M90 options

eriknetherlands

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So in my quest to get my car running again, I've acquired an M90 from Forum member @richard_csi who kindly offered it to me.
Block is now with renowned e9 Restorer Miklos in Hungary.
Engine # is 7400272

I'm open to opinions on what to do with the block - just throw in your experience, wisdom, and anecdotes if you'd like too.
I've read about almost all on the forum that has 'M90' in the text I think by now :-)

I want the car to be able to cruise, and manage daily traffic. I'm not after a race car experience- I'd be better of taking driving classes instead of throwing (more) money into it. But i do grin when I'm first off at the traffic lights, and enjoy a spirited drive now and then through the twisties in the Belgian Ardennes hills and the Alpes (mountains). Still, 'Elegant Sport' is what an e9 is in my view, and I want my wife to be able to drive and enjoy it too. Helps also with allocating funds :-) .

I'm desiring (i think..) an engine that doesn't look out of place in an E9, so i'll likely go for the 'Csi-look'.
As the M90 blocks regularly need new pistons (acc @sfdon who's been very helpful with tips along the way), custom pistons are already in the budget. 3,5 L is plenty for me, no need to go bigger.
So considering 10:1 compression, or perhaps even 10,5: 1. Gas quality isn't an issue here in EU (acc google Ai). Perhaps the price of pistons will force me towards std spec stuff.

wrt to the cam: the 284 Schrick cam seem to be a standard choice, though I've read some members regrinding their original cam to the same specs. Any thoughts on that anyone; pro/con? Would a 284 cam still make it a streetable car so my wife will be able to drive it? I'm not after a car that stutters and judders at a traffic light.
wrt to head choice, I'm not knowledgeable as to what head the block currently has. That'll need to be established (I'll ask Miklos and post pics here)
wrt to intake system I'd like the original CSi Looks. So that's then L-jet I think? I'm always mixing up what's what, and what will work on the head. I *think* the block has an L-Jet setup, though I'm ready to be schooled here. (again; I'll ask Miklos and post pics here) Is Motronic a sensible upgrade from D or L-jet? as it's
wrt to ECU, megasquirt, 123 ignition and other such systems; what the benefit and consequence in terms of required parts & rough cost? I'm in the Netherlands, so i am wondering if some of these solutions are "regional"; I've come to think Megasquirt is system favoured in the US< but don't see it as much on this side of the pond.

I'm considering an approach that if money turns tight, i'll nibble on aspects that i can swap/add a year later. So spending the money with a priority on the inside of the engine, then as we progress through the budget, there will be less frills on the 'outside' so to say.
As such, I'm planning to use the std 3.0 exhaust i still have; it's not new but almost NOS. If that turns out to be restrictive for the engine I can easily swap that out a year later.

Any thoughts? Spot something stupid? Fire away!

M90, confrimed by SFDon:
Possibly an M90 -zoomed.jpeg

white painted 'L'
White L painted on raised water channel.jpeg

engine #
engine number 7400272 from an 735i acc realoem -zoomed.jpeg
 
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E21 intake runners with a csi manifold would look nice and stock with a bit more airflow for the schrick cam. Not sure i would bother upgrading to motronic, a good standalone system with d jet appearance i think would look great.
 
None of your photos seem to have posted.

As you know I recently bought a rebuilt M90 with a Schrick 284 cam from SF Don. I took this plunge for two reasons: 1) Don pointed out to me that the US spec 3.0 engine was pretty weak (which is why so many folks convert to M30B35 engines and such) and 2) I have an M90 powered 1980 Euro spec 635, and I love it. Best engine I have ever driven...

I am sure you have read my opinions and experiences with this engine (funny aside...I Googled it a while back and the AI summary included some of the statements I had made about it on this forum.. :cool: )

Anyway the M90 running standard old L-Jet is a great ride. I think it runs an 002 ECU (I can check on this for you if you want). You will want to either get the AFM rebuilt or at least check it, and maybe tune up the resistor strip inside.. I would avoid a Megasquirt or other aftermarket setup unless you want to do a lot of dyno testing. The guys in Munich did their homework on the original, and it gets an A in my book.

Years ago, I ditched the Bosch ignition unit, and installed an MSD 6A ignition control unit (I know, sacrilege!) . That, Bosch Silbur plugs, and fat MSD wires seem to give this car what it likes (it also likes Toluene in the gas.. but that's because 91 octane is pretty much all that is easily available here). The MSD gives it a very robust spark.

I woudl definitely try to find an M90 head. I'd start with Don. I know he has several. The cam has a different end, and there are some variations in the cooling passages. You also cannot use an M30B35 head without changing the pistons to retain the compression ratio.. So trying to use original parts avoids going down rabbit holes chasing compatibility issues.

My 635 runs with a Getrag 265/6 overdrive trans, and a 3.07 LSD diff. As I have posted before, that's a high geared setup, but the M90 torque can handle it. In my E9 build I am likely going to use a 3.45, or maybe a 3.25, since I have no business driving the car at 100+ mph. I have a spare 3.07 with the external oil tank, and I am hoping Korman or someone can re-gear it.

Like most EFI cars, the L-Jet is very sensitive to vacuum leaks, so be mindful of hoses and gaskets... You might also want to locate a new fuel rail and some flow tested and matched injectors. AND, be sure to use the right head gasket and new head bolts...

Also get in touch with @Bert Poliakoff here on the forum. He did a major rebuild of his M90 (It is a later Motronic version), and is a wealth of knowledge about performance upgrades on this engine.

Looking forward to your progress!!
 
I believe there's a M90 / Getrag 265 / 3.07 LSD for sale in the forums:
 
The M90 Head is specific to the M 90 block.

If you don’t have an M90 Head, you can drill another head to duplicate the important coolant passages.

Failure to do so results in what are called steam holes, which is something to avoid.
 
When it arrives, I'll crack the block open to inspect what I've bought, and see what head is on. It's supposed to be block that hasn't ben messed with though the wring harness has mods in it.
I'm sure I'll bug you guys with some ignorant questions along the way.
 
I believe there's a M90 / Getrag 265 / 3.07 LSD for sale in the forums:
yeah, but that block is in the US. I'm not. These things end to sink if you stick em in a dinghy en push it towards the Netherlands.
 
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