M72 DOHC 48-valve V12 engine

Searching in my old archives I found some nice info from MWrench from 2005, might be interesting for the tech interested here:

What Korman uses is the S70 block that is 5.6L

There are three variants of the V-12. The M70 which is 5.0L and is rated 296 HP, foound in the E31 and E32 series, then there is the M73 engine which is 5.4L and rated 322 HP, found in E31 and E38 series and had OBD II Siemens Electronics, Lastly there is the S70 engine which was in the E31 850CSI only and rated 380 HP.

All V-12s that were for production use were SOHC, had an Alusil block, there are no performance cams for the M73 engine only the M70 and S70 engines. The M73 had roller finger followers to actuate the valves and are NOT backward campatible and will not work in the M70 or S70 engine. The M73 had oil squiters to cool the pistons and also had knock sensors and a misfire detector.

The heads for the M73 are slightly different from the M70 and S70 with the cam bearing diameter very small to reduce friction as well as the cam is a hole shaft with sintered heat shrunk lobes. The exhaust port (M70, S70, M73) is probably one of the worst I have worked with and will not flow, after market exhaust will not wake this engine up.

If you try to bore this engine, you will have to sleeve it and the maximum bore is 86 mm, You can get stroker cranks but very pricey around US$4000 you can go to 86 mm and with lots of block work go to 87, at 86 mm bore and 86 mm stroke you will be right at 6.0L and at 86 mm bore and 87 mm stroke will be at 6.1L

Blocks and pistons are available from BMW in all variants as well as "short engines" which we refer here as long blocks.

The F1 one engine or parts are NOT in any way compatible with the production V-12 and the only thing in common with these engines are the bore spacing.

Now for the zinger! BMW did play with a DOHC engine that was called the M72 engine, not much is known about this engine and it never reached production. This is a picture and statement from the BMW Dimensions book "The History of Engines-Engines that Made History" by Dr. Karlheinz Lange.