Need some input on diesel conversion of Mercedes

[gn3dr]

Hi
I am thinking about converting a '73 Merc 280 auto to Diesel. I'm really not a diesel fan but am coming around to doing this for economy reasons and also just to try it out.

What engines would you guys recommend? I guess it would be easiest if the engine was a Merc engine - but I know nothing about them and internet searches are just giving me information overload. It needs to be a turbo diesel for a bit of poke and I'd like decent power with good economy. The more modern the engine the better up to the point of not needing to re-code ECU's etc.
What kind of mpg do 300D turbos return?


Failing that my other though it a 525tds in and E28 or and E24. Thoughts? - or would the 3.0 BMW turbo diesel from a 530D be an easy transplant?

[gn3dr]

Oh have a mad diesel W123 burnout in exchange for your advice

[popuptoaster]

is yours an Efi 280? if it is i'd be more inclined to LPG it if it was mine seems a shame to chuck out the 180bhp 6 pot, if its shagged however i'd be looking at the lump from a merc sprinter van, it'll be in keeping with the car and get it shifting along ok, with a proper diesel noise.

[BenzBoy]

If you really want to go the diesel route I reckon a 3.0 5-cyl doesel from a W123 would be ideal, although they are sought after engines. I'm assuming yours is a W114?

The BMW M51 diesel is a nice engine although it won't be much better on juice than your petrol, and the transplant would be fairly complicated seeing as there are lots of electronics involved. I wouldn't bother with the earlier BM diesels really as the amount of work involved to get them fitted compared to the lack of power wouldn't be a good trade-off in my opinion - I'd sooner stick in a Merc 2.2 diesel as at least the parts just swap right in, ven though performance is sloth-like! ;D

I'd consider what popup said about LPG though - it'd be a shame to lose that smooth 6-pot engine!

[Oldbus]

If yours was built after 08.1973 then it should have Injection instead of carbs.

A lot of people converted the Stacklight to Diesel back in the seventies and eighties as the 280´s were always keen on plenty of oil and petrol.

The original 300D engines that came in the stacklight only had 80bhp and are not very good mpg wise.

The later W123/4 engines are better, have a bit more power but you´ll miss your 6 cylinder. The LPG route is definetely worth thinking about.

I´d get a 250D out of a W124 if it was mine - it´s bombproof, cheap to run and you can pick them up quite cheaply too.

You´ll need the gearbox out of the donor car, together with glow relay & electrics, propshaft, radiator. As yours is an automatic make sure the donor car is too

[gn3dr]

Thanks for the replies folks. Yes it's a W114 (or 115? I'm not sure). It's my brother's car and he hasn't been able to sell it so I just might take it off his hands for cheap ;D

It's a 280E - so I think it is injected. (I haven't even looked under the bonnet!). The engine is fine - the auto gearbox has a slight rattle in it when idling but it drives fine.

Unfortuntely LPG isn't really an option for me over here in Ireland as I believe there are only a handfull of stations in the whole country - and I think the nearest one to me is 60 miles away!

Is the 250D W124 a turbo engine? Must do a bit of googling. Looking at the market here I could pick up a 1995 300D for less than €500

I hear what you are saying about ditching a nice 6 cylinder but I've enought petrol guzzling yokes - so need something with some hint of economy about it! Any idea of mpg figures I could expect with a 250D or 300D?

[Deleted]

This is something I looked at recently too.

I've got a 114/115 220d which needed a new lump.

As has already been pointed out, the period diesel engines for these stacklights (in both four and five cylinder forms) had both the weight and performance characteristics of an anchor.

The 6 potter that came in the 123s and 124s is a good lump, but it it is really just too big to shoehorn into the space you have available.

There was an early TD 2.5 available - these tend to pop up now and then in 123 estates more commonly, but the cars have a following and seem to command too high a price to justify breaking one for its engine.

My advice would be (and its what I'm doing at the moment, after temporarily converting mine to petrol to keep me on the road - cheers Dean) to get hold of a 2.5 lump from a 190, or the like. They aren't going to net you any speeding tickets in a hurry, but they plod along well enough not to be a pain. They also go in easily - the sump is in the right place, they can squeeze between the bulkhead brace, no complicated wiring to get round, etc, etc.
These five cylinders don't sound too bad either!

Oh, nearly forgot - there is also a 2.2 four pot in the 124 too, not as common and only in the later models (possibly early 90's). Maybe worth a look, as they are more compact, lighter (obviously) and a bit more frugal.

Joe