Hello! I am currently in the process of replacing gaskets and seals on my M42. As i took the cylinder head of the engine i was shocked to see all of the exhaust valves being bent.
Amazingly the engine was running like normal, just had a rough idle.
Anyways, the valve on cyl. 4 was so bent that it has struck the top part of the cylinder wall on number 4.
My question is, if I get a refurbushed cylinder head, is the block still usable as it is, concidering the damage is only above the piston rings (no marks further down).
IMG_6015.jpgIMG_6022.jpg
If it has raised up any metal around the head gasket fire ring sealing area that would be a concern. Looks like a bit of something may have been traveling between that bolt hole and the damaged area. Be sure it is dead nuts flat there. Also if any raised edge of the damage in the bore you can feel I'd smooth it out as any small bit sticking into the chamber can become a hot spot and promote detonation.
Other than that it is of no consequence.
Piston head is concerning, looks like the valve pounded it good and cut that divot(s)
The top ring land is almost certainly crushed but even if not those edges are bad, see above about detonation. Put a piston on your shopping list too.
Last edited by ross1; 03-15-2019 at 06:16 PM.
If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue
I dunno. I see a big chunk out of the cylinder wall, right at the very top, where all the stresses will be. I don't know about prices in Norway, but here, I'd advise just buying a used motor
Chris Powell
Racer and Instructor since, well. decades, ok?
Master Auto Tech, owner of German Motors of Aberdeen
BMWCCA 274412
German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471
Thanks for the advise. Ill be taking out the pistons to see if they need replacing. Will also be honing, with new piston rings and have a refurbished head ready to go on. Hopefully it will be allright
The piston you've shown and any others that may look like that are junk, nothing else to see.
Let us know how it works out, good luck.
If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue
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