engine and drivetrain head rebuild

[PetrolJunky]

Hello,

I have a nice shop that will rebuild a 121 head for me.

It is pretty beat up and the valves are leaking.

He normally builds Alfas and suggested I bring him the parts instead of him sourcing them all.

Is there a good quality complete parts kit somewhere?

Thanks for your help.

Stock 75 2002

Matt

[danco_]

You should confirm what head is on that car. My guess is it's an e12 head or even and e21 head. 

A 121 head would require different pistons altogether, iirc. 

[PetrolJunky]

Oh hi Danco.

Okay, I was going to get a 121 and I thought I could slap it on.

How about just the stock head then

[Mike Self]

When I re-did my E12 head some years ago I bought Ireland's stainless steel valves, and they've proven to be very good--nearly 50k on the rebuild and all is well.  Also suggest sourcing the valve guides and stem seals as used on the E30 M10 engines.  They seal much better than the design used on the 2002s, which are notorious for allowing oil past 'em, causing smoking on the overrun.  

 

It goes without saying that you should replace rocker arms and shafts unless your engine has very low miles.  

 

I'm sure others will have some good suggestions too.  And...if you want a bit more performance, now's the time to add a hotter cam while the head's apart.  

 

cheers

mike

[Preyupy]

If you have domes on your pistons they need to be the correct pistons for the cylinder head (different combustion chamber shapes need different piston dome shapes or they HIT each other!!!) If they are flat top pistons you can use any cylinder head.  IF you have a 121 head you need to make sure you know what size valves you have.  The standard 121 head used a 44 mm intake valve and the 121ti head used a 46mm intake valve.  The combustion chamber is the same size and shape, they just have larger valve seats and valves. 

[percy]

Hello,

I have a nice shop that will rebuild a 121 head for me.

It is pretty beat up and the valves are leaking.

He normally builds Alfas and suggested I bring him the parts instead of him sourcing them all.

Is there a good quality complete parts kit somewhere?

Thanks for your help.

Stock 75 2002

Matt

 

 

Is the nice shop supplying the 121 head or is it yours?  Not sure what "pretty beat up" means?  Dirty, worn or the resting place for a sledge hammer?

 

Virtually any competent machinist should have little trouble rebuilding an M10 cylinder head, but regardless of competency, things often go smoother if the machinist has experience with those heads.  The same holds true for determining what parts are reuseable and having suitable replacement parts on hand.  "Sourcing" the correct parts should be easy, but too often "easy" becomes another way of saying "expensive."  Unless you know what you need and have all the parts, I would consider finding a nice shop that has ready access to parts that fit or knows where to quickly locate those parts.  

 

Like others have noted, a stock '75 would likely be using an E12 or E21 cylinder head and not a 121.  All things being equal, the only advantage of the 121 might be increased compression over the other two heads, which tend to breath better at the upper rev range.  The 121 will easily work with flat head pistons, and yes, they have been known to work with both bathtup and piano shaped piston crowns.  For obvious reasons, bathtub shape pistons are preferred for use with the matching reverse-bathtub shaped compression chambers of the 121 heads; nevertheless, in a pinch, the piano shapes will work if appropriate reliefs are cut into the cylinder head.  

 

Per Preyupy, most 121 heads used a smaller diameter intake valve, but the larger 46mm can easily be fit by any competent machinist.  Leaky valves do not necessarily indicate replacement.  They can be lapped and/or recut.  Worn valve stems are another matter, that . . . ahem . . . any compentent machinst should be able to measure.  The same goes for valve guides and seals.

[rstclark]

Just to add that it may not be too advisable to buy a lot of parts until the head has been disassembled and checked for cracks,  particularly around the exhaust ports. These heads are  now 40 years old.  I went through two heads before I got a good one to rebuild. That's a total of three.  There are mixed opinions about repairing cracked heads.  In the end the cost and risk of failure may outweigh just finding a good head to rebuild  A good machinist can tell you if the valves can be reground , check the guides  etc. and tell you what needs to be replaced. Unless you are building a high horsepower blueprinted motor, it's not necessary to get carried away rebuilding the head.  I do however like the suggestion about adding little more cam such as a 284 for a street car while you have everything apart

[danco_]

Shoot me a call if you need another head. I have a few e12 and e21 heads I can donate. I want to see your car live another day.