NullZwei

Difference Between E12 And E21 Heads

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This is great information! I am curious now.

If there was to be a recommendation of pistons for a '76 e21 head m10, what would it be?? Flat top and call it a day or higher compression domed?

If you're thrilled by some combination of (a.) originality for '76 U.S. models and/or (b.) a need or desire for a regular fuel car -- as opposed to a premium fuel car -- then you should opt for the original flat-top pistons: they work well. But if you want more horsepower and torque, while possibly improving the car's gas mileage, and are ready and willing to commit to premium fuel, a higher compression ratio is the way to go. Your decision!

Steve

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i mean if your starting with the eitehr the 121, E12 or E21 head. That includes machining and porting considerations. i believe that the brisbane show you recommended getting a later model head? E12?

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(edited)

I wasn't up at Brisbane (though it would have been nice).

 

First I'll EMPHATICALLY EMPHASIZE, choose whichever head is thickest, has the least amount of corrosion, and has been pressure tested.  That trumps all other considerations.  Theoretically this means a later model head would be have a higher chance of being in better shape.  The later heads flow a hair bit more in stock form (but if your doing porting then its once again a toss-up),  this difference would NOT be noticeable unless on a race engine (which again, you'd be porting so it becomes a toss up).

The combustion chamber is also a bit more efficient on the later heads, but unless you're going over 10.5:1 compression and plan on running race gas it wont matter to you.

 

 

EDIT: Someone here pulled these flow numbers for reference, they seem to have disappeared in the FAQ crossover.

 

Some flow numbers in CFM @28inhg

121 head (with large valves)
Valve lift___intake_____________exhaust
.1________73.5_______________51.5
.2________113.5______________92
.3________146.5______________127
.4________173.5______________145
.5________188.5______________153

E12 head
Valve lift___intake____________exhaust
.1________63_______________57.5
.2________105______________98.5
.3________148______________124
.4________179.5____________137.5
.5________193______________143


E21 2.0 head (e21 cars and some very late 2002)
Valve lift___intake_____________exhaust
.1_________66________________54
.2_________115_______________95
.3_________155.5_____________126
.4_________179.5_____________142
.5_________190_______________148

1.8i head (e21 and e30)
Valve lift___intake____________exhaust
.1_________66________________50
.2_________111_______________87.5
.3_________155.5_____________111
.4_________182.5_____________136
.5_________193_______________143

Edited by AceAndrew

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Hi Folks -

 

I need to calculate the compression on a 2L tii engine with E12 head and EU grand piano (6,6mm) pistons.
Does anyone know how many cubic the EU grand piano on the pistons fills?

 

Does anyone know the answer?

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Hi Folks -

I need to calculate the compression on a 2L tii engine with E12 head and EU grand piano (6,6mm) pistons.

Does anyone know how many cubic the EU grand piano on the pistons fills?

Does anyone know the answer?

The compression ratio should be 9.5/1.

Anything more accurate than that would require you to measure YOUR pistons and YOUR head.

But I am sure someone here can measure theirs if you just want an estimate.

Regards

Jacques

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Guest POKTROKT

Bringing this back from the dead, I have a bone stock E21 head with 44mm intake valves, from all I've read it should have 46mm intake valves... car is from California. 

 

Anyone heard of this before?

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(edited)
1 hour ago, Guest POKTROKT said:

Bringing this back from the dead, I have a bone stock E21 head with 44mm intake valves, from all I've read it should have 46mm intake valves... car is from California. 

 

Anyone heard of this before?

 

Is it an E21 head for a two-liter engine? The only ‘02’s that were factory-equipped with an E21 head were ‘76 U.S. 49-State versions, originally emissions-legal everywhere but California and, I believe, some 1502 models — the 1502 sub-model never having been imported by BMW to the U.S.

 

How about a photo of the head’s cast-in identification and casting date? Below is a photo of my ‘76’s original head, a two-liter E21 head (“E21 2,0”) cast in April 1976 (4 nubs surrounding “76”).  These cast-in markings appear approximately between the cylinder 3 and 4 intake ports.

 

Regards,

 

Steve

 

2430FBC1-DE70-4E85-966C-4C61C8F3A25E.jpeg

Edited by Conserv

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Thanks Steve!  I misspoke above, the head is an E12.  It should still have 46mm valves.

 

Checked the head markings and found something interesting.  The head is marked with a 78 but my car is a 76

 

Have a look at the pictures below, looks to me as if the head was fitted with the wrong valves.  The witness marks on the valve seats and the valves suggests the valves are smaller than they should be.

 

IMG_4042[1].JPG

IMG_4045[1].JPG

IMG_4050[1].JPG

IMG_4054[1].JPG

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(edited)
On 4/2/2018 at 10:01 PM, POKTROKT said:

Thanks Steve!  I misspoke above, the head is an E12.  It should still have 46mm valves.

 

Checked the head markings and found something interesting.  The head is marked with a 78 but my car is a 76

 

Have a look at the pictures below, looks to me as if the head was fitted with the wrong valves.  The witness marks on the valve seats and the valves suggests the valves are smaller than they should be.

 

IMG_4042[1].JPG

IMG_4045[1].JPG

IMG_4050[1].JPG

IMG_4054[1].JPG

 

Interesting, Mario.

 

An E12 replacement head cast in January 1978.  I say replacement head because I’m not aware of any new 1978 model using an E12 head — which may simply be my ignorance.  (What head would a carbed, Euro-spec e21 car, e.g., a 316 or 318, have received from the factory?)

 

But, yeah, unless the E12 Head was being used in some Euro e21 cars, what happened? Was it an absolutely bare head and they either mis-ordered valves or had some 44mm valves lying around and decided to use them?

 

I’m guessing you’d like to install the correct 46mm valves?

 

Regards,

 

Steve

Edited by Conserv

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Good point the timeline is strange.  The history of the car is unknown, someone may have rebuilt it at some point and installed the wrong valves.   If nothing else this is proof that it can be done, car ran fine and engine seemed to have plenty of miles on it.

The head currently in the car is an E21 and should have 46mm valves so I plan to use those. 

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I really looks that wrong size valves were installed. Unbelievable! Seems there is carbon build-up all through the seat surface where the contact to valve should be and it touched just at the edge of seat.

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