Mikael,
Do not get misguided by people who don't understand a thing about LM002s (actually, the very most).
LM002 engine is 5.2L in displacement - with carbs and EFI.
So LM002 with EFI is a 5.2L - engine code L520i.
Carb engine is a Countach 25th derived L510 4V with heavy duty air filters.
Carb engine has 2 upper chains with manual tensioners and lower gears off the crank to drive the chains (you probably know, as you own one).
The LM EFI engine block design is Diablo-like, with 3 chains: 2 upper and 1 lower.
New engine case, Diablo style oil pump, not 2 spur gears like Bizzarrini design.
Cylinder heads are much like carb heads.
It runs clockwise, Diablo engine runs counter-clockwise - cams won't work anyhow.
I've never taken LM002 EFI engine apart, so I don't know how the lower chain and tensioners look, but maybe they are the same with Diablo - so they can tighten the wrong side of the chain. That justifies why LM002 EFI has small engine cams and real dyno never exceeded 380 hp.
LM002 EFI crank has special rod journals and special rods. Somehow they are problematic - many engines had problems with bearings or oil pump. Hard to make up for statistics, because they were occasionally driven, rarely serviced and done by people having zero understanding of how it works, because there is no repair manual at all.
First 50 engines had Diablo-style water pump, but it had too much side load on the case, so later L520i after 50th engine have a "big" water pump with 2 inner bearings (1x single row and 1x double-row bearings) and 1 outside bearing for additional pulley suspension. The outside bearing sometimes spins around and damages the case (because of an imperfect design, I repaired such)
LM EFI has additional air deceleration valve from Porsche 928 K-Jetronic system that allows smoother deceleration to idle.
Diablo EFI can cope with itself with help of ignition.
On later Diablo carter motor also aids to slow down the throttle closing, it suspends the throttle rod shaft a bit (you can hear/feel it with ignition on, opening them manually from the engine bay).
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So LM American is just pure marketing stuff:
spare tire cover, ugly side skirts and body stripes - the only differences if compared to normal EFI LM.
Anyway, what I mean is that LM is a very special car.
It's funny that it's a very small run of very different cars with many many differences - buttons, dashboards, interior boxes, fuel tanks, pedals, frame reinforcements, engines, undercovers, emission stuff, tow hooks and etc. No other Lambo had so many differences, it seems.
And so LM is pure experiment in many things.
It was a prototype for Diablo engine design and EFI.
But it has limited similarity to the Diablo itself.
p.s. Also LM002 has a disappointingly quite and high pitched exhaust note that makes me sad.
