how do i check an M70 ?

[!kid]

there is a chance i may pick up a M70(V12) this weekend from a local yard

you guys have any tips on how to check if the motor is any good ?

[Adrian_Visser]

I can tell you without looking at it that it is a POS, just because it is an m70. Other than that the only way to tell much about it is to do a compression test, also pull the plugs have a look at them, you can buy a cheap ass boroscope from some autoparts store to look into the cylinders with or you can just use a flashlight and your naked eye. If the engine is already out of the car good luck doing a compression test on it, also you could consider bringing a charged battery with you if the engine is still in the car. I know next to nothing about these engines but I have heard that the intake Manifold has special gaskets that always leak and are $$$ to replace . Also I believe that the Intake manifold itself sometimes cracks at the back of the engine.

[PaladinReed]

I have never heard a single good thing about this powerplant either. Top of the line technology from an antiquated time = major headaches. Hard and SUPER pricey to keep running. Imagine an e39 M60 with its problems on crack. But it has been done. Even in an e30. With turbo's if I remember right. Good Luck!

-Paladin

[quickervicar]

I've come to the conclusion that to drive an M70 is to love an M70, and to own an M70 is to loathe an M70. I've had the pleasure of driving one. And I still want one.

[OrganicMechanic]

the design is basicly 2 m20 mounted together. it is just the shear amount of electronics that makes them problematic. 2 sets of everything a m20 has including 2 ecus.

[TexasTerp]

I guess the biggest question is under what conditions are you buying the engine? Is it a junkyard engine, a craigslist ad, or a friends 750? I've seen pics/vid of 2 e30s with m70s in them and it's a crazy modification. I contemplated building a m70 e30 last year since I had lines on 3 engines w/trans but I will tell you this it will cost thousands to rebuild correctly and the weight distribution is insanely off. If you have 10-15K available to do the build correctly then I say go for it and own a very unique e30. But if you don't have the time or money to do it right, stop right now, turn around and walk the other way, don't even think about it.

[TexasTerp]

the design is basicly 2 m20 mounted together. it is just the shear amount of electronics that makes them problematic. 2 sets of everything a m20 has including 2 ecus.

This isn't true actually, it has 4 ecus not 2, and it's a single block like the m60 not two m20's mounted together, the cylinder heads aren't even the same, there are actually very few parts that are the same as the m20.

[lifeiskaos]

if you're going to do a compression test at the scrap yard, bring some oil. they drain all the oil before they put the cars out, so you dont want to crank the engine dry.

if the car has low miles and looks like it has been taken care of, you should be ok. you want to find the reason the car is there though. ideally it's totalled, but a bad transmission could also be the case. in any case, i always stay away from cars with no body damage, whenever i pull an engine from a scrapyard

[OrganicMechanic]

This isn't true actually, it has 4 ecus not 2, and it's a single block like the m60 not two m20's mounted together, the cylinder heads aren't even the same, there are actually very few parts that are the same as the m20.

wiki on m70

• Displacement: 5 L (4988 cc, 304 cu in)
• 12 cylinder V-arrangement 60 degree
• 24 valves
• Compression: 8.8:1
• Stroke/Bore: 75 mm (3 in)/84 mm (3.3 in)
• Firing Order: 1-7-5-11-3-9-6-12-2-8-4-10
• Separate twin-ECU engine management (each one for each bank)
• Max power: 220 kW (295 hp) @ 5300 rpm
• Max torque: 450 N·m (332 lb·ft) @ 4000 rpm
• Max rpm: 6000–6400 rpm *Gearing

M20 bore and stroke-- 84 mm (3.3 in) bore, and 75 mm (3 in) stroke.

e32 site


When it comes to maintaining the V12, alot of people are thinking that the 750 needs specific 750 parts, when it's comes to the engine. That isn't the case.
Basically, and some people are not gonna like this, the V12 isn't really anymore than 2 M20 engine's welded together and by coincidence are sharing the same crank. To ensure that always 1 bank will run in case of a failure, every bank has his own injection and ignition system.
That means the V12 has 2 fuel pumps, 2 fuel filters, 2 separate rails with injectors, 2 cats, 2 lambda's (o2) sensors, 2 distributor caps, 2 rotor arms, 2 airflow meters (also known as MAF's), 2 crankshaft positioning sensors, 2 cilinder identification sensors, 2 intake temperature sensors, 2 coolant temparature sensors (and 1 in addition for the EML, making it 3 in total), 2 sets of spark plug wires, 2 air filters, 2 throttle bodies, 2 camshafts and last but not least: 2 DME Motronic computers. Even the oil pump is a tandem-type. The only part both banks share are the EML computer (basically a computer which synchronize both banks), timing chain, oil filter and the part of the exhaust system after the cats. And all of that for the price of one car.....sounds like a good deal isn't it?
It's this kind of redundancy which makes your car reliable, in that way that when 1 particular part fails (for instance, a fuel pump) you often can drive further with the other bank. The EML computer recognizes a difference between the banks and is shutting the troublesome bank down. Remember, we are talking about 1988 (even 1987 in Europe) when this boeing_on_wheels is introduced.....pretty impressive....
It's also this redundancy which makes it an expensive car to maintain. Buying 2 distributor caps, along with 2 air filters can make it a hefty maintenance interval due to the costs.
Fortunately, because of the similarities with the M20 engine a lot of 750 parts are interchangeable with parts from other bimmers. I tried to make a summery of all cross-references with parts you can use from other models. Most of it tested on my own 750. Hope this can be of any help.

coloown 750. Hope this can be of any help.

[F34R]

I can tell you without looking at it that it is a POS, just because it is an m70. Other than that the only way to tell much about it is to do a compression test, also pull the plugs have a look at them, you can buy a cheap ass boroscope from some autoparts store to look into the cylinders with or you can just use a flashlight and your naked eye. If the engine is already out of the car good luck doing a compression test on it, also you could consider bringing a charged battery with you if the engine is still in the car. I know next to nothing about these engines but I have heard that the intake Manifold has special gaskets that always leak and are $$$ to replace . Also I believe that the Intake manifold itself sometimes cracks at the back of the engine.

Idiots post some funny stuff.

[Savagefurai]

Personally never driven or owned an m70 but the idea of this in an e30 kinda gives me a chubby...

Sent from my SAMSUNG-SGH-I747 using Tapatalk 2

[E30 Wagen]

It's been a dream of mine to swap a tarbo'd one into the cheapest e24 I could find for some senseless hoonamagoonagins

[Swanny]

Go this route

:)

Cheaper and easier ways to get 300hp in an e30. Granted the m70 is a VERY cool engine, the practicality is just not there. Of course if you have the budget please to a thorough build thread!

[george graves]

if you're going to do a compression test at the scrap yard, bring some oil. they drain all the oil before they put the cars out, so you dont want to crank the engine dry.

Eh - I don't think a few slow revolutions under no load would really be a problem at all.

[slammin.e28]

Lets put it this way.

840i > 850i.

Sure, it's nice to have 12 cylinders, but really, it all comes down to how much work you want to put into it vs how comfortable you are with the size of you penis.