How to: Tell what head an M20 has, the 2 second way.

[Camper Van Someren]

I found a VIN from a 1990 325i on the block. I talked to the prior owner of my car and he said he swapped in the motor, but he thought it was from a 1987. Said he kept the original 86 “eta” ECU and tried to use the new fuel rail from the donor motor but it ran like crap (probably because it was an eta Motronic 1.0 controlling a motor that should have 1.3) so he put the original fuel rail on. He also put on some pulleys and water pump from the original motor to make everything work. He said he swapped out the “2-stage” fuel pump for the newer pump. After doing some reading, it looks if I could get an ECU and engine loom from a Motronic 1.3 325i, then it would probably run better and make lots more power?

[Camper Van Someren]

So many threads. It appears you have a "cheater" motor. It's common for crap-can racing for people who "think" they are gaining by using a stock eta and adding an 885 head. Sorry to say, but a 318iS will out-rn it.... You need to decide if you are going to run the car as an eta, or 325iS, and stick with your plan. The 325iS trim will produce about 150whp/50wtq on a good JY motor.. The eta will produce about 120whp and 165wtq, also in stock "racing" form. Nearly equal on the racing circuit. That being said, the "2.7i" combo puts about 135whp and 150wtq. If you go to user settings and turn on "signatures" you will fond links to dyno trials we have done on m20's at work. https://www.r3vlimited.com/board/for...ad#post9875136

Ok I’ll have to find those threads about cheater motors and do some reading. However the car has had a whole engine replaced (not just head) so probably more likely that it is a full 2.5 from a 325i rather than a cheater. It doesn’t have a separate gear on the front for the crank position sensor (why I originally thought it was a 2.7) but maybe they are running a full 2.5 motor with the sensors and ecu from the original 2.7? Is that possible? I looked for the “serial number” stamped on the block but there is nothing there. I guess my next step would be to pull a spark plug and see what pistons it has. Then I’ll know if it’s a 2.7i cheater or a bad 2.5 transplant. Sent from my iPhone using Tapatalk

[ForcedFirebird]

So many threads.

It appears you have a "cheater" motor. It's common for crap-can racing for people who "think" they are gaining by using a stock eta and adding an 885 head. Sorry to say, but a 318iS will out-rn it....

You need to decide if you are going to run the car as an eta, or 325iS, and stick with your plan. The 325iS trim will produce about 150whp/50wtq on a good JY motor.. The eta will produce about 120whp and 165wtq, also in stock "racing" form. Nearly equal on the racing circuit. That being said, the "2.7i" combo puts about 135whp and 150wtq. If you go to user settings and turn on "signatures" you will fond links to dyno trials we have done on m20's at work. https://www.r3vlimited.com/board/for...ad#post9875136

[Camper Van Someren]

Sorry I’m reviving some old threads trying to figure out what engine was swapped into my car. If this information here is reliable then it seems I have an 885 head with an eta intake manifold. The head definitely has the 2.5/2.7 circle casting, but the valve cover has the roundel instead of saying BMW (I read somewhere that 885s didn’t have the roundel). The manifold definitely appears to be eta. Weird. Thoughts?

Never mind the more I look, that is a 325i intake manifold. I also confirmed by putting my phone under the intake manifold and getting a picture of those all-important numbers

[Camper Van Someren]

Sorry I’m reviving some old threads trying to figure out what engine was swapped into my car. If this information here is reliable then it seems I have an 885 head with an eta intake manifold. The head definitely has the 2.5/2.7 circle casting, but the valve cover has the roundel instead of saying BMW (I read somewhere that 885s didn’t have the roundel). The manifold definitely appears to be eta. Weird. Thoughts?

[meengreene30]

Those are not the intake ports of a 731 head unless it has been port matched to a 325i manifold

Porting might have been done not sure. we were stumped with this motor too, came with a 272 cam, hd valvetrain. After a lot of searching we came up with it being a modified 731. Either way i'm really happy with this setup whatever it turns out to be, pulls a lil harder than my buddies 2.7i with same cam and valvetrain running headers.

[whodwho]

Those are not the intake ports of a 731 head unless it has been port matched to a 325i manifold

[meengreene30]

My 731 head i'm running.

[702pjc]

I too have both the indentation mark and the 2.5/2.7 nub

[actletpone]

There is a head at my local bone yard which has the circle like the amc head. It does not have the other cast circle with 2.5/2.7 stamped on it, instead it has a bit like the eta at about cylinder 2 which just says 2.5. On the intake side it has 885 and the BMW enmblem. It is on a 1986 325.

What does this mean? Is it a 2.5 eta?.. can it be put on a 1990 325i ?

[blueapplesoda]

I'm assuming for those of you who have the machined down nub where it should say 2.5//2.7 or 2.5, the reman co machined the exhaust manifold mating surfaces down.

Sort of like the tell-tale casting dots on the bottom of the cylinder head, block mating surface, to tell you roughly how far the head is machined down. I believe there are 3 stages of dot depth, but I may be wrong. I have to look, i just know that once all those dots are gone, the head has been "used up".

[reelizmpro]

I have a 1989 325i, manufactured in 9/88 and my head only has the 2.5 on the circle and not 2.5/2.7. Is this the original head? or was it replaced with an older one at some point?

Probably was changed but I'm not sure of the exact cut off date. Take a pic of the engine bay for me. Does it have torx or hex headbolts?

[mr.vang]

my eta head doesn't show what you had presented

[markt51]

87-88 cars came from the factory with 885 heads embossed with "2.5" only and hex headbolts. Even if your car was a super ETA 2.7 liter. 89-on heads had "2.5/2.7". These are the original specs, so if you have an 87 325i with a "2.5/2.7" embossed head and torx headbolts you know they were changed at some point.

I have a 1989 325i, manufactured in 9/88 and my head only has the 2.5 on the circle and not 2.5/2.7. Is this the original head? or was it replaced with an older one at some point?

[reelizmpro]

Probably snapped a timing belt before or overheated.