M90 questions

[mopar]

Hi,

I pulled my m90 (1980 euro Motronic 1.0) motor out of the car, for a soft rebuild (new gaskets, timing chain, ....) and I got some questions about it:
- are the valves good for unleaded fuel and LPI or do they have to be replaced?
- are the torque specs the same as for the m30 motor (head, covers, sump,...)
- I got the torque specs for an m30 head but what about all other torque specs for the motor, where can I find this info? I got the repair manual for the 1979 e24 but there is no info about the torque specs....

After rebuild this car is going to be the daily driver for my wife, so I want it to be problem free after the work is done.

Hope to find some answers here.

[86_6series]

Here are specs but I don't see M90 engine.

Still, you may be able to get some info. 2 sources same PDF

http://www.mwrench.com/Whitepapers/torqspec.pdf

https://whatismycar.com/files/bmw_bolt_ ... ations.pdf

[mopar]

Thanks for the list, will look into for the m30 engine.
Mine is m90 (m30 head on m88 block), hope the specs are the same.

Someone any info regarding the valves and fuel?

[bpoliakoff]

IIRC the last year of the M90 was model year 1981. An 88 block should not be an M90

[mopar]

My discription was not correct, it is a 1980 M90 motor, matching numbers with the car.

But still no answers to the case....

[zinnocoupe]

Good questions here.

As far as I know the valves are ok with unleaded. I've never seen anything posted that says otherwise. ive seen a few people who have rebuilt M90s and there was no mention of special valves. LPI? Propane?? No idea on that

I used the same torque number etc when I did my m90 head. and any other torque specs I just used the bentley. I didn't touch the bottom end so can't comment on that. The head gasket is M90 specific and cost more too.

I just googled "BMW M90 torque specs " and got some pretty good info, with a bit more digging you'll find the answers I think. Good luck

So I got to ask.... if your wifes daily driver is going to be an m90 powered car, whats yours??

[Pasocb]

Hi Mopar,

My apologies for chiming in late on this. As others have alluded to, you can utilize the M30 engine specifications to rebuild a M90. Basically, the engines only differ in basic bore/stroke geometry, piston crown design and cam profile.

Your question regarding our engines' suitability to run unladed fuel is a good one and has some mixed controversy due to the transition period when the cars were produced. Given the heads are constructed from aluminum with high quality steel/iron valve seat inserts, these engines are inherently better suited to running unleaded fuels. Some say that it is no problem at all, others stay that BMW changed the metallurgy of the inserts around 1985 to better run the unleaded fuel that had been prolific for quite some time by then.

When rebuilding my 1981 M90, the valve seats had almost no wear. The head is original to the car with over 100,000 miles on it. This is all empirical evidence on my end, so take it for what it is worth. We lightly touched up the seats and valves with the grinding stones prior to reassembly.

cb

[bpoliakoff]

^++1

[mopar]

Thanks for the answers regarding the valves and torque specs.

Now I am making a variant on the iron maiden tool so I can take the camshaft out and test the valves on air tightness.
Than I can take the valves out and the head can be flattened for reinstall.

When the tool is ready I will post a photo of it, it costs about € 15,00 on material and a half day work to make it, hope it works fine.

[Drew]

Be interested to see piccies of your iron maiden tool please. I tried to DIY build one also, but it was a hopeless failure! And I ended up stripping and rebuilding the head without the benefit of the tool.
+1 on what others have said, I've run an M90 on unleaded with no adverse. I currently run an E9 on unleaded and the compression is just fine, no sign of valve seat damage.

Re torque specs, I use two Haynes manuals, one for E3 and one for E12. Usually they agree. On head bolts they don't agree however, and it looks like head bolt specs for M30 engines have 'evolved' over the years.

You'll probably already know this, but don't use a M30 head gasket on a M90. M90 gasket is harder to source, but is the only option.

[mopar]

The dutch version of the iron maiden, I found this on a site of a dutch fellow but the dimensions he mentioned where wrong, I corrected them and made this in half a day, the total cost is € 27,00 including all the bolds (also the eight M12 bolds to fix it to the head).



Here you can tighten the valve springs on the inlet side first and then the outlet ones so they don't hit and bend.

[Drew]

Nice work, it's a simple design that, steel bar and angle iron, some drilling and tapping looks about it. No welding?

Is there any protection for the rockers? They're softer than the steel bolts and will be gouged (or worse) as the bolts are tightened

[mopar]

I have to make connectors so they push on the excentrics and not on the rockers, will post pictures when they are ready.
Got the materials and made them to fit, only here I got to weld.

[Pasocb]

In my opinion, this version of the tool is one of the more elegant. It has an advantage that it is adjustable for any cam profile. I did noticed that the dimensions and angles given on-line seemed a little off. Presumably something got lost in my translation?

So far I have not found a need to fabricate a tool like this. I have always been completely disassembling the head not just removing the cam. To do so, I remove one end of one of the two piece rocker shafts by loosing the rockers, removing the rocker/shaft clips and shifting the rockers off the cam lobes as needed to completely release all valve spring tension. Initially, the cam is rotated to an ideal position to help facilitate this. I do not recall if it is best to start with the exhaust or intake shaft. A quick study of the cam lobes will tell.

I suspect having a tool like this would be a time saver and could prove useful.

cb

[mopar]

This is the connector for the rockers:


The M10 bold fits in the connector:


And the connector fits on the rocker arm excentric:

[Lieuwegaal]

Good topic!

As I pulled my M90 and took it apart, I am looking into the possiblity to rebuild it myself or get it rebuild (with improvements where possible).
Loving the answers and will follow this topic untill and after I decide what to do with the engine.

Cheers!