Is this an M30 or M90?

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dave9118
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Is this an M30 or M90?

Post by dave9118 »

Hi all,

Im looking at buying my next 635, and I've come across this one that is advertised as having an M90 engine. Problem is, it doesn't look like M90 pictures posted on google, but the inlet manifold does look like my M30.

Did they make the M90 with this inlet manifold?

This is a 1981 euro spec car.

Thanks...
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dave9118
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Re: Is this an M30 or M90?

Post by dave9118 »

Sorry, here's a pic :-)
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Re: Is this an M30 or M90?

Post by bpoliakoff »

Basically your picture is of no help. A picture of an intake manifold used on both M30 and M90 motors proves nothing It should be an M90 if original as all euro 635s through end of 81 model year were M90s, but other parts of the engine shown and barely able to be seen leave it questionable I have an 81 euro that is a May build and with better and more complete pictures can probably help you
Last edited by bpoliakoff on Sat Dec 22, 2018 8:37 pm, edited 1 time in total.
81 Euro 635 M90 with motronic. Currently under a complete nut and bolt restoration. Pictures at
flickr.com/photos/bertsphotos.
dave9118
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Re: Is this an M30 or M90?

Post by dave9118 »

Wow! Many thanks for such a comprehensive and informative answer, I feel a bit better about it now. I haven't viewed the car yet, but at least now I'll know what to look for!

Thanks again, and merry Xmas :D
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Brucey
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Re: Is this an M30 or M90?

Post by Brucey »

that car is a 'series 1' car and (like all built before 5/82) is a somewhat different animal to those built after that date. It should have a 3.5 litre engine with a wide bore and a short stroke configuration which is often called an M90 (although in fact it is a type of M30). At that build date with that manifold on it ought to have Motronic engine management with a -002 ECU.

These series 1 cars have very few parts in common with the later ones; the chassis underpinnings went from being based on the E12 five series to the E28 five series after 5/82 and hardly anything (the glass, the seats, the body shape being exceptions) was retained.

cheers
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dave9118
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Re: Is this an M30 or M90?

Post by dave9118 »

Brucey wrote: Sun Dec 23, 2018 1:58 am that car is a 'series 1' car and (like all built before 5/82) is a somewhat different animal to those built after that date. It should have a 3.5 litre engine with a wide bore and a short stroke configuration which is often called an M90 (although in fact it is a type of M30). At that build date with that manifold on it ought to have Motronic engine management with a -002 ECU.

These series 1 cars have very few parts in common with the later ones; the chassis underpinnings went from being based on the E12 five series to the E28 five series after 5/82 and hardly anything (the glass, the seats, the body shape being exceptions) was retained.

cheers
Thanks for the advice. It with that in mind it looks pretty genuine. Just need to pick it up! Hope it's not a project too far...!
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tschultz
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Re: Is this an M30 or M90?

Post by tschultz »

Motronic sensors plus brake booster indicates it could be an M90. If waterjacket and L is not present, ECU/AFM or a look at the pistons would be the only way to tell for sure.

My '81 Motronic sensors had a different bracket, but maybe RHD and LHD are different...
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Re: Is this an M30 or M90?

Post by bpoliakoff »

Questionable without knowing manufacture date is the bracket from the manifold to the head holding the two sensors from the bell housing. All of the basic motronic sensors brackets I have seen use a totally different bracket..unless yours is a red headed step child Realoem shows me to be correct..My 81 does not have the water jacket but is an M90 as proven when opened up for the rebuild and of course did have the infamous white "L" Another way to tell if the motor is original is to look at the "flat" above the starter motor and see if the vin # stamped there matches the vin on the firewall and the registration which it does on the early car. The bracket holding the sensors as said by myself and Tom is an immediate alarm.
Last edited by bpoliakoff on Mon Dec 24, 2018 5:06 pm, edited 1 time in total.
81 Euro 635 M90 with motronic. Currently under a complete nut and bolt restoration. Pictures at
flickr.com/photos/bertsphotos.
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Jono B good
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Re: Is this an M30 or M90?

Post by Jono B good »

Please, please upgrade your picture taking device. It will us help you. Thank you. :D
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janusz200
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Re: Is this an M30 or M90?

Post by janusz200 »

Here you have few pictures of my M90. I hope they are of help.
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M90 block 1.jpg
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M90 block 4.jpg
M90 block 4.jpg (198.91 KiB) Viewed 7893 times
1980 635 CSi EU
M90/L-Jetronic/manual
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Re: Is this an M30 or M90?

Post by bpoliakoff »

An 81 M90m will not have the same block. It will not have the raised water passage as shown. The 81 M90 is different in this respect. I have one that is original and know this for sure and from at least a dozen other owners of 81 model year cars I have met over the years. The "L" should be there , maybe hidden by grease, but the paint they used seems to stand up. Other than that they look like any other M30 engine and are hard to identify without pulling the head. Look for the vin to be stamped on a "flat": above the starter which will show you the engine is original to the car which will be a good indicator it is an M90
81 Euro 635 M90 with motronic. Currently under a complete nut and bolt restoration. Pictures at
flickr.com/photos/bertsphotos.
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Re: Is this an M30 or M90?

Post by Pasocb »

My 12/1981 build date 635 has the “L” painted between the upper freeze plugs basically centered on the engine. It’s almost impossible to see when everything is assembled. As previously mentioned, you have the original M90 if the last digits of the Vin match the numbers stamped on the pad above the starter.
C09948BE-9ED5-48F8-B452-32A73FE0AD85.jpeg
C09948BE-9ED5-48F8-B452-32A73FE0AD85.jpeg (754.89 KiB) Viewed 7856 times
1981 635 Hennarot
1980 635 Polaris (Project)
dave9118
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Re: Is this an M30 or M90?

Post by dave9118 »

Thanks to everyone for their well informed advice. I'm going to look at the car this weekend, so hopefully I'll get some pics and load them on here.

The picture I posted is from the advert and not the best, but was rather there for reference purposes.

Appreciate all the assistance :)
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Re: Is this an M30 or M90?

Post by Sechserreihe »

What's one of these M90 engines worth? I picked up a Euro parts car from a forum member that I'm parting out. He gutted the interior and sold the dogleg Getrag and LSD but left a good running M90 in the car. It's a '79 with the infamous white L stamped on the block.
I bought the car for parts...I've got an E12 Euro conversion myself that's all done but would like to know what a good running M90 is worth in the bimmer community. I know they're rare and don't come up for sale very often. The car itself is for the most part rust-free. A few spots here and there but would make a great track car or solid starting point for a resto.

Thanks,

Mark
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dave9118
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Re: Is this an M30 or M90?

Post by dave9118 »

Sechserreihe wrote: Fri Dec 28, 2018 5:34 pm What's one of these M90 engines worth? I picked up a Euro parts car from a forum member that I'm parting out. He gutted the interior and sold the dogleg Getrag and LSD but left a good running M90 in the car. It's a '79 with the infamous white L stamped on the block.
I bought the car for parts...I've got an E12 Euro conversion myself that's all done but would like to know what a good running M90 is worth in the bimmer community. I know they're rare and don't come up for sale very often. The car itself is for the most part rust-free. A few spots here and there but would make a great track car or solid starting point for a resto.

Thanks,

Mark
You're lucky yours is so clean! I just bought that '81, but it was touch and go. The body is pretty rotten and needs a ton of work. If it wasn't for the M90, dogleg box and diff I'd have walked away.

Will be interesting to see how bad it is when I start stripping (it down).

I'll post pics when it's deliverd (or dragged).

I'm not going to lie boys and girls... she's not pretty! :(
"The explanation you are about to give, needs to be.... PHENOMENALLY good"!

Edmond Blackadder
dave9118
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Re: Is this an M30 or M90?

Post by dave9118 »

Update:

Found the big 'L' on the block. It is what it says it is!
I've bought it today, but it's a borderline basket case. When I get it back I'll have a better look, but it's touch and go.

Thanks to everyone here for the great advice! :)
"The explanation you are about to give, needs to be.... PHENOMENALLY good"!

Edmond Blackadder
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