Did they really mill my block?

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VG30DETT_build
Posts: 2
Joined: Fri Jun 29, 2018 7:18 am
Car: Nissan 300ZX Twin Turbo JDM Automatic Performance Build
Nissan 300ZX Twin Turbo JDM Manual Standard

Did they really mill my block?

Postby VG30DETT_build » Fri Jun 29, 2018 8:47 am

Hi everyone. This is a question that is suited to those who build engines or otherwise have knowledge of machining of blocks and heads.

I have a 300ZX that I had an engine built for it and installed at a performance place. It blew a head gasket after about 2000 km (about 1300 miles).

So I have it in pieces in my shed and I'm looking at the head gaskets, MLS just like they're supposed to be. And I'm looking at my block, looks like I'd expect.

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So then I scrape it to get all the rust, viton and stuff off and I'm starting to see little polka dots. Then I start lapping to get the remaining stuff off and I can't. Those little polka dots, machining ripples, scratches and other corroded bits are not coming out and the surface appears to be far from flat. It's about this point I've realized there is no worming out of getting it milled *sigh*.

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They are at the right angle to the light in the bottom right corner of that last photo, that's what it looks like in the flesh.

So my question is - does anyone know if those little polka dots are there from when the stock head gaskets were on the engine? There doesn't appear to be anything like that on the MLS head gaskets I removed. I'm just beginning to think that the block may not have been properly prepped for MLS head gaskets in the first place. My understanding is that it's even milled differently to achieve a <50RA finish per Cometic requirements and big ripples from bad feed rate/wrong tool/blunt tool are unacceptable. Can anyone confirm or correct me on this?


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