motors got a drinking problem

[SLP IROC-Z]

Cars been running rough cold lately. Thought it might be plugs since they have over 20k hard miles. After checking the misfire pids starting it cold cyl 4 got 73 misfire counts right off the bat. I pulled the plug and did a compression test I got 200psi at first then 190. After had the compression tester off some coolant dripped out of it. I wasn't sure if it was residule from something else we worked on or from my engine. The car was down a bit on coolant. I filled it uo and put a new plug in and it seemd to run better. Well this am it wouldnt even turn over. Pulled #4 plug and cranked the coolan out. Drove it to my shop, getting ready to pull the topend first compressin and leakdown test all the cylinders. I guess cracked head or bad headgasket. If its the headgasket that concerns me. Ive never had to deal with much knock retard with this thing. I run 22-23* of timing at WOT, I can run 26 but it doesnt go any faster, doesnt knock either. Its never got hot. Never touched the rest of the timing table (stock z06 table).

Heres the plug from that cylinder.

[Z28]

So if its a cracked head whats the plan?

[smokinss]

Sucks man. If its not one thing its another. My valvesprings are finally worn out so that's getting done in a week or so. Never ends.

[SLP IROC-Z]

So this is the culprit. Cant tell if its a crack or what but it wasnt there when i assembled it. The heads were cut pretty rough and it looks like part of the grain in the metal blew right out. this is right where the fire ring of the headgasket is leading to a water jacket.

[ZFreie]

Sucks to hear Joe, post pics if you get a chance.

[Formula413]

Crack in the head? Do you have another set of heads kicking around you could run?

[84ta406]

Any chance you can grind it and TIG it? Resurface the head and call it kosher?

[SLP IROC-Z]

Editied, picture didnt show up for some reason. it can probably be fixed. already been cut .020. half of the valves arent sealing either.

[84ta406]

How bad are the seats/valves? Lap them in or use a stone by hand?

The old adage is true, things run best right before they break.

[Slowhawk]

I've never seen heads surfaced like that before.Those are deep cuts,kinda looks like someone ran down them with a belt sander.

[smokinss]

Kinda what I was thinking Don!

[SLP IROC-Z]

yeah they are very roughly cut which is what i believe lead to this happening.

[Slowhawk]

It's not just the rough cut, it's the straight across the heads too.
That crack I doubt is from the head surfacing. It's probably a casting defect. I've seen stuff like that from Patriot before but not GM run stuff.

[KLAB]

Joe who did the milling again? LC?

[SLP IROC-Z]

Turns out head wasn't cracked. Also all the valves were leaking, can't believe it ran so good. Heads were also cut no where near as much as I had asked, so the compression wasn't much over stock.

[KLAB]

failure