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I began teardown today on a project M10 engine for Survivor, got this engine along with some other bits from a guy up in Salem who was doing an M20 swap on a 74 2002. My plan is to overhaul and install in Survivor.

Heres what I know:

Engine VIN: 4225770, This corresponds to a 2002 manufactured 4-74.

Cylinderhead: E12

The pistons however, are not what I was expecting, Not piano, not flat. I think they are 2.0 pistons used in early  E21s, are 9.3:1 compression and .5mm oversize.

 

I'm not aware of this combination (E12 head and  E21 2.0 pistons) ever being mentioned as a workable combination?

Also does the 327 stamped on the camshaft flange have any significance? Elgin 327 cam perhaps?

Thanks in advance, Mike

 

 

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Good to know! No signs of combustion chamber modification? We know a piano top 9.5 (below) works with the E12, but now we know more!

 

The engine’s casting date is on its right side, between the first and second freeze plugs.

 

 

 

I believe I see “74” on the head, but I can’t make out the number of month nubs. The block and head may have been together since the factory.

 

Best regards,

 

Steve

 

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No apparent  mods to combustion chambers, no signs of interference between pistons and valves. 

The cylinder bores look good, no detectable ridge, still some hone marks present.

Will get the bottom end disassembled later today.

Not sure how this affects my build plan at this point, I was planning to bore the block to .5mm oversize and install a set of NOS flat tops. This blocks already at .5mm oversize.

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No month nubs clearly visible on the casting date, so probably a January 1974 head. It’s likely been with this block forever.

 

Since the block’s already been bored to second oversize, you might need to find larger oversize pistons.

 

Best regards,

 

Steve

 

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I'm not experienced enough to make statements of fact about compatibility, but can relate what I found in my engine.  It came to me from a backyard builder who did numerous unusual (wrong) things about various small details, and also this-

 

it had a 2.0 E21 block, .25mm oversize "45 deg piano top" pistons (the kind reported to have been used on E21's), and an E12 head. 

 

The pistons were relatively good shape except for the spot where valves had hit them all,  The E12 head had been modified artistically with a die grinder, sorta to match the piano tops' excursions upward.  The block had not been skimmed but the head was thin, a bit beyond minimum spec.  The (cast) pistons were unmarked except for the size, so I don't know what compression was to be expected. 

 

On the surface, this seemed to validate the common story that 45 deg piano top pistons are only good for the E21 head, but there are too many unknown variables to call it fact finding...

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8 minutes ago, Tommy said:

Well, I don't think I have but it shouldn't be hard to find.... here.

 

Its quite possible the head has been modified in some way. Thats pretty much why I started the thread, to get input/data from people.

I will get this cylinder head cleaned up and check it out more.

This greasy, cheap core engine is becoming interesting. I enjoy a mystery.

Non standard pistons, possible major head work,  wondering still about the camshaft.

Any significance to the "327" stamped on the flange? Anyone?

And yes, I know I may have to measure it to determine its specs and I will. But tapping the braintrust here ia always a good first step

Thanks for the link.

 

 

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The head's been opened up- 

if you clean up the side opposite the plug, you

should see evidence...

 

The cam numbers are from a grinder- your best bet would to be to measure it and

see what sort of lift numbers you get.  327 degrees of duration is a LOT, and that

piston shows no signs of valve contact... 

I suppose long duration and low- lift are possible, but...

 

 

The piston itself is unusual in that it has a cast- in arrow, and a center 'nipple'.

And that the lathe marks on the crown are so pronounced.

But the size marking stamp looks very similar to other KS and Mahle markings.

 

It's always fun opening up a new engine...

 

t

 

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40 minutes ago, TobyB said:

The piston itself is unusual in that it has a cast- in arrow, and a center 'nipple'.

And that the lathe marks on the crown are so pronounced.

But the size marking stamp looks very similar to other KS and Mahle markings.

I'm going with Mahle 3431-002 early 320i.

 

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Yeah they are Mahle pistons, for a Euro spec 320i. Found some supporting evidence here for that and that they will fit an unaltered  E12 head, unless Euro E12 heads were different.

They look pretty good, ring side clearance is not bad...Hmmm

 

 

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