engine and drivetrain M10 Gurus! Block & Head Identification

[s99]

Hey guys!

 

I am purchasing an m10 block and head that has apparently had prior work done to it. It is possible that work has been done by metric mechanic.

 

I am trying to figure out what type of pistons this block has and what compression ratio this engine could be. The seller says it is either 10:1 or 9.5:1

 

Can anyone shed some insight for me by the pictures posted?

 

The block is from a 1976 bmw 2002 VIN 2374167, manufactured oct 75 - dec 75.

The head is a 2.0 e21.

 

Edited May 5, 2014 by s99

[2002dean]

I considered purchasing this, but shipping costs kept me from doing so. I'd be interested in what you find.

Edited May 5, 2014 by 2002dean

[Guest_anonymous]

buried somewhere on the forum is a piston dome height chart. If the dome height is 6.8mm they are euro tii spec 9.5:1 compression pistons. The only way that piano tops will work with an e21 head is to clearance the combustion area of the head. If that's what is meant by "some work has been done," it does appear by the non uniform carbon burn area on the head deck that it has been clearance to work with piano tops. Whether it is properly clearance for these domed pistons, or if Metric Mechanic does/or did this is another question.

 

*It does not have the signature MM porting

Edited May 5, 2014 by daron_in_dementia

[s99]

buried somewhere on the forum is a piston dome height chart. If the dome height is 6.8mm they are euro tii spec 9.5:1 compression pistons. The only way that piano tops will work with an e21 head is to clearance the combustion area of the head. If that's what is meant by "some work has been done," it does appear by the non uniform carbon burn area on the head deck that it has been clearance to work with piano tops. Whether it is properly clearance for these domed pistons, or if Metric Mechanic does/or did this is another question.

 

Thank you very much for this information. Unfortunately my knowledge is limited on what work has been done to the head. The engine isnt in my possession yet so I will get more detailed measurements and pictures soon!

 

Thanks again.

[Mike Self]

And that cylinder head is either from an E21 or an E30, as the mechanical fuel pump boss isn't drilled or tapped.  Couldn't be from a tii, as there were no E21 heads used on tiis'.

 

Look at the date casting just below the "E21 2.0" marking; that will give you a clue as to its original use.  I'm guessing E21.

 

cheers

mike

[TobyB]

It's a 77- 79 E21- otherwise it would say 1.8i and be a different shape.

 

That "looks" like it's in good shape- you'll only know when you strip it apart.

 

That's not an ideal piston/head combo, but it will work just fine, if it's modified right.

And from what it looks like, it's done OK.

 

As to compression ratio- you won't know until you measure things.  Yes, those might be

9.5:1 pistons, but how much have the chambers been modified, how much have things

been decked, and how many commas can I use in one sentence???

You'll want to cc the head to make sure it was done evenly- that's probably one of the

biggest things you can do to produce tunable power.  If one bore is high compression,

you have to detune the whole motor to it....

 

Looks like fun,

 

t

[oldguy]

thought since there was no TII's the e21 pistons only came in one compression ratio.   The E12 pistons came in 2 and the 121's came in two.  while e12's look similar to e21's..  the piano is mirrored on the piston and the valve orientation is different.

 

also to note.  Since it's a 320i head, the camshaft is likely 320i and the gear on the end rotates backwards of what a 2002's is.  need a different cam or dist.

[jgerock]

Measure the diameter of the intake and exhaust valves and get close-up pics of the intake and/or exhaust ports to see if they have been modified.

[TobyB]

To me, those look like E12 pistons and the head's been modified to use them  In E12, you got at least 3 ratios that weren't

flattop.  In E21, I thought there was at least one dome... but no idea what its 'bump' would be.

 

And the 77-79 cam has the same gear as the 2002- it went to reverse rotation with the 1.8i in 1980, when the cars

went to electronic ignition.

 

But it's hard to tell based on a few pix.  I'm just making a semi- educated guess...

 

t

[Conserv]

On 5/5/2014 at 3:00 PM, TobyB said:

....In E21, I thought there was at least one dome... but no idea what its 'bump' would be....

t

 

Here's what 9.5:1 pistons for an E21 head look like (they're in my '76). The head was new and the chambers are stock.

 

Steve

 

[kbmb02]

Agree with above - the pistons in the OP post are for an 'E12' casting head. The head dome has been modified to fit, you'll want to cc and measure to determine what the C/R of the whole assembly is.

 

Here's what 9.3:1 pistons for an E21 head look like (they're in my '76). The head was new and the chambers are stock.

Steve

 

For a data point, here's what pistons for an 'E21' casting head look like when building for racing compression ratio (this is the prototype I used to spec final piston-to-head clearance, valve pockets, etc). -KB

[Conserv]

 

....For a data point, here's what pistons for an 'E21' casting head look like when building for racing compression ratio (this is the prototype I used to spec final piston-to-head clearance, valve pockets, etc). -KB

KB,

I'm just curious where your compression ratio ends up with this style piston.

Thanks,

Steve

[TobyB]

Whatever you want it to be!

 

heh

 

t

[kbmb02]

Whatever you want it to be!

 

heh

 

t

Toby's correct.

 

Some background: For the racing program, I developed a piston design for a spec block 'deck' height (which means the piston is always the same amount 'in the hole') and a spec "E21" casting cylinder head thickness (so the chamber volume is the same). Figuring a specified cam lift so the valve pockets are the plunged to the same location, the lone variable remaining is the dome volume. (note: I say 'the same' within the tolerances I find acceptable for performance and longevity)

 

Which means, I can build a set of pistons to a compression ratio of choice by having the 'peak' of the dome modified to achieve the desired dome volume (and hence, the desired compression ratio). Performance engine builders do this all the time ... this is my effort to make it repeatable, within reason. As of now, the formula has worked. (for those wondering or noticing: I have not dug deeply into piston dome shapes to this point)

 

To answer the question: 12.6:1 was the target for the piston in the photo. -KB

[Conserv]

Thanks. Very nice!

Steve