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Am I in the minority here choosing an M50? (it appears 2:1 in favour of the M20 v M50). I often wonder why there appears to have been more builders choosing the M20 engine option?
Technical engine?
Technical kit?
Cost?
As a Cabrio builder I was always going to put a straight 6 BMW engine into a Ford donor based car, so my choice of donor BMW was possibly a little less restricted. I researched the BMW engines in some depth, and concluded the most modern and efficient up to date engine, without running into electronic problems, would be the M50 vanos.
here's what I think people have chosen (apologies for any inadvertant errors):
Sportsters - unless stated otherwise:
M20
Patrick
Peter
Goo
Robin
Simon - Cabrio
Alfie
Peter Morris - Cabrio (MOC Tech.Advisor)
Will
Mike C
Sorton
M50
Andy Dane
Chris Cunliffe - Cabrio
Rob Dorey
Jeremy -Belfast
Mike - Cabrio
M52
Jeremy Ward Z3M3?
Timbo
Mike C
Peter - 2nd engine!
Other /Unknown
Kieran 318i?
Stuart?
PJ - Cosworth 2.9?
Chris Cussen - Ford Pinto?
Would anyone else like to add/amend their names on the list and give us reasons for their choice of engine?
M20 due to cost of donor cars at the time and all parts coming from a single donor. I'd quite happily drop an M52B28 with the M50B25 inlet manifold and a remap into it though, it's cost / time thing and I've already invested a lot in the M20 having rebuilt it as an M20B28
I was very 'green' when I started out and I think an e36 didn't even cross my mind?
I think they must have been just too expensive at the time to even consider.
I bought the first donor car i went to look at and assumed the Marlin kit came with everything else I needed! Oh how niave!
Mine's a 2.0L 8V DOHC (I4) engine running on carbs. Chosen because I bought a Seirra as a run around while I fixed my Spartan Treka, and that's what it had in it.
Like many others I started with an E30 donor (which I had owned since 1990). At the time I ordered my kit the E36 was not mentioned so was not even considered.
Time has moved on (which is more than can be said for my build) and I am now in a quandry. My M20 engine has a known history (head gasket change due to head corrosion) and with 150k miles on the clock is not in its prime.
I had always intended to put the existing engine in then find a replacement M20 if it failed. However, M20's are now old, high mileage and becoming scarce so should I be looking for a good condition M50 for initial installation?
The next question is Vanos - 0, 1 or 2. I believe the M50 started without then went to single and finished up double. Does anyone know the change dates and where does a cat come into the equation?
[QUOTE=Sorton However, M20's are now old, high mileage and becoming scarce so should I be looking for a good condition M50 for initial installation?
The next question is Vanos - 0, 1 or 2. I believe the M50 started without then went to single and finished up double. Does anyone know the change dates and where does a cat come into the equation?
Finally, can my M20 gearbox be used with the M50?[/QUOTE]
Sorton
The M20 will be an easier build as you have a single donor, and the electrics are simpler. That said the M50 electrics are managable provided you buy the complete engine loom and ECU with the engine.The M50 would require its own gearbox. To install M20 and then change would mean a considerable amount of extra work. Choose one and stick with it.
The M50 was initially introduced without vanos, and was then single vanos was added: I believe double vanos only appeared on the M52 - this was the version that had nickasil bore wear p[roblems - so best keep clear of this, unless you can prove it had a replacement block. The m54 has double vanos, but comes with EWS the fiendishly difficult security interlock from engine loom to dash instruments and key fob - not sure anyone has cracked this yet.
I went for a low milage M50 (67,000) on the basis I would not touch it, but drop it straight in and hope to have 50,000 trouble free miles. I chose with vanos as it delivers smoother power lower down the rev range. But there are those who say this adds unreliability - time will tell.
CATs are not required on an engine of provable age until August 1995, so a late M50 out of a cabriolet or 5 series drops just right. BMW will provide a letter stating what year an engine was manufactured if you provide the engine serial number: this meets with the DVLA requirement to determine the CAT position.
Mike
Thanks for your thoughts. I agree that, in an ideal world, I should go for a low mileage M50 (with or without single vanos). However, I have the M20 in my garage and a check on the contents of my piggy bank tells me I should use the no cost option! I am also familiar with the M20.
Hopefully, there will be a few M20's around in years to come, but if all else fails I can always re-work the one I have.
I don't think VANOS is the big problem the interwebz seems to portray it as. I've got an M54B22 in my daily driver and that has just under 98k on it and I've not had an issues yet, other than an a broken oil sensor. It's been running on LPG for the last 20 odd k as well.
With regards to the M20 the bottom end will happily do over 200k without anything needing to be done. If you look at the pics of mine (about 115k) the bottom end looks like new. The head could do with some work at that mileage. I didn't bother with valve guides or new valves but that would assure another 100k miles. Everything else was fine, the valve seals were not perfect any more and needed quite a lot of grinding to get right. New gaskets all round (especially the valve stem oil seals) was also good for it. My oil pump was perfectly fine too, I did swap out the cam for a hairy one but the original showed very little wear. The inner valve springs had shrunk slightly but I replaced those with higher spec ones anyway.
I think if you have a M20 with around 100k on it then it should be fine for another 50 without much if anything needed to be done. After than the head would need a bit of attention.
