ls7 head sealing issue

[user-23911]

Too lean as well as too much timing.

[Newold1]

Reusing the LS stock TTY head bolts is always risky and not a good candidate for trying to reassemble and torque a very expensive LS variant.

My thought is use the ARP head STUD kit and the reason is that studs have nice fine threads on the top and allow very incremental even torquing of the cylinder head and that can lead to less head bolt/torque issues. Definitely worth the nominal added expense over bolts. JMHO

Check the deck on the block and obviously the head deck surfaces and RA's to make sure you've got flat even surfaces to begin with.

Not sure you've got a timing issue but I know fuel changes can affect cylinder pressures and TTY bolts will yield more under high loads and that lifting can cause a head gasket leak. Sounds like you may have found that out.

[CGT]

I'm reasonably sure the OP didn't reuse the tty bolts.

Too lean as well as too much timing.

Are you seeing something in the photos that is indicative of this? Im curious.

You say you "recently" switched to E85. What was the previous fuel? It's not easy to detonate E85. Is it possible the damage started on the previous fuel?

This is an interesting point. Knowing that a lot of late model street guys end up bucking up for the E85 conversion ultimately for knock resistance on the cheap and convenient (I'm one of them) Maybe it was "hurt" in some way prior to the conversion?

I would also be interested to see if the connecting rod is damaged or bent.....not sure if titanium bends? Chicken or the egg scenario on the actual damage. Did the liner crack and start the process, or did the piston breaking take out the liner??? Could it have lifted the head under throttle enough to fill that cylinder with coolant and detonate or hydraulic???? MOO

[slo-svt]

You say you "recently" switched to E85. What was the previous fuel? It's not easy to detonate E85. Is it possible the damage started on the previous fuel?

Anything is possible i suppose. I have never noticed any smoke while driving before though. I raced twice and then when i went to race again someone driving behind me said they noticed it smoking the whole time. When I did a burnout is when it let go and really started really smoking.

I rotated it to tdc on that cylinder and the piston is still potruding out of the bore so I dont think the rod is bent. I also noticed that piston number 5 is cracked int he same spot but not broken yet. Still kind of unsure about the order of events like CGT was saying. I tuned about a half point richer than its ever been and the timing was pretty conservative I think. I have had as much as 30 degrees in it without any knock sensor activity and it was had 28 in it at the time of failure. Need to get the engine out. I also did NOT reuse the tty fasteners. New fasterners were installed at the time of head installation. I don't see any signs of valve contact on any of the pistons.

[slo-svt]

piston 1.JPG

[slo-svt]

piston (2).JPG

[CGT]

Rings butt?

[user-23911]

No, that's normal damage after detonation.
Seen it lots and lots and lots of times with E85 N/A conversions as well as turbos on pump fuel.

E85 pre ignites when it's too lean and WB gauges never seem to read correctly when you want to depend on them.
Knock sensors pick up knock but not pre ignition.
Pre ignition will come first followed by knock as the piston gets hotter.

E85.........it's usually reported that you need 30% more fuel but when you work it out, you need closer to 50% more, that's by volume.

Well if it's got 30% less calorific value, you don't need 30% more do you?
You need more like 50% more.


The ratio of 9.8 to 14.7 is 0.6666
And
The ratio of 14.7 to 9.8 is 1.5.

So you need 1.5 times as much by weight.
Injectors don't flow the same volume when comparing E85 to petrol.....most people don't know that. With E85 and injectors the flow will be maybe 10% less by volume........how would you know?
BUT
The SG of E85 and petrol isn't the same either so the numbers tend to cancel mostly.

[user-23911]

With the stoich ratio of ethanol being 9.8 and allowing for E85 being 85% ethanol and 15% petrol, you don't need 50% more by weight ........you need .85 x .5 more which is 42% more.

Certainly a lot more than the commonly quoted number of 30%.


Unless the 15% is made from something else like toluene in which case it's a lot denser so you need a lot less of it.


Then there's the E85 content sensors........they can read wrong too.
They get messed up by any water content.
There's a couple of good videos on youtube on that by Dave Buscher.

https://www.youtube.com/watch?v=8DZhLjwsWVY


When it comes to electronics and cars........nothing actually works in the way in which you're told it does.

[32vape]

What I've found on the higher compression LS engines running e85 is they require a lot less timing. 30 degrees with 13+:1 and e85 is way too much. The knock sensors will not pick it up either with e85. It just hammers the bottom end with the peak pressure happening while the piston is trying to compress the expansion. It will be interesting to see what the bearings look like. That's usually what goes first. 22 degrees at peak torque and 25 at peak power is probably all it needs.

[slo-svt]

No, that's normal damage after detonation.
Seen it lots and lots and lots of times with E85 N/A conversions as well as turbos on pump fuel.

E85 pre ignites when it's too lean and WB gauges never seem to read correctly when you want to depend on them.
Knock sensors pick up knock but not pre ignition.

I tend to trust my wideband. It afx with the ntk sensor. the sensor is almost new and is calibrated for about 10 min before it goes in. I was tuned to .85 lambda and dips down to .82 from 5000-6000. We can talk about details on e85 all day and how much more it requires but at the end of the day the car had more than enough pump and injectors for what im doing. IDC @ 7000 after fueling was done was only 60%. I wold be more inclined to belive that ignition timing is the culprit than fueling. The injectors (although they are new) will be flow tested before they are installed on the new engine. It would be interesting ot take a fuel sample and see what it comes up with. I tested it with the gm composition tester 2 days prior to filling up that day and it was 85 percent. I however, never let it sit to see if anything seperated out of it.

What I've found on the higher compression LS engines running e85 is they require a lot less timing. 30 degrees with 13+:1 and e85 is way too much. The knock sensors will not pick it up either with e85. It just hammers the bottom end with the peak pressure happening while the piston is trying to compress the expansion. It will be interesting to see what the bearings look like. That's usually what goes first. 22 degrees at peak torque and 25 at peak power is probably all it needs.

Definatley interested to see what the bearings look like. Surley if it was detonating bad enought to break something it wouldn't have ran as good as it did. I beat a car that has alledgedly been 135mph (i tend to belive it did based on other cars i have seen it race) pretty bad when this happened.

[CGT]

Whats more accurate? Checking ethanol content by specific gravity(I assume that's how the sensor operates) or manually with a hydrometer? I have compared GM's Fuel Composition tester J44175 to a reading from a hydrometer and it was very very close.

Are timing requirements really that different for Ethanol vs Methanol? I can't see the OP's engine having too much timing at 30°. A 427 inch motor with a (in my opinion) shitty chamber with virtually no quench area.

SVT? Looks like your not going to know more until the engine comes apart. Some of things mentioned in this thread make a little apprehensive about my own E85 burning late model vehicle. SVT name driving LS powered stuff, are you confused?

[slo-svt]

SVT? Looks like your not going to know more until the engine comes apart. Some of things mentioned in this thread make a little apprehensive about my own E85 burning late model vehicle. SVT name driving LS powered stuff, are you confused?

I agree. The engine needs to come out and apart. I'm not confused I also have an single turbo 2003 Cobra. It runs on the tears of 5th gen camaro owners so I haven't driven it lately due to the scarce population of them in my area.

[Newold1]

Just some observation from the pics. The pics show a deck that does not appear to have been even slightly decked for straightness and low spots?
The pics show you are using the stock factory Hyper-eutectic pistons. Not great choices for the upgrade performance levels you are working with. Check and deck that block and go back in with a better set of forged pistons and rings with correct clearances and use a good set of Cometics X gaskets and ARP studs. As for tune sounds like you have a good understanding there and the tune experts can help you get that right.

[GARY C]

Could the damage have had started prior to the E85, what fuel did you run before?