Cracked head. Need a replacement

E3AV

E3AV

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There is some sort of grey stuff on one of the intake valves. Is this carbon build up? Why would it be in only one of them? Most of the stuff was on the valve itself.
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If it’s gray- pull the spark plug and if it’s gray and covered with thick goo- it’s oil and shouldn’t be there.
 
The spark plugs are equally black in color and dry. Some of the plugs do have oil on the threads but here I’m suspecting a leaking valve cover gasket.
 
So I did a compression check when the engine was cold
Cyl 1 : 135psi
Cyl 2 : 130psi
Cyl 3 : 175psi
Cyl 4 : 135psi
Cyl 5 : 135psi
Cyl 6 : 115psi

The high number on nr 3 got me a little bit worried so I used my cheap boroscope to take a look inside the cylinder.
I could see some droplets hanging from the cylinder walls.

Decided to pull the head off.


IMG_2511.jpeg

Don’t pay too much attention to piston 6 as I wiped it off to take a closer look.
Examined the head and found a crack
IMG_2515.jpeg


So I guess I’ll be looking for a replacement.

I also found out that the engine is actually a b30 and not a b28 by numbers on the pistons

What are my options for a replacement heads? My cracked head is stamped 76’ and have the number 1250019-9
 
E3AV said:
So I did a compression check when the engine was cold
Cyl 1 : 135psi
Cyl 2 : 130psi
Cyl 3 : 175psi
Cyl 4 : 135psi
Cyl 5 : 135psi
Cyl 6 : 115psi

The high number on nr 3 got me a little bit worried so I used my cheap boroscope to take a look inside the cylinder.
I could see some droplets hanging from the cylinder walls.

Decided to pull the head off.


View attachment 191960
Don’t pay too much attention to piston 6 as I wiped it off to take a closer look.
Examined the head and found a crack
View attachment 191959

So I guess I’ll be looking for a replacement.

I also found out that the engine is actually a b30 and not a b28 by numbers on the pistons

What are my options for a replacement heads? My cracked head is stamped 76’ and have the number 1250019-9
Click to expand...
If you previously posted the condition of your engine, forgive me for not noticing. I mention this since a cylinder head crack may have no direct relationship to the gray deposits on the intake valve. That is likely due to a bad valve seal, worn valve guide or even a worn valve stem. Your marginal compression readings also suggest a valve job was in your future. The condition of the bottom end is another matter, perhaps worthy of a separate thread.

I think your next move would be to present your cylinder head to a competent machine shop for evaluation and repair. It is difficult to assess the magnitude of the depicted crack, via long distance, but I would bet the crack could easily be ground and tig welded. Still, that is not the only consideration. If that head has been resurfaced/milled beyond recommended specifications, you need a thicker head gasket or another work-around, which is why a competent machine shop can be an invaluable asset. In the last century it might have been easier and more cost effective to locate a fully rebuilt replacement head, but times and the ready availability of replacement heads change.

Light reading: https://firstfives.org/faq/cylinder_head/cylinder_head_faq.htm

77_head_crack_closeup.jpg



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iu

iu


iu
 
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tochi said:
The condition of the bottom end is another matter, perhaps worthy of a separate thread.
Click to expand...
Could you elaborate this?

I think the head has previously been resurfaced. I think I can see traces of this.
 
Will a head from a e32/e34 m30b30 fit my engine?
Found one from 1990 with number
1708497
 
E3AV said:
Could you elaborate this?

I think the head has previously been resurfaced. I think I can see traces of this.
Click to expand...
I was referring to the condition of the parts below the cylinder head, that is, pistons, rings, cylinder walls, etcetera. Not saying there is anything wrong with those parts - especially without viewing them. Nor am I suggesting that you need any further disassembly. You may be familiar with the history of your engine, including maintenance - so that you might know what to expect in terms of reasonable wear. At least with the cylinder head removed, you can quickly examine cylinder wall condition, which, in turn, can put some concerns to rest.


In a perfect world, your compression readings could be higher and more consistent. However, those readings can easily be explained by cylinder head issues, including the discovered crack and/or leaky/maladjusted valves or a compromised head gasket - along with lower compression flat head pistons. Some of the inconsistent numbers might also be due to testing methods or the gauge itself. Most, if not all of these things can be remedied by a competent machine shop or an enterprising shadetree mechanic. Yes, your photo indicates that the head has been resurfaced. This makes one wonder why this was done, warpage due to overheating or part of a previous repair? Since the image you posted is of a small area, further conclusions are mere conjecture. Again, some of these questions are easily answered by a "competent" machinist. Incidentally, although locating another cylinder head may be the most expedient fix, there are hardly any guarantees against inheriting someone else's problem. Even if your cylinder head has been milled beyond specifications, it may still be rendered serviceable with a thicker head gasket.


iu


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Curious 2dr sedan?
iu
 
We don’t recommend early heads. And would only repair one on a Csl or Csi.

just look at yours to understand why.

look for a later head but not after 1986.
 
Nowadays I finish all the openings in the aluminium head by filing to reduce the notch effect of the edges. They are very sharp and so the possibility of cracking due to the notch is present.

Filling and sanding radius approximately 1 to 2 mm.

PS I also did a dye penetrant test on the head. Result: acceptable. :)
 

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E3AV said:
So I did a compression check when the engine was cold
Cyl 1 : 135psi
Cyl 2 : 130psi
Cyl 3 : 175psi
Cyl 4 : 135psi
Cyl 5 : 135psi
Cyl 6 : 115psi

The high number on nr 3 got me a little bit worried so I used my cheap boroscope to take a look inside the cylinder.
I could see some droplets hanging from the cylinder walls.

Decided to pull the head off.


View attachment 191960
Don’t pay too much attention to piston 6 as I wiped it off to take a closer look.
Examined the head and found a crack
View attachment 191959

So I guess I’ll be looking for a replacement.

I also found out that the engine is actually a b30 and not a b28 by numbers on the pistons

What are my options for a replacement heads? My cracked head is stamped 76’ and have the number 1250019-9
Click to expand...


I have AMC heads- NOS never installed, original and never machined.

For carb engines with mechanical fuel pump.

IMG_8475.jpeg
 

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Good to know, but I think the price would probably be out of my range.

Anyone knows if it’s possible to fit a m90 head to my b30 block?
 
M90 head has two coolant holes between each cylinder.
Your b30 doesn’t.
 
I did not take my time to read all what's written above, so could you please tell in short what type of head you need:
3.0 or 2.8
Carb or injection?
I might have one 3.0IMG20241029174319.jpgIMG20241029174134.jpg
 
I’m most probably going to pick up a head from a e28 528i tomorrow. Hopefully it’s in good condition.
 
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