121T HEAD with cracks

[Vetle]

Hi!

I am building a Tii engine. There were some cracks in the head which is probably why the engine was removed from the car in the past. 
The 121T 1975 head had a crack between the valve seat and the cooling channel (exhaust side). 
I welder I know welded the cracks, but Iam not 100% comfortable because of small holes and suddenly another crack. 
Have some of you successfully welded a cracked head? Is it worth the work and money?

 

[stephers]

Get it pressure tested but usually with this many cracks, there are probably cracks there that you don't see 

 

Thanks, Rick

[tech71]

I wouldn't waste my $$$ pressure testing that one, find another and pressure test it.

Edited April 24 by tech71

[TobyB]

As reluctant as I am to throw things out,

 

something has happened to that head.  It looks far more porous than most 1975 castings 

from BMW do.  The water jacket crack looks pretty straightforward, but the 

way it cracks suggests that there are voids or contaminants in the casting.

Or that water was used instead of coolant.  Or both.

 

As always, with heads, you have to evaluate what you have,

and what options you can find that might be better.

If you already have several thousand into porting, then fix it.

If it's just a stock casting that's already been cut 0.750mm, then

going shopping's an attractive option...

 

t

 

[Son of Marty]

If you look closely at your last picture just above the  weld repair it looks like a small crack is just forming there are probably more you can't see, as Toby said the first step is to measure the head thickness to see how much it can be skimmed. If I were to guess I think someone along the way put cold water into a hot engine causing the cracks.

[Vetle]

@Son of Marty yeah, that crack was made after the weld unfortunally.. 

I have bought another head, a 121, so I will probably use that instaen..

 

[Zak]

Throw it away or use it as a large paper weight. Not everything that came from BMW is good. I have a"118" head from a 1600 which is really porous. It's like an aluminum sponge. All the other heads I have from BMW are smooth, dense castings. Some of their imperfect castings slipped through the QC check.