1982 Euro 735i donor engine identification

CookeD

CookeD

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Howdy All,

Sizing up a winter project, and have a question regarding the '83 Euro driveline that is for sale in this thread:

http://www.e9coupe.com/forum/showthread.php?t=9771

I have a complete engine out of an Euro '82 735i that had a manual transmission. I'm confused as to if it's the same engine as the M90 with a different injection, or what exactly is going on here. The injection on the '82 I have is just like this, which is Motronic 1.1?

If I enter the VIN into RealOem, there is no definitive explanation as to what the '82 735i engine is. Without pulling it apart and measuring bores, are there any identifications that will tell me exactly what I have?

Next question-- The M90 has more compression, etc... Is this an ideal start for building a hot cam / triple Webers type project, or is this not the right way to think about using the M90?

Lastly, is the M90 worth messing with in the first place, when the M30B35 donor sleds seem to be readily available?
 
The M90 makes sense if you plan to take it to a certain point. If you just want to drop it in and forget it, then it doesn't. For example, the M90 makes an excellent starting point for a performance engine because it has the larger stock bore. It is then much easier to make a more powerful stroker engine with a minimum of customization. Stroker custom parts in this case pretty much means custom pistons due to rod height differences stemming from the stroke change, and at that point you may as well sub in a B35 head to get the bigger valves since the pistons will let you set the CR anyway. Coupled with an aftermarket tuning solution (WAR chip on M1.3 or MegaSquirt) this setup should net you somewhere in the range of 230+ rwhp. The M90 is a decent upgrade by itself compared to the stock engine.

Between the M90 and M30B35 stock-for-stock, though... that is a tough choice. The M90 gaskets will be more expensive and difficult to get since it was a Euro-only deal, whereas the M30B35 was used everywhere. Most of the parts will work with each other. The M90 apparently revs a bit better since it is oversquare. The two engines should perform about the same stock-for-stock.

In terms of a hot-rod engine, the M30B35 is more expensive to stroke since it already has a long stroke, so bumping the displacement means boring, which means custom pistons again.

So, overall, I'd start with the M90, as you can grow it to suit your needs. A stock M90 will do just fine, but you have the option of stroking it and upgrading to the larger-valve head in the future. Note that the B35 head has a larger clearance volume than the M90 head, so just dropping the B35 head on the M90 will drop the CR.
 
Without seeing the vin #s of the two euro engines there is no guarantee BUT- this is how it is likely to unfold given the info so far...

the 1983 engine that is advertised here on the board is a 10:1 euro spec dirty engine.
M30 B34.
The bore is 92mm, hp is 218 stroke is 86mm pistons are "piano top"

The 1982 engine that you have would be a M90 engine 9.3:1 compression with a bore of 93.4mm and hp of 218 Stroke is 84mm

M30 B35 engine is 92mm x 86mm with 9:1 ratio and hp of 208 unless it is a euro version in which case the hp is back to218 with a ratio of 9.2:1

Headgaskets for the M90 engine are not a problem but rings are.
 
a mess I think-

How is your German accent?

http://www.online-teile.com/bmw/product_info.php?info=p251304502_11251304502-oelabstreifring.html

http://www.realoem.com/bmw/showparts.do?model=6831&mospid=47183&btnr=11_1669&hg=11&fg=20

Parts diagram
Sponsored links
No. Description Supplement Qty From Up To Part Number Price Notes
01 OIL RING 4,00MM 6 10/1981 11251304502 Cat=No
02 COMPRESS.RING 2,50MM 6 10/1981 11251304499 Cat=No, ENDED
03 RECTANGRING 1,75MM 6 10/1981 11251304496 Cat=No, ENDED
04 SNAP RING C22X1,5 ? 10/1981 07119934460 $0.35 Cat=No
06 REPAIR KIT PISTON RINGS 3,50/2,00/1,50 6 10/1981 11251278750 $81.71 Cat=No
06 REPAIR KIT PISTON RINGS +0,20 6 10/1981 11251278751 $72.54 Cat=No
06 REPAIR KIT PISTON RINGS +0,40 6 10/1981 11251278752 $72.54 Cat=No
06 REPAIR KIT PISTON RINGS 4,00/2,50/1,75 6 10/1981 11251304931 Cat=No, ENDED
06 REPAIR KIT PISTON RINGS +0,20 6 10/1981 11251304932 Cat=No
06 REPAIR KIT PISTON RINGS +0,40 6 10/1981 11251304933 $96.26 Cat=No
 
Hey Don / xAtlas,

The motor that I have is the M30B34, 10:1 euro spec.

This engine ran fine and looks great inside, but before I get started with any work, I'm wondering if there are advantages / disadvantages to using this motor as the starting point for a build.

I am contemplating either a carb or FI build, as I have a set of DCOEs sitting on the shelf, but also have all the bits from the Motronic FI. I know the DCOEs need compression and cam, so is this a good starting point for a low-buck DCOE build? Or, are there problems with detonation because of the higher compression that cannot be tuned out with running carbs?

Any help is much appreciated.
 
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