School Me on M30 Heads

F4F9935E-5E3D-4CA5-B38C-7D61C095CE5F.jpeg
The chart is wrong.
Use the bmw factory technical info.
 
Pistons


The etk says...


11251261970
Csi

11251261954
Cs euro

11251261948
Cs USA


 
ClayW said:
This is all fantastic information.

According to this table https://motor-car.net/bmw-engine/item/16041-m30-engine , the B30 had 9:1 compression in al three forms. All three have the same bore and stroke (89x80). Would a head or piston difference be the cause for differing compression ratios in Euro vs USA motors?

Side note: my block has flat top pistons, if any info can be gained from that. I also confirmed the bore and stroke. Strangely, the block has no serial numbers; just two Xs.
Click to expand...

Disclaimer, I’m not an expert on this stuff, I’ve only driven the high compression euro B28 in my 2800CS.

I wouldn’t waste your time with a 3.0 block if it isn’t the original block. I don’t know your end goal or your budget, but a 3.0 will only be good if you stick with original carbs, or go fuel injection with a custom EMS. As @sfdon mentioned all of the other factory computers won’t align to an injected 3.0 requirements. Perhaps there is an early L-Jet 3.0 option, but again why bother.

This is my personal 12v motor swap priority:

1. M90 - Megasquirt, cam, etc.
2. M30B34 Euro - Megasuirt, cam, etc.
3. M30B35 - US Megasquirt, cam, etc.
4. M90 - Factory EMS (note there are two options)
5. M30B32 - Megasquirt, cam, etc.
6. M30B32 - Factory EMS
7. M30B34 - US Spec, Megasquirt, can, etc.
8. M30B34 - US Spec, Factory EMS

You have some cheap, readily available options in that list. Asking an engine builder (like @sfdon) if you should install a 100K+ mile used setup is like asking a dentist if you should brush before bed. You know the answer before you ask.

If you are a DIY guy and you don’t mind potentially breaking down on a club run, then you can buy a good motor with a car wrapped around it for $500-$1,000. Members like @Mike Goble with permanent dirt under their fingernails come to mind. You can replace your motor every year for 10 years and come in under a rebuild. This setup has questionable resale value, and real risk of future problems depending on what you start with. A big part of installing a newly rebuilt big six is taking-your-coupe-to-the-next-level. If done right, I think it is an investment. The Granatrot sale on bringateauler is a good example of that IMO.
 
Great. Thanks for the info, guys.

I see that I have a 25k mile 3.0 block with 8.0:1 compression, based on the flat tops. The good news is that it was free. I’m not concerned with investment, but it’s good to know what’s worth bothering with doing.

I currently have a seemingly solid 2.8L in the car, which I’ll hopefully be converting to L-Jet soon. The 3.0L bottom end is, in my head, a backup plan. I started this thread trying to figure out some options, and I think we’ve uncovered some.

Thanks, guys!
 
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