Question about cylinder head combustion chamber with pics...

white7g · Jun 4, 2015

I was cleaning my 2g head today to start reassembling my build and noticed this on the outter edge of the combustion chamber in cylinders 1 and 4. The car it came off of was a completely stock 2g with 116k was wondering if it is just casting from the factory and is fine to run or if something needs to be done about it, or is it just junk. thank you

bastarddsm · Jun 4, 2015

Looks like shitty casting. It's fine. you can smooth it out with a dremel and a sanding drum if you want. Don't nick the seats though.

BogusSVO · Jun 5, 2015

More 4g heads have that in the combustion chamber than don't.

motomattx · Sep 23, 2017

Thats detonation damage, lots of these heads exhibit it but its nothing to junk the head over, it will be fine but you might smooth it if you wanted.

donniekak · Sep 23, 2017

motomattx said:
Thats detonation damage, lots of these heads exhibit it but its nothing to junk the head over, it will be fine but you might smooth it if you wanted.

You sure about that? I've bought new oem heads that have that casting issue in the same place.

motomattx · Sep 23, 2017

That there is detonation damage, I've seen heads installed without it and pulled later with it.

ThunderChild · Sep 24, 2017

I'm gonna disagree unless the head had it's valve pockets redrilled after detonation had occurred. Also, the linear aspect of the marks don't look consistent with detonation, as well as no evidence with the rest of the chamber that I can see. I say it's just casting flaw, probably from evaporating water or air pockets release partway through the process, or a mold flaw.

Either way, smooth it out, run it.

donniekak · Sep 24, 2017

Detonation usually shows up as pitting on the exhaust side quench pad.

motomattx · Sep 24, 2017

tametalon92 said:
I'm gonna disagree unless the head had it's valve pockets redrilled after detonation had occurred. Also, the linear aspect of the marks don't look consistent with detonation, as well as no evidence with the rest of the chamber that I can see. I say it's just casting flaw, probably from evaporating water or air pockets release partway through the process, or a mold flaw.

Either way, smooth it out, run it.

The detonation marks are down past where it was machined.

ThunderChild · Sep 25, 2017

motomattx said:
The detonation marks are down past where it was machined.

Agree to disagree. The valve pocket was machined when those striated marks were already there. Do they cause an irregular edge on the valve pocket ridge? Yes.
But there is no evidence around the valve pocket, ridges, or quench pads that shows detonation to my eye. Granted, the head is freshly surfaced, but I still see no detonation evidence and still vote for casting flaw.

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Question about cylinder head combustion chamber with pics...

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