gemellocattivo.com

I guess the hard part is getting the information, we can't just borrow a McLaren to see what they did.


But, yeah, this has been a fantasy of mine for years: an E31 with a F1-ish engine and manual gearbox.

There are plenty of photos of the S70 on the interwebs...

Here's an article on the engine that appeared on the Hagerty website this morning, It's mostly about the M8, but does discuss the S70/1:

https://www.hagerty.com/articles-videos/articles/2019/03/20/one-off-bmw-m8-prototype-engine?utm_source=SFMC&utm_medium=email&utm_content=Daily_News_Friday_March_22

I've had a 1991 E31 with an M70 for about 25 years. Great engine for longevity and reliability. Separate fuel pumps, MAFs, ECUs, and drive-by-wire throttles. There is a limp-home mode if something fails on one bank of cylinders. I once lost a crankshaft position sensor, and the heavy car would still do 70mph on one 6-cylinder bank. I've got 170 K miles on the car and it still runs very well.

The lower end is bulletproof, the big problem is the heads, specifically the exhaust ports, which are very restrictive and can't be ported due to the position of the water jackets. The S70/1 uses a completely new head - DOHC vs. SOHC, 4-valve vs 2 valve, and much better breathing.

Later BMW engines, like the S50B30 used in the E36 M3 have all the breathing goodies, DOHC with VANOS, great port design, etc., but the cylinder spacing is all wrong.

Of course, for a guy with your skills it would be a cakewalk...

The small sixes and the M70 family have the same bore centers. 91mm, IIRC.

BMW used the same cylinder head casting on both banks, but different end caps to differentiate them left from right. They did the same with the intake manifolds. The plena were open at both ends; one end received the throttle and the other a block off plate.

In theory, the small six heads, including the S54's factory CNC ported monstrosity should bolt up to the M70 block. The difficulty is that there's only one side available from the factory. Options are to modify the head to accept the timing drive at the other end or modify the timing drive so that there's a timing drive for one bank at each end of the engine. Porsche did this with the M96, which spawned the need for the now infamous intermediate shaft bearing.

If Mark did the latter, he'd take the drive off the center like Cizeta-Moroder did.

However, if you want a quad cam BMW V12... just buy one. The 6 liter unit introduced in the E65 7 series has 4 cams, 48 valves, fully variable intake manifold and makes 450 HP. It was the first application of Valvetronic technology, which makes swapping a bit funky. The Valvetronic can be disabled and the engine run with conventional throttles, HOWEVER, swapping Valvetronic-enabled N52 six cylinder engines into E30's is becoming a thing and it may be possible to run the V12 on dual N52 ECU's the same way the M70 was run on dual 6 cylinder Motronic units.

I don't want "a" V12, I want the engine from the McLaren F1.

I have an S50B32 already but that's just half the job