Can Someone check My Head

[Dionk]

So my car came with an e12 head that was cleaned and machined. Seems the valves and springs have also been installed.

 

i took a few measurements nothing under 128 - slight variation from one end to the other.

 

I read a bit in this thread,  which I thought was helpful, but still made Head hurt (pun intended).  

 

https://www.bmw2002faq.com/forums/topic/224092-e12-head-milled-to-1276mm-still-usable/?tab=comments#comment-1269640

 

Also, i have a billit 090 (284) cam and rockers to install and I just ordered dual weber 40s.

 

i don’t know what kind of pistons my current engine has.

 

I’d like to build this the rest of the way myself but am a bit worried about this task having never done it. 

 

here are the pics

 

comments welcome.

[Simeon]

What head are you currently running (that’ll give us an idea of what pistons you may have)?

[PaulTWinterton]

Isn't 128.5mm the minimum before alterations need to be made? Thicker head gasket?  Or is that just for tii piano top pistons?

[irdave]

Dude.  You can totally do this.  I just did my first one.  It's a little bit of a pain in the can, there will be a bit of assembling and disassembling- just the learning curve- you'll probably do it a couple of times before it's right- just plan on it.  Those clamper guys aren't stock.  Pull the valve cover off your current engine so you can start to understand how it goes together.  I needed to make a tool to be able to rotate the cam while I was putting it in and while I was adjusting the valves.  (Do NOT clamp the head via the head gasket to the block before you check and set the valve clearance.  Sometimes it has to come back off and go back to the machine shop...)

 

But yeah, need to make sure everything is compatible (pistons / head.)

[Solarphil]

My brother!  I am you, you are me!

 

Welcome to the insanity

 

Seriously though, it can be done, my head had a heavier cumulative cut and so far things are working (knock on forehead).  If you picked up the head as-is, don’t know the machinist and are measuring even the slightest difference in dimensions from end to end, I’d take the time to cc each cylinder (google it or check YouTube).  

 

Clay the valve clearances following the recommendations Toby and Scoob made in my earlier post.  

 

I got an adjustable IE timing gear (also because it’s a better deal than the OE one) but on my tii I’m currently running it at the 0 advance mark — not to say a bit of advance might be better, but right now, on my engine, it seems to work best (but then again, I’ve heard the tii works best when stock).  YMMV.

 

Work on your back and core muscles, as you’ll be putting your head on and lifting it off many, many times over the next few days.  

 

Enjoy.  When you’re done, you’ll be able to sit back and say yes, I made that run and it sings.

[Dionk]

4 hours ago, Simeon said:

 

What head are you currently running (that’ll give us an idea of what pistons you may have)?

 

So the. Engine is a 2litre from 1968 according to the vin on the block.  121ti is stamped on the head.

 

i just read in another thread that I may have the Bathtub style pistons that early cars, normally matched with 121 and 121Ti heads)

 

 

Assuming that’s the case, can I use this e12 head with those pistons and is the head over machined?

 

Edited August 8, 2018 by Dionk
Clarity

[Dionk]

4 hours ago, PaulTWinterton said:

Isn't 128.5mm the minimum before alterations need to be made? Thicker head gasket?  Or is that just for tii piano top pistons?

I found these two picture from an earlier thread that may help answer part of this.  

[Simeon]

So the E12 head won’t naturally work with the Bathtub 121 pistons. So that commits you to either new pistons (recommended) or a horrible job of grinding head and / or pistons to fit (not recommended). 

 

The slight under sized sized nature of it isn’t necessarily a problem assuming that it wasn’t initially warped so badly that the cam journals are out of line. A few recent posts on that subject. 

[Mike Self]

And regardless of which head you end up using, don't forget to have the upper timing chain cover machined so that its lower mating surface is flush with the head's mating surface when bolted together.  Otherwise you'll have a significant oil leak in this area.  Most machine shops don't know to do this unless you tell 'em--and bring the part in with the head.

 

mike

 

PS--AFAIK the original pistons for a 121 head are NLA...

Edited August 11, 2018 by mike

[Hans]

2 hours ago, mike said:

And regardless of which head you end up using, don't forget to have the upper timing chain cover machined so that it's lower mating surface is flush with the head's mating surface when bolted together.  Otherwise you'll have a significant oil leak in this area.  Most machine shops don't know to do this unless you tell 'em--and bring the part in with the head.

 

mike

 

PS--AFAIK the original pistons for a 121 head are NLA...

and bring the bolts to attach the cover and remind them of 8 ft lbs max.

[AceAndrew]

Great points all around.  As Simeon says, you need different pistons if you want to run that head.  You're after the "piano top" pistons.  Does the cam slide into the head easily?

 

I wrote this intro to cylinder head rebuilding a while ago, it's written for a first-timer trying to understand the basics.  However, the bottom note about head thickness and it's effect on cam timing is nice.

https://adamsautosport.com/bmw-m10-cylinder-head-rebuild-introduction/

 

In addition, here's a visual on the head types/piston types.

https://www.bmw2002faq.com/forums/topic/140561-difference-between-e12-and-e21-heads/

 

Another note on those rocker locks, make sure you leave a little space (.01) between the lock and the rocker.

If you are unsure on the piston/valve clearance with that head and whatever pistons you go with, don't hesitate to clay the pistons.

You've got this, just need to tackle the bottom end.

Edited August 8, 2018 by AceAndrew

[echappe]

Make sure you align the oil passages in the rocker arm shafts correctly or you will get more practice putting it all back together!