Detonation damage or another cause?

[ruthless]

Oops spelled the subject line wrong. isn't that just great! LOL

I am looking for some input from people experienced in this area, the shop has there ideas but I wanted to see what you guys thought. Long story short, had my turbo cobra to a track rental in May and had a boost controller issue (spiked to 21psi or 93 pump gas, normal is 17ish psi) that I thought caused a lifted head since it blew the bottom rad hose off. All the spark plugs where fresh and looked good when I pulled them out but #7 was wet. No signs of detonation or abuse in the other cylinders and I am not sure if this would be detonation or not but I am waiting to hear if the surface of the head and block are still true except for the burnt area. I also didn't find any coolant in the oil and the pic will show why.

After tear down we found the following. (I was informed that its in a strange area for a lifted head.)



All of the other cylinders look mint with no heat in the pistons.



Also pulled the cap from the cylinder with the issue.



The ideas I have heard so far are that one of the coil packs might have went bad or weak and the added boost caused the fuel not to burn properly in the one cylinder. (I would think that would be detonation??)

Post up your thoughts. I am just stumped because this doesn't look like damage I have seen in these engines before. I will post more if other damage is found.

Car ran perfect prior to this. I even have a AEM Fail safe wideband on the car that didn't trip to cut boost.

 

[03cobra#694]

Fixed the title for you.

 

[MalcolmV8]

What made you tear down the motor beside the lower radiator hose coming off and a wet plug? Did you compression and leak down test first? It sounds like the engine was running perfect prior to tear down or an I not reading that right?

I'm sure detonation shows itself in many ways but the most common and familiar I've seen is on the sides of the pistons. They look scuffed right towards the top on the sides. Spark plugs usually have signs on them too like metallic speckles on the porcelain and even on the grounding strap. A plug gap that gets closed almost like the piston hit the plug can be another sign.

 

[ruthless]

The #7 cylinder being full of coolant was why I pulled the engine apart. On disassembly we found that torched area on the head and gasket in the first pick. It needs welded and resurfaced to fix it so it isn't a simple swap in a new gasket fix.


That was my thinking on detonation and why my issue strikes me as odd.

 

[MalcolmV8]

The #7 cylinder being full of coolant was why I pulled the engine apart. On disassembly we found that torched area on the head and gasket in the first pick. It needs welded and resurfaced to fix it so it isn't a simple swap in a new gasket fix.


That was my thinking on detonation and why my issue strikes me as odd.

Ahh that makes more sense on why you pulled it apart. It's strange how the engine will be affected on just one cylinder initially when you push the limits. Back in 09 when I hurt my motor doing back to back highway pulls #4 cylinder was scored from piston swelling to much and scuffing it. All other cylinders and pistons looked just fine. I'm sure they were not far behind had I kept pushing the car but yeah I too would have expected all 8 cylinders to be equally damaged but not the case it seems.

 

[ruthless]

That's what I mean. The engine looks perfect except for that scorched mark and it happened in a half pass. This is a factory engine that was never opened and this was pass 9 at a track rental so its not like something was dropped in the engine during work. The engine had the turbo on it for about 4 years and never had the slightest bit of an issue. I was running a ported 01 Cobra intake with a spacer if that even matters.

 

[MalcolmV8]

Fuel injector or something specific to one cylinder failed on you?

 

[Torrance]

I had a dirty injector and burned my head just like yours, same cylinder too!

 

[ruthless]

I had a dirty injector and burned my head just like yours, same cylinder too!

Thank you. It could have been a weaker/dirty injector in the set since I am running 60s and know the boost was over what it should have been. Is #7 naturally leaner when this happens because of its placement in the intake manifold? If the cylinder leaned out I was expecting to see more damage and not a hot spot in one very small area. it could have happened so fast that it didn't cause other damage from heat too. I will get the injectors tested. I marked them when they came out so I know what one was in #7. I am patting myself on the back for that smart thinking. lol

 

[MalcolmV8]

I marked them when they came out so I know what one was in #7. I am patting myself on the back for that smart thinking. lol

I'm the same way. I mark which cylinder every coil, injector, plug and so much more came out of and every other item so when troubleshooting and you want to know "well which bolt was here" I can tell you lol.

 

[SlowSVT]

Perhaps I'm missing something but it appears that the only damage that has occurred is the head gasket has failed. That chamber looks better than most, nothing melted, no pitting, no white scorched surfaces, the valves are as black as night. You had a runaway turbo momentarily overboosting the engine and the gasket gave up the ghost. I would run a surface gauge over the deck and head you may have a low spot there it torched both surfaces when the seal was breached. You may want to take a skim pass on both heads and cylinder banks if the surface finish has been altered. If everything else looks good I would button the engine back-up and get it back into service. I take it you didn't hydrolock the engine with the cylinder hear full of coolant using the starter?

 

[ruthless]

Perhaps I'm missing something but it appears that the only damage that has occurred is the head gasket has failed. That chamber looks better than most, nothing melted, no pitting, no white scorched surfaces, the valves are as black as night. You had a runaway turbo momentarily overboosting the engine and the gasket gave up the ghost. I would run a surface gauge over the deck and head you may have a low spot there it torched both surfaces when the seal was breached. You may want to take a skim pass on both heads and cylinder banks if the surface finish has been altered. If everything else looks good I would button the engine back-up and get it back into service. I take it you didn't hydrolock the engine with the cylinder hear full of coolant using the starter?

The head melted where the gasket is damaged. My question is how can so much damage happen in that little spot and everything else looks mint? Was it a gasket failure more then a lifted head? Every engine I have seen with any melted parts is a big mess with melted or broke pistons. That and I want to make sure nothing else may have failed to cause this issue besides the quick over boost. I would hate to get it back together just to have a bad injector or something cause another issue.

No the engine didn't hydro lock, it blew every bit of coolant out and under the car and I didn't try to restart because I knew what happened. Pulled the car our of the lane and up against the wall and shut it off.

 

[ruthless]

Ok maybe I had a bit of the stupids about this.
Lifted head = stretched bolts but cylinder reseals some what while not under boost. (Combustion gasses seep past under pressure)
Blow gasket = Completely open gasket with a hole in it. (Combustion gasses get a open path)

Are those the basic meanings?

 

[SlowSVT]

The head melted where the gasket is damaged. My question is how can so much damage happen in that little spot and everything else looks mint? Was it a gasket failure more then a lifted head? Every engine I have seen with any melted parts is a big mess with melted or broke pistons. That and I want to make sure nothing else may have failed to cause this issue besides the quick over boost. I would hate to get it back together just to have a bad injector or something cause another issue.

No the engine didn't hydro lock, it blew every bit of coolant out and under the car and I didn't try to restart because I knew what happened. Pulled the car our of the lane and up against the wall and shut it off.

Using the term "lifted head" is a glorified way of saying someone blew a head gasket and is equating their engine to a blown nitro top fuel dragster. Those not only lift heads but can blow them clear off the block. I don't think our heads move more that .001" probably more like something measure in microns.

You didn't say anything about the piston melting where the gasket went south. Can you post a close-up pic of that area of the piston. You detonated which sent the cylinder pressure thru the roof blowing out the gasket but I'm surprised the damage was limited to only one cylinder.

You blew the bottom rad hose off because your water jacket was suddenly seeing cylinder pressure. Something tells me you were at 6 grand when the light turned green, you side stepped the clutch, tires bite, revs suddenly take a dip while boost goes thru the roof from the sudden load and rpm drop but the icing on the cake was that overenthusiastic impeller with #7 being the first casualty. I would take a closer look as the other 7 piston/rod assemblies to make sure nothing got "tweaked". Lots of time there is more damage then there appears only to find out on final assembly :nonono:

 

[Weather Man]

Would definitely have the injectors cleaned and tested. 7 injectors 3% on top of standard and one 3% under can be trouble.

 

[MalcolmV8]

Using the term "lifted head" is a glorified way of saying someone blew a head gasket and is equating their engine to a blown nitro top fuel dragster. Those not only lift heads but can blow them clear off the block. I don't think our heads move more that .001" probably more like something measure in microns.

I used the term with my turbo honda because I was literally stretching out the head bolts, lifting the head, and blowing out the head gasket. You are right it's lifting thousands of an inch and not flying off into the stands (wouldn't that be spectacular on the interstate) like a top fuel car but non the less lifting it. Switched to head studs and doubled the boost and never "lifted a head" again.

 

[SlowSVT]

I used the term with my turbo honda because I was literally stretching out the head bolts, lifting the head, and blowing out the head gasket. You are right it's lifting thousands of an inch and not flying off into the stands (wouldn't that be spectacular on the interstate) like a top fuel car but non the less lifting it. Switched to head studs and doubled the boost and never "lifted a head" again.

I see that you mean. If I blow a head gasket in my lawn mower I'll describe the problem to the mechanic as a "lifted head". Everything moves but I won't call it a lifted head unless I see flames shooting out at the mating line between the head and the block. I bet people would pay for that to happen to their engine just for the war story value alone how cool it that? :coolman:

 

[ruthless]

You didn't say anything about the piston melting where the gasket went south. Can you post a close-up pic of that area of the piston. You detonated which sent the cylinder pressure thru the roof blowing out the gasket but I'm surprised the damage was limited to only one cylinder.

No other damage was found by the shop and they specialize in these engines. They said there was no heat build up that they can see. Even the spark plug looked like new beside being wet and they went in fresh for this track rental. Exactly and we are all a little shocked that damage was limited to one cylinder and just the small area where the gasket went and why I am on here asking for input because I am not believing what we found. Normally I see melted pistons or pieces that banged around mi the cylinder. Unless I got lucky and had god like reflexes that saved me from bigger damage. I know the A/F was still correct because my failsafe wideband didn't cut boost. I checked the logs. lol

You blew the bottom rad hose off because your water jacket was suddenly seeing cylinder pressure. Something tells me you were at 6 grand when the light turned green, you side stepped the clutch, tires bite, revs suddenly take a dip while boost goes thru the roof from the sudden load and rpm drop but the icing on the cake was that overenthusiastic impeller with #7 being the first casualty. I would take a closer look as the other 7 piston/rod assemblies to make sure nothing got "tweaked". Lots of time there is more damage then there appears only to find out on final assembly :nonono:

Close but this was on the 9th pass at a track rental. lol Only left at 4.5k on low boost. Track wasn't prep very well. Had the boost controller setup to ramp in to 17psi and it went to 21psi. Half track coolant hit the windshield (I am betting from the coolant cap since its under the hood vent, and in a blink of an eye it popped the bottom rad hose at the same time I let out of it.


I am working with the shop to get a few options for upgrades depending on price. Kinda hard to leave those stock pistons in there when its down this far.

 

[ruthless]

I see that you mean. If I blow a head gasket in my lawn mower I'll describe the problem to the mechanic as a "lifted head". Everything moves but I won't call it a lifted head unless I see flames shooting out at the mating line between the head and the block. I bet people would pay for that to happen to their engine just for the war story value alone how cool it that? :coolman:

Yep my stuff just goes poof and that it. I never get the big BOOMING fireball like we all see on youtube. LOL

 

[Torrance]

I had my head welded and we ended up taking 0.007" off of both heads to clean things up.

We have a great guy here (local) that does a really good job on injectors. PM me if you want his contact info.