Head gasket likely? And more...

[5150DSM]

A sad day in the DSM world, at least my DSM world. Been pushing the car lately, incrementally upping the boost and tuning for the new levels. I had planned to do water/meth soon and was trying to max out my set-up beforehand, see how far I could take it on pump.

Yesterday I had 18psi, with 0 knock and 30* of total timing at 6500, car was feeling great, injectors were only at 71% DC so I figured I had a little room. This morning, upped it to 20psi and started my tuning runs. (on the way to work )

Second pull at 20psi, right at 6156, I hear a loud PFUUUUT, and the car lost all power, sounded and felt like a I/C coupler blowing off.(Ask me how I know) Pull to the side of the road, car shuts off and won't restart. Sounds like there is no compression, motor spins and spins but doesn't even try to start. So, I have it towed to my shop.

At lunch I went out and was able to spin the motor freely by hand, cams and crank roll together, no binding, no stopping, etc... When I get to TDC I notice that the exhaust cam is 1 1/2 teeth off. Ok, so I jumped time a little, my old ass hydraulic tensioner probably gave up the ghost. Whatever, been here before.

My question is... Would you think that I would hear the head gasket blow? And, do you think that is what I heard. Additionally, when I popped the hood I found that a large bolus of oil had spewed from the dipstick and coolant from the reservoir had spewed as well. Is this indicative of the HG or bent valves or both? Any and all replies are welcome.
Thanks

There goes my baby.

 

[92AWDHX40]

Do a leak down, compression test to see whats going on, first.

 

[5150DSM]

Forgot one thing... I was the dumbass here. I neglected to upgrade to ARP's for the head before I started pounding boost through the E316G. Personally, that's why I think it failed.

 

[Turbotsiawd]

No arp's should have been the first thing you bought.

You probably had some head lift which took your gasket with it.

 

[Anubis_4_99]

Set your timing, and do a compression and leak down test as suggested before you assume the gasket is gone. Those are free, ripping into it right away cost's money that may not be needed.

 

[5150DSM]

Thanks for the replies. I do know to do a compression and leak-down test after I re-set the timing. I guess I didn't phrase my questions very well.
I meant to ask whether you guys thought I was on the right track as far as the damage and whether there were other things you thought I should be looking for. See, I'm gathering parts that I think I'm going to need this weekend; I work for a shop and can get jobber prices during our business hours. (not on weekends) So, I want to gather as much as I can at low prices before I run into something and have to pay retail.
Thanks again.

 

[5150DSM]

Ended up being more.

Lost the bottom end as well as the head gasket. Timing was fine. To me, it appears that when the HG blew, it dumped a bunch of coolant into the cylinders. Of course coolant cannot be compressed so the weakest link failed, in this case my poor pistons. I haven't completed the tear-down yet but judging by what I can see it looks like the the tops of the pistons deformed under pressure and it just cascaded into the lands and skirts. Take a look, tell me what you think. BTW, before I pulled the head compression was 145-0-0-0. Any input is sincerely appreciated as this has become a forensic examination at this point. Find out what fu(ked up and prevent it from happeninig again.

 

[Sebba]

Wow that's some serious energy.

 

[5150DSM]

0 Fu(king knock. But went boom anyway. Time to pull a 6million dollar man on it.

 

[Anubis_4_99]

Wow. Dont know what else to say, .

 

[Sebba]

The pistons definitely don't look like they were taking knock.

 

[Calan]

Yesterday I had 18psi, with 0 knock and 30* of total timing at 6500, car was feeling great, injectors were only at 71% DC so I figured I had a little room. This morning, upped it to 20psi and started my tuning runs

Was that at WOT? What kind of fuel?

 

[5150DSM]

Was that at WOT? What kind of fuel?

Yes, at WOT. A lot of timing, I know. Maybe from the adjustments on the MAFT. 02's were at .88v so I felt fairly safe. Planned on a wideband next weekend when I did the 3" cat. Oh, this was on pump gas... 91 Cali octane.

 

[Calan]

$10 says your knock sensor wasn't working. 30* of timing is ridiculous, even for race gas. But on 91 .

I just don't see it happening.

 

[5150DSM]

$10 says your knock sensor wasn't working. 30* of timing is ridiculous, even for race gas. But on 91 .

I just don't see it happening.

KS is brand new(mitsu)... Meaningless as far as it goes but it's all the info I have to work with. I know 30* is a shit ton but that's what it was. I certainly wouldn't choose to run that much advance. Base timing was at 5 btdc, no physical advance on the cams. I understand that narrowband values are not ideal to tune with but I have found in the past that .85-.90v usually works out around 12.5:1.

Do those pistons appear to have taking a detonation beating to you?

 

[Calan]

Do those pistons appear to have taking a detonation beating to you?

To be honest, I'm still trying to get my head around exactly what it looks like. My best guess is that they plasticized and deformed due to extreme heat in the cylinders.

If you were truly running 30* advance and upwards of 12.0:1 on 91 octane gas, that should do it...assuming that the thing wasn't knocking like crazy beforehand. Since you weren't running a huge amount of boost, I guess it's possible that you could have have just cooked the pistons with heat and no pre-detonation.

Regardless, running that lean and with that much timing on 91 pump piss is just asking for trouble.

 

[5150DSM]

To be honest, I'm still trying to get my head around exactly what it looks like. My best guess is that they plasticized and deformed due to extreme heat in the cylinders. And if you were truly running 30* advance and upwards of 12.0:1 on 91 octane gas, that should do it...assuming that the thing wasn't knocking like crazy beforehand.

So that doesn't look like pressure deformation to you. Meaning that the coolant flooding the cylinders and being incompressible just broke the weakest link in the chain.

I ask, because I cant find any evidence of detonation. Nothing that would lead me to believe it was bad enough to smoke the pistons anyway. Plugs showed a nice even tan color (except for theoil and coolant), no white spots, no burns. I don't see any scorching on the pistons or in the combustion chambers, valves are not burnt, etc, etc...

As far as AFR, that's just a generic extrapolation. I'm wasn't running a wideband at the time so I could have been 16:1 for all I know. I had .88v from the narrowband which has been plenty safe for me in the past. That being said, most of my previous tuning on the 4g63 has been on 93 octane pump so...

 

[5150DSM]

I didn't want 30*. My DSM did that part on it's own. I wonder if running a manual ECU in an auto car had anything to do with it?

What I really want to know is if my bores with only 15k on the previous hone job are still round and usable at standard diameter?

 

[Calan]

So that doesn't look like pressure deformation to you. Meaning that the coolant flooding the cylinders and being incompressible just broke the weakest link in the chain.

I have no actual experience with that, but I don't think so. I would expect the pistons to show cracks or breakage if that was the case. In those pics, it looks more like they became elastic and deformed, unless they are actually sheared off and my eyes are just messing with me. .

Do the ring lands show any clean breaks?

 

[5150DSM]

Do the ring lands show any clean breaks?

I don't have the pistons out yet but #2(first pic) definately shows the top land broken, #3 (second pic) also appears to have top land damage. #1 piston(not pictured) looks perfect from the top, no deformation, no breakage, nada. Make of that what you will.

 

[5150DSM]

Appreciate your time Calan. I'll finish the tear-down tomorrow and report back with the findings. In the mean time, any thoughts on the bores? I don't have a dial bore gauge and wasn't planning on pulling the motor for rebuild. Kinda flying by the seat of my pants here.

 

[WES_393]

My best guess is that they plasticized and deformed due to extreme heat in the cylinders.

That's what it looks like to me. Extremely hot gasses slipping past the rings which gave the pistons a good burn. Then, over time, the hot gasses continued to take this route until the ring lands were toast. Once the rings couldn't hold a seal, the engine went pop. It seems to me though that you would have noticed a huge amount of blow by beforehand, but the dipstick popping out confirms that near the end there was a lot of pressure in there. So I think that's a pretty appropriate theory.

In every case of hyrdo lock I have seen, the rod is bent but the piston is still in decent shape. Typically rods are the weakest link in a bottom end since they are the "levers" of the engine and aren't immediaetly supported by anything. It looks to me that the culprit is high cylinder temps over an extended period of time. Either from the very high timing, lean running condition, or a combination of both. Not sure why you were cranking up the boost without a wideband though.

The bore will at the very least need a new hone. But with damaged rings and ring lands, you probably have some pretty good scores in the cylinder. You've got it apart this far, why not just pull the engine and get it bored .20 over? Or buy a used shortblock and throw it in. Either way that block will need to come out.

 

[5150DSM]

Thanks WES_393. It was my daily and I don't have another so I was trying to get it back quick. But you're right.

 

[5150DSM]

Update.

The Block is trash. I found a huge chunk taken out of the #3 cylider wall. 1/4" wide, 3/4" long and about 1/16" or so deep. Good thing I have another block. It's an N/T block but aside from the lack of oil squirters it should suit my needs. Going to the machine shop tomorrow to have cleaned and inspected. Wish me luck.
Thanks for all the replies and help. I'll post back after the inspection.

 

[5150DSM]

Took a while to get back to this. I had to order everything to rebuild this thing.

Anyway, damage got worse and worse as I dug deeper. Here's some pics for your amusement. After this post I'll move this over to a build thread because that's what it's become. Enjoy.