PS this is why I replaced the head... :o)

[Ferret]

http://static.flickr.com/81/267970783_1ce984a7e4_o.jpg

Identical cracks on 4 & 5

[DaveVoorhis]

That'll polish out.

[Ferret]

That'll polish out.

haha

[632 Regal]

is this from over heating?

[Ferret]

I think so - the thermostat blew and it overheated a couple of months before it blew.

This head has a seriously crap design - it's been pushed too far - only having such a small amount of metal beween the edge of the bore and a water port is shocking. No wonder this particular engine has a reputation for going bang.

They fixed it somehow on the vanos engines though.

[Dave M]

Out of interest, What cylinder is that? I have a theory about #5..........

Thanks for the cool pic ;)

Dave M

[Ferret]

I think #5 was the one that was ejecting oil and water when turning it over with the spark plug out - either that or it was 4. Amazing water pistol.

That crack runs all the way up into the cam area.

I've got some more detailed photos of the rebuild process if I can find them. (I've just rebuilt my pc and everythings archived.)
Oh, this is what it's doing to the plugs in #3

http://static.flickr.com/83/267960482_822545ac61_o.jpg

[SnakeyesTx]

It's making Chicken curry?!

Side note : Boo on +4 plugs. I've got some horror stories about their aweful design and their even more aweful labor claim rulings.

[guinness]

I think #5 was the one that was ejecting oil and water when turning it over with the spark plug out - either that or it was 4. Amazing water pistol.

That crack runs all the way up into the cam area.

I've got some more detailed photos of the rebuild process if I can find them. (I've just rebuilt my pc and everythings archived.)
Oh, this is what it's doing to the plugs in #3

http://static.flickr.com/83/267960482_822545ac61_o.jpg
Thanks,,, now I'm getting hungry

[winfred]

no they didn't, the vanos head and non vanos head crack on #4 or 5 in that exact spot with equal vigor, and on rare occasion they crack between the exhaust valves (had one that was cracked between every exhaust valve on every cylinder), i don't really see any real differences between m50 m50tu and m52 heads that they couldn't be interchanged and just use the correct cams to make it vanos or non vanos, i've done so many m50/52 heads i couldn't wager a guess closer then a few dozen


They fixed it somehow on the vanos engines though.

[winfred]

+4 super's ? those aren't platinums unless they finally started putting a real center electrode on them



http://static.flickr.com/83/267960482_822545ac61_o.jpg

[genphreak]

Everyone and their dog is getting them now (super +4s)... I hope they didn't come in a Platinum packet like mine did (I got ripped!)

I don't think the heads are weak or too finely milled near the valves. They are big valve motors so that's the way they have to be (we like them like this, it is what makes them so fun!). The motors are just finely balanced given that they are made from alloy and steel and are very long by design.

I am not surprised that overheating once they have got to this age can cause problems, 9 times out of 10 this is due to extended neglect (coolant and the various system components)...

[Ferret]

I don't think the heads are weak or too finely milled near the valves. They are big valve motors so that's the way they have to be (we like them like this, it is what makes them so fun!).

Yeah, I was trying to point out though that if that coolant port had just been 1cm further away (like it is in the 2.0 head) that crack would probably never have happened...

Oh, and whoever said they're prone to cracking between the valves as well - yeah one of them had done it.