Pulled the head today to have it rebuilt and possibly a little porting. I noticed a little chip/crack in one of the exhust valves and a little indintation in one of the pistons. Tell me what you think. The oil was also very milky???












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something went through your motor. i suspect mine will look the same somewhere. it's also the only valve without carbon deposits....is it stuck? looks like your were getting hot in that cylinder.

 

Looks like he cleaned it along with the top of the piston. Looks like you're doing a rebuild along with the refreshed head.

 

That would be a cracked exhaust valve. Probably destroyed the seat too. Head will need some work. And the corresponding cylinder's combustion chamber and piston are very "clean" from water leaking into it. You likely had a blown headgasket, causing water to leak into the cylinder and oil into the water, water into the oil, etc. Rebuild time for you.

 

the presence of oil on the block/head surfaces and the piston being so clean says head gasket blew...probably running hot...

turn your cam...does the valves move?

 

Hard to tell but you may also have a hairline crack on your head.

 

uh oh...

 

Yes it does. Just as easily as the adjoining valve.



No crack, thank god!




So, you guys dont think that I would be ok with just having the head refreshed?
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wow--ugly valve fo sho. the head gasket is blown, but you were planning on replacing it anyway, amirite? get the mls one from fm with arp head studs.

did you do a leakdown before the teardown to check ring health?

how much money are you willing to put into this project? that will dictate your course of action.

 

Why the mls one? I searched around here and plenty of people say the stock gasket and bolts are just fine. I dont ever have plans for huge power. 200-220 and i'll be happy for a good while.

Id like to spend as little as possible.

No I didnt do a leakdown. I was going to do a compression test but I knew I had a leak somewhere so I figured the readings wouldnt be right anyway.
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Multi-Layered Steel: http://flyinmiata.com/index.php?dept...04-20005++80MM

Though personally, I'm with "everyone" on this. I think the stock gasket is probably fine, and used one when I had my head off a few months ago. I did spring for the ARP bolts, simply because they weren't much more than stock and I prefer not to to re-use head studs.

With a hole that size in your exhaust valve, a leakdown test would have been worthless anyway.

 

FWIW I'd keep the stock gasket and head bolts. They are proven to hold up to lots of boost. Besides, the head gasket is like the fuse in an electrical system. It blows if something dangerous happens and is cheaper, easier, and faster to replace than the system it's protecting.

I hit the 99' with a 100 shot at 800 RPMs. The math shows that's over 600 ft*lbs of torque at that RPM. Could have bent rods, broke pistons, etc. But it just blew the **** out of the stock head gasket thank god.

You might could just do a head swap, assuming the deck is square and there is no cylinder wall scaring. Would have been nice to do a leakdown before pulling the head to have verified the condition of the bottom end.

 

Ok, when I replaced my blown headgasket the MAZDA gasket was a multi layer steel gasket, 3 layers. The Felpro one I replaced it with was also a 3 layer steel gasket. I don't see what's special about the FM one vs stock.

 

Especially at $98
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So, anyone else think I could get away with just rebuilding the head?
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Do you guys think cruising to lean could have caused this?
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Yeah. What AFR did you cruise at? It causes EGT's to climb and can burn a valve (imagine that). I cruise at 15.5 usually. I've done 16:1 a few times but I worry too much. I'd rather have the peace of mind that I'm not on the verge of running too lean. FWIW make sure the machinist that rebuilds that head KNOWS this is going on a turbo motor. They should cut the exhaust seat a little wider to help pull heat out of the exhaust valves to help prevent what happened to you.

 

eek. I have done lots of cruising at high 16's low 17's. I guess its time to richen it up and forget about mpg's. Do you think it also killed the HG?
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Damn. Yeah that's way too lean. I don't think running lean could blow a head gasket. Knock will do it in short order though. Perhaps knock occurred in boost with the burnt valve. That's my best guess.

 

so with 195k on the odo I guess the question is, WWYD? This goes out to everyone.
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