Anyone ever see a head do this?
 

Quick history: Bought this 2006 Mazdaspeed 6 from an auction recently. Previous owner was an old guy that only took it to Mazda for work (I saw the service records from day 1). It was down one cylinder. Drove it home about 20 miles from the auction. Found no compression in cylinder 4. Engine has 120k miles on it. Found out the dealership did a timing chain and VVT unit about 5000 miles ago.

I checked the timing again before I tore it down and it seemed like the exhaust cam was out of time by 1/8 of a turn (that's how much I had to turn it to get the tool to fall into the slot). Put it back together and it ran the same. Tore the head off today and found this:

http://i1092.photobucket.com/albums/...ps1ae9012d.jpg

http://i1092.photobucket.com/albums/...psdf2f33e4.jpg

You guys have any suggestions on why the valve blew out? The oil and deposits in the cylinder seem excessive. Any ideas where the oil might be coming from? Is that maybe normal, since it's been driven some miles with no compression in that cylinder?

The cylinder walls in #4 are clean and smooth, like the rest of them. The intake was clean on #4 as well.

Any help would be appreciated!!

How do the tops of the valves look? Are there a lot of deposits on the top? If so it could be that the deposits built up too much on the valve face and caused it to not seat properly. If the valve can't seat properly then it will burn very fast because %75 of the valves ability to transfer heat to the head occurs through the seat.

Yes that is also an abnormal amount of oil in the cylinder too but you should also be concerned about where those pieces of the valves may have gone. The oil consumption could be multiple things. It could be from the valves, the ring gap, or bearing clearances. It's best you do a thorough inspection of the engine's bottom end too.

that valve is toast.

whats the compression like for that cylinder, possible ringland failure? or worn rings

doh, probably cant get a good compression reading for that cylinder with that bad valve

pull that piston out and check the full bore and the rings/ringlands

replace valves, re-ring, head gasket, and fire it up :smile:

Some oil consumption/buildup created hotspots that eventually burned out the valve. The motor has a good number of miles and you don't know what fuel etc. was used in it.

There was zero compression in that cylinder. I got a fairly good deal on a rebuilt head, so I'll just sell this old one for parts.

I ran the piston down to the lowest spot in the rotation and the cylinder wall felt no different than the others. I'm going to cross my fingers that the build up in that cylinder was caused by driving it on 3 cylinders for a few hundred miles. I'm assuming #4 never "came up to temperature" and the rings probably weren't sealing well. That and fuel was being injected there with no ignition going on.

I'm going to have the injectors flow tested as well, to make sure #4 wasn't going lean and causing an overheat condition, burning the valves.

To answer Mazdazilla's question, the backs of the intake valves look terrible, with lots of caking/build up (110k worth, I'm sure). I haven't looked in the exhaust ports with a flashlight to see if the backs of the exhaust valves are visible.

Parts are on order and I hope to have most of them tomorrow. Might get a chance to work on reassembly this weekend, but it's probably going to be next.

Thanks for everyone's input! Hopefully I'll get the issues wiped out and the engine will be good for another 100k.