The plan, such as it is.
... I want a nice old Benz, clean and tidy but not pristine, which will happily take me on a nice wine tour in France or a classic car rally. So reliable, brisk, comfortable and economical. Stance is about the only mod I can think of, but that can be left for a long way ahead.
For the reliable, brisk and economical bit, the 250 is OK - in original tune it produces 150 horses which in my experience is the right side of stately and the wrong side of brisk, so may need just a little pepping up. The results of switching my Citroen SM from D Jetronic to Megasquirt ECU etc have been revelatory - a really singing, flexible, much more economical (well over 60% better) and starts on button every time reliable car. I have no idea if the engine is generating more horses, but it wouldn't surprise me. The great thing about the switch is that no real engine work needs doing - just installing sensors and injectors. About the only thing that might need engine out is fitting a CPS - the SM had a drilled flywheel, but reading up, it might be possible to use the pulse from the electronic dizzy. More work required.
There is no doubt that the 250 coupe is a lovely , charming old car .
Despite what the figures in any books say , I'm sorry to say that I don't think that in the real world it will be all that economical .
I remember these cars from back in the day and , while the 250 is certainly a refined and pleasant cruiser , it isn't going to set the road on fire . A friend had one and I remember it being a thirsty beast , about on a par with my 280E which hovered at sub 20 mpg and you had to drive with a light foot to get into the low 20's .
My 220/8 was a bit better , returning mid to high 20's and , with gentle driving , could be coaxed into the low 30's .
Admittedly , my 220/8 and the 280E were both manual , so had the potential for better economy ( although my 280 with 5 speed close ratio box tended to be driven with 'enthusiasm' most of the time , so refuelling every 200 odd miles was the norm - thankfully petrol was cheap back then ) . My friend's automatic 250 saloon was probably at a disadvantage , economy wise , but I know he moaned a bit about its thirst . It was comparatively economical against another friend's W108 280SE which he reckoned got about 10-12 mpg in the real world ( mostly town driving ) though .
Perhaps your megasquirt conversion ( and maybe look at fitting a 123 electronic distributor ) will make a difference . LPG conversion may be worth looking at too ? That is , if you are thinking of doing high mileage in it - otherwise you have to weigh up the conversion cost against fuel savings ; if only doing 5000 miles pa , perhaps cheaper to just put up with poorer fuel economy .
Otherwise , you could always speak to the nice Mr Rhind about a diesel conversion - while the saloons came as Diesels the coupes never did , but not to say it couldn't be done .
Certainly , back when they were current , these were very pleasant and reliable cars to drive around in - I put close to a quarter of a million miles on my 280E with only two mishaps : once the gear lever came out in my hand going across a roundabout , leaving me with no gears until I was able to reinsert it ; the other time was failure of the electronic ignition module on the nearside inner wing . Not counting consumables like brakes , clutches , exhausts , tyres etc .
