Good Evening,
We're in the middle of doing a head-gasket replacement on my cousin's '91 535iM. It overheated and blew the gasket on the #6 cyl. The head is straight with no apparent warpage or cracks. Unfortunately due to an errant hammer whack the #3 cylinder head got a ding in the rim. (the head bolts were literally siezed in the head itself due to a build up of the nastiest gunk I've ever seen). From what I can tell, the ding is small enough that the the headgasket ring should more than cover it (see the trace of the old gasket). Do y'all think this would pose an issue either immediate (headgasket won't seal) or long-term (headgasket fails in 50k miles...) I've never been one to take the cheap or easy way out, but he's just out of college, money is really tight (why we're doing it) and time is a major factor (need it done by next week if at all possible). Here are some pics:
http://i52.photobucket.com/albums/g8/riseosiris/head1.jpg?t=1188947391
http://i52.photobucket.com/albums/g8/riseosiris/head2.jpg?t=1188947126
http://i52.photobucket.com/albums/g8/riseosiris/head3.jpg?t=1188947129

Thoughts?

I would carefully get that part sticking into the open area off and then you'll be fine. As long as the ring covers it with a little room to seal your good.

Worst case is have a machine shop weld it up and surface the head, but I think your alright.

Might want to get some bosch silbers in there. The m30 really likes the correct spark plugs.

Be sure and make SURE there is no warpage, at a glance, mine appeared to be just fine, but after looking at it with a straight edge, it was off by .017 and that was too far to be machined, mine had to be heated and pressed back into shape. If you have any other questions about doing the HG, shoot me a pm. And as far as that dent is concerned, I would say take it to a machine shop and have them fix it up, it shouldn't be too much money, and doing a HG is such a PITA, that personally, I wouldn't risk it.
Here is what .017 looks like in case anyone was wondering...

Might want to get some bosch silbers in there. The m30 really likes the correct spark plugs.
Yeah I noticed the 4 types...Do you know what the model number is for the bosch's?

Be sure and make SURE there is no warpage, at a glance, mine appeared to be just fine, but after looking at it with a straight edge, it was off by .017 and that was too far to be machined, mine had to be heated and pressed back into shape. If you have any other questions about doing the HG, shoot me a pm. And as far as that dent is concerned, I would say take it to a machine shop and have them fix it up, it shouldn't be too much money, and doing a HG is such a PITA, that personally, I wouldn't risk it. Here is what .017 looks like in case anyone was wondering...

Yeah I hear you on the "not risking it" bit. I did cover it pretty diligently with a straightedge and didn't find anything that looked suspicious. I think we're going to take it to an independent shop tomorrow to have them disassemble the head and replace the valve seals etc. I'll have them double check for warpage. Thanks for all the answers!

You should seriously consider having that dent welded up and machined out. That is, if the head is usable. Reason being, any divots like that create a very noticeable hot spot in the combustion chamber. Hot spots = detonation, and because that is literally AT the seal ring, you don't want heat there.

We've had worse damage (don't ask) to cylinder heads on turbo cars that we've had welded up and machined true, so don't worry it's repairable. I would advise you to NOT put that head back on the block as is though. Don't have a shop take the head down and put seals in it - you can do that. I did my 24v head on my computer desk in about 1 hr after having lapped the valves in by hand. You definitely want to have the head surfaced at the very least. Don't slap it back on - M30 heads are known to warp. 0.003 out is probably fine that it'll clamp down but you can't measure that with a typical flat edge. At the very least have the machine shop surface the head 20 - 50 RA so you have a good surface for sealing.


Here is a pic so you can see:

http://blowneuroz.com/mygallery/E34%20525i%20Motor%20Build/head6.jpg

Thats after blasting and cleaning, but before machining. All is true and mint.

http://blowneuroz.com/mygallery/E34%20525i%20Motor%20Build/headdone2.jpg

You can see the marks from the gasket that was there previously - that shows how little they take off during surfacing. This is about 40 RA. I would really suggest you do this.