.
Install the front axle with it's bigger brakes and the diff to get four wheel discs if you haven't got them already.
I say this because we had W111 220SE cabriolets here and 3 x 300 cabs and and handful of 3.5's but no 250's so I've never seen under one.
I am not sure but's possible the 250 has the same steering geometry as a 220 and the steering idler and steering box box pitman arm are lower .When putting a V8 into a 220 the drag link rubs on the sump...so the later W108 pitman arm mount is utilised to lower the assembly for clearance. You have one on your donor..
Everything else is simple.
I had thought of the later W116,107,123 diff etc but having spoken with a friend in the last day or so i have decided the better option is in fact W124 and W201 diffs. They are a complete unit and very compact requiring little floor modification to install .
There is a guy in the UK who installed a W123 diff into his W111 coupe and found he had to have special springs made because both W111 and W123 springs were too soft and the leverage under aceleration caused the rear of the car to drop.

A while back I was reading "Mercedes Enthusiast" (U.K. publication that Barnes and Noble usually has a couple months late) and there was an article about a U.K. firm that takes the 3.5L V8 from 70-72 and converts it for use in a pagoda SL. Since your W111 is almost identical to a 280SE the firm I mentioned earlier probably has some really good pointers on such an engine swap. After all, if they can cram the 3.5L V8 into a Pagoda, they can probably help with your (much simpler) switch. I'll do some digging to see if I can find some contact info on them for you.

Edit: I demand pictures when you're done because the W111 is G.O.R.G.E.O.U.S. and with that little 3.5L under the hood, well, lets just say I'm drooling already.

A 3.5 in a pagoda is just 'scratching' the surface.

What engine is that?

http://www.youtube.com/watch?v=PMnHlrNLDqU

Looks like an AMG V8, shows up at approx 1:30 of the clip.

A 3.5 with its engine, tranny, axle and rear will bolt in. As GGR stated, some workarounds will need to be done. Used ECUs can be bought cheap enough in the US for 4.5's - I assume 3.5 ECUs are cheap enough in Europe on eBay or similar sites. You'll need the fuel pump, probably new fuel rails. The other thing is making a custom ECU harness or modifying one from either a 3.5 or 4.5. Your ECU probably wont be able to fit the same location it's in on a 108, although it may be ideal. Other than the drivetrain requiring perhaps brake booster repositioning, use the brakes off the donor car (vented front & rear discs, calipers, as well as the master cylinder and booster) for an easy brake upgrade!

__________________
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

M113 AMG 5.5 liter . A bit bigger and more powerful than the 4.8 in the car in the video.
I can buy one here for $15,000 from a ML55. NOT

Hum... When is it that they're going to put an M120 into something? Being a 60° engine and not much longer than an L6 it should fit. And from Roncallo's experience, it is not heavier than an iron block M117... A W111 Coupe or Cab would be a good candidate !

Brabus has been doing it for years,Putting V12's into W124's etc.
Heres something else again.
http://www.mercedespower.de/w123_alt-motor_ausbau.html

After spending some time relaxing on the beach I've come back with my business head on.
I'm going to stick with originality and save the V8 for another project, hopefully a pagoda 113!
If i was going to undertake this I would want to facelift it to a 108 front end which would start to get expensive.
Thanks for the useful info to all who offered it.