What cause these damage?

[tryingbe]

No foreign object, timing was correct, wiseco pistons, etc...

Piston one. Blue stuff are the paper towel.
http://thelostartof.net/omnidead_7185.JPG
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http://thelostartof.net/omnidead_7183.JPG

head cylinder number one
http://thelostartof.net/omnidead_7178.JPG
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http://thelostartof.net/omnidead_7177.JPG
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http://thelostartof.net/omnidead_7176.JPG
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http://thelostartof.net/omnidead_7175.JPG

head cylinder number two
http://thelostartof.net/omnidead_7179.JPG

head cylinder number three
http://thelostartof.net/omnidead_7180.JPG

head cylinder number four
http://thelostartof.net/omnidead_7181.JPG

[88_pacifica]

Did this motor run hot for extended periods or ever have detonation issues? Being that it's an aluminum head with that kind of pitting and fragmentation, I'd think that there was either a point where it ran outside of it's heat range or it simply is a case of getting a poor casting. I have seen this before on aluminum GM V8 heads, but typically the compression was set very high and the octane was well over 110+... Was this a DD?

[cordes]

I too would say that it got hot from some thing. Some detonation perhaps. I have not seen a head that melted due to det. I think Simon had that happen to him recently, perhaps he would know.

[turbovanman²]

Lean baby lean. The oil isn't helping either. Some of the marks are probably due to a previous repair and thats the way they look.

[22mopar]

100% detonation. excessive oil leakage increases compression ratio and increases detonation, plus running really lean just like simon says. you have a problem to fix.

[Frank]

My understanding about the oil is not he compression, but the fact is that half the time it is still burning a little when new fuel & air enters the chamber.


Frank

[88_pacifica]

Did this motor run hot for extended periods or ever have detonation issues? Being that it's an aluminum head with that kind of pitting and fragmentation, I'd think that there was either a point where it ran outside of it's heat range or it simply is a case of getting a poor casting. I have seen this before on aluminum GM V8 heads, but typically the compression was set very high and the octane was well over 110+... Was this a DD?


I too would say that it got hot from some thing. Some detonation perhaps. I have not seen a head that melted due to det. I think Simon had that happen to him recently, perhaps he would know.


100% detonation. excessive oil leakage increases compression ratio and increases detonation, plus running really lean just like simon says. you have a problem to fix.

Woo-hoo... do I get a cookie. I'll take the one Simon didn't get for solving Allmotors last quiz! :D

[tryingbe]

How do I go about to determine what in fuel/electronic failed?

Custom Cal, +40 injectors, 255 pump. Never went above 12psi.

BTW, oil was added to the combustion chamber after the engine overheats and had coolant entered the chamger a week ago to prevent rust.

[mo' parts]

definitley looks to be detonation. i had one pitted worse than that a while back.too much timing/boost, not enough fuel/octane.
more info on set-up?

[tryingbe]

CA 91 octane gas, no more than 12psi, 3 bar cal, 3 bar map, +40 injectors, stock regulator, 255 pump, 2.5L with forged wiseco, G-head, TII turbo, FMIC, stock exhaust manifold, 12 degree timing which what the cal is called for, 185 degree thermostat, BPR6ES plugs...etc

What else do you want to know?

[mo' parts]

have an egt? a/f? if so what kind of readings?

it looks like a bit of carbon build up on the valves, could the plugs be a hair too cold? cal. a little rich? carbon could have caused some hot spots leading to pre-ignition...(also looks like some of the build-up has chipped off) just a though.

[88_pacifica]

Well, I'm a GN man myself, but since the stock GN's had iron heads this one is a bit of a toughie for me. If I had to make a guess by looking at your setup the only two areas that might be questionable would be the stock reg or the maybe the cal. Everything else seems to be spot on fromwhat i've learned thus far. How long did it run till this happened? If it had quite a few miles and you never had HG problems, you could eliminate damn near everythignelse outside of general parts failure. I know a buddy of mine that had an LT1 with a supercharger had this happen almost to a T, which is how I knew that detonation might be an issue, when his injectors' filters clogged up some and got sless flow which caused a lean condition. This was from bad gas though as he was notorious for buying the "cheap stuff." If the regulator were not able to provide the pressure and the injectors were clogged, I could see this happening slowly over time as the buildup on the pistons and head would suggest. However, this is purely speculation. I am no TD guru by any stretch, but a simple test at the injector itself or even a quick check of the filters in the injectors might be warranted... just my .02... Good luck Harry. :(

[zin]

CA 91 octane gas, no more than 12psi, 3 bar cal, 3 bar map, +40 injectors, stock regulator, 255 pump, 2.5L with forged wiseco, G-head, TII turbo, FMIC, stock exhaust manifold, 12 degree timing which what the cal is called for, 185 degree thermostat, BPR6ES plugs...etc

What else do you want to know?

I may be just showing my inexperience with these engines, but it seems weird that there would be signs of detonation in the quench area and on the side opposite of the spark plug. I would expect that point to be one of the cooler places in the chamber, although that is where the end gases would reside...

[turbovanman²]

Whose custom cal?

[BIGBRUDDA]

It actually resembles Electrolisys pitting.And it's adjacent to the metallic ring on the head gasket.
Was this head ever off or engine stored long term before? The water passages seem kinda rusty too.
Detonation pitting usually occurs close to or directly under the ignition point. And is more likely to pull metal off the piston.
Measure the head carefully.If it has been surfaced or ground previously,that could lead to the nicks in the piston.By way of diminished valve-to-piston clearance.

[tryingbe]

have an egt? a/f?

No gauge other than boost, I had plan to install them once I up the boost. I didn't think I need it just yet as I was basically running same boost as a stock 2.5L.


Whose custom cal?

TU.


Was this head ever off or engine stored long term before? The water passages seem kinda rusty too.

I was told it was a new casting from 84, slightly ported and smooth out intake/exhaust ports. Here's what it looks like when I got it.

http://www.hardcars.com/thepriestmike/omni/newhead_3597.JPG
http://www.hardcars.com/thepriestmike/omni/newhead_3598.JPG
http://www.hardcars.com/thepriestmike/omni/newhead_3599.JPG
http://www.hardcars.com/thepriestmike/omni/newhead_3600.JPG
http://www.hardcars.com/thepriestmike/omni/newhead_3601.JPG
http://www.hardcars.com/thepriestmike/omni/newhead_3602JPG

[Turbodave]

Interesting to see a bathtub head that's been crossdrilled like that.

In the first picture or two at the top (the "after" ones), it looks to me like maybe that exhaust valve is open more than normal. It could just be the camera angle, but was the valve hitting the piston? I don't think detonation could cause that.

[tryingbe]

No contact between valve and piston.

Car was running when I pulled it apart. Exhaust gas was in coolant and coolant was in the chamber. Oil was clean though.

The clear oil you see on the cylinder head is the oil I pour in the cylinders after discovering the issue, I was trying to prevent rust in the cylinders.

[88_pacifica]

Harry, how many miles are on this thing? Just out of curiosity....

[tryingbe]

Since I put on the rebuilt turbo?

Less than 2000 miles. Drive it for 2months going home and work (12 miles each way), most of the miles are put on going from Mesa, AZ to Norwalk, CA then Modesto, CA, then back to rest stop 86 on 10 freeway, AZ. (where it died)

[88_pacifica]

Man, I'm tellin' ya... I swear it looks like the exhaust side of the head got too hot and "bubbled" the edges of the chamber where it meets the block. If it we're a really bad casting though, I would expect that everywhere. Since you said it was a NOS casting I would question if it was truly OEM. I know the heating and cooling cycle is especially hard on heads that are aluminum that bolt to iron blocks, but this is extremely unusual in that it is only on the back side of the head. This may sound stupid, but what cam are you running? Is it a longer duration one? You said it's set @ 12* though so it seems odd unless it is an aftermarket maybe. I would think that if the duration were off then the egt's would rise. I'm not sure without you having that gauge though and you really can't tell by the coolant sensor. If for some reason, outside of being lean of course, the valve cycle duration was longer than usual or at different times then yes, I could see it melting the sopts in the aluminum, which would give flecking possibly in other areas of the head and exhaust. Does this make sense? I'd have to think it was definitely temp related though before anything else...

edit: This was initially one of the reasons GM originally didn't use aluminum heads on the GN supposedly, but I think it was actually a budget thing.

[tryingbe]

The calibration calls for 12 degree timing.

It's a roller cam, that's all I can tell you. Took it off a junkyard turbo car with a rebuilt mopar 782 head on it.

[88_pacifica]

Wow, I just don't know. I know that means jack squat and doesn't help any, but I really don't know. In my years of GM experience and such I'd have to think it is a temp related thing though vs defective parts/material. If you have the equipment get a PRECISE reading of the lower plane of the head. There will probably be some warping on the exhaust side which would lead me to believe that the quench area was the hot side which would confirm a head running too hot. If not, then you'd have to keep checking. Being the short distances you drive, I wouldn't think it's high RPM sustained abuse... sorry I couldn't help more. :(

[tryingbe]

Well, so far I gather, detonation + heat

Here's what I plan to do to prevent it happening again.

New engine, I think the cam, rockers, and lifters are savlagable...
New radiator + new hoses
Manaul fan swtich, no more computer deciding to turn the fan on or not.
EGT, wideband, water temperature, oil pressure, volt meter, fuel pressure etc... aftermarket guage
Install a tranny with 3.5 FD instead of 3.85. Roughly 10% reducing in revs
Install bigger tires when the time comes
New knock sensor and wiring
Drive slower on highway
Decode the cal and see if it anything wrong
Send in injectors for flow test and cleaning
New adjustable fuel pressure regulator
Underbody plate to decrease drag
4 cylinder cooling mod to improve cooling abilities
2005 gasket

Now, time to sell stuff to support the goal..

[cordes]

Wow, that is really throwing parts at it. I would formulate a little more attainable goal to start, especially if most of the parts are fairly new.

[turbovanman²]

I agree, you don't need a new engine. Reuse the pistons, put some new rings in, resurface the head. Have the injectors checked and put your stock cal back in and see what happens.

[88_pacifica]

Now wait Harry, Simon is right. Don't go throwing crazy money at the problem yet with a good exisitng base like you have already. I would do exactly as Simon says, but I don't know if I would reuse the head because of the depth of the pitting and damaged edges. Plus, you really would have to make sure it isn't warped at all and that it doesn't have very small existing stress fractures. You could go and have it magnafluxed, shaved, etc. but it is usually cheaper to get another "seasoned" head that has been through the thermal cycle process already and use it.


Well, so far I gather, detonation + heat

Here's what I plan to do to prevent it happening again.

New engine-just rebuild this one, I think the cam, rockers, and lifters are savlagable...-agreed
New radiator-not necessarily-get profess flushed+ new hoses-agreed
Manaul fan swtich, no more computer deciding to turn the fan on or not.-not necessary with aftermarket cal- reprogram on/off turn on setting to your preset range- TU should do this for a nominal charge if not free
EGT, wideband, water temperature, oil pressure, volt meter, fuel pressure etc... aftermarket guage-agreed
Install a tranny with 3.5 FD instead of 3.85. Roughly 10% reducing in revs- depends on your goals of top-end or 1/4 mi performance and MPG goals
Install bigger tires when the time comes-why?
New knock sensor and wiring-not necessarily
Drive slower on highway- not necessary- shouldn't make a difference
Decode the cal and see if it anything wrong-definitely
Send in injectors for flow test and cleaning-Mr Injector-$65 tops
New adjustable fuel pressure regulator-agreed
Underbody plate to decrease drag -not necessary except for extreme race/performance improvements top-end 200+ mph(adds weight)
4 cylinder cooling mod to improve cooling abilitiesnot recommended- leave stock and do not clip fins- You're in AZ and it should be sufficient if the cooling system has been thoroughly flushed regularly and WELL!
2005 gasket-agreed

Now, time to sell stuff to support the goal..-maybe

The reason I am telling you this is because you're at wit's end and pissed that this happened so you're having a "knee-jerk" reaction.:confused: Been there, done that with many a GM.:amen: :D So, simmer down a bit and look at this list. :p I'm sure that a lot of your existing stuff can be reclaimed to reuse for the next rebuild. Just chalk this up as not nevessarily parts failure, but rather not having the necessary gauges. Being that you're in AZ you're considered to be in one of the more stressful temperature ranges from pretty cold to damn hot. So, do what you already know and try it again with what you've got. If anything just get some good gauges and all will be good in the "desert" :D:thumb:

[tryingbe]

New engine-just rebuild this one, I think the cam, rockers, and lifters are savlagable...-agreed
The damage on head on cylinder 1 is really deep. Don't want to use it.
Have to take the engine part on the weekend to determine if I want to reuse the block/pistons *doubtful*

New radiator-not necessarily-get profess flushed+ new hoses-agreed
I have a re-core radiator I got for $80. No point of using the currect rusty one, oilly I have.

Manaul fan swtich, no more computer deciding to turn the fan on or not.-not necessary with aftermarket cal- reprogram on/off turn on setting to your preset range- TU should do this for a nominal charge if not free
Tried that, don't like it. Fan will not until it rearch a very high temperature while the car is in motion. Beside, don't want to pay shipping bothway nor wait after the current list of cals are done and then have to wait on the "fix me" cal list.

EGT, wideband, water temperature, oil pressure, volt meter, fuel pressure etc... aftermarket guage-agreed

Install a tranny with 3.5 FD instead of 3.85. Roughly 10% reducing in revs- depends on your goals of top-end or 1/4 mi performance and MPG goals
I want a all around car, going 70mpg at 3.5RPM where the red line is 6000rpm doesn't quality to me as one. Only got 28mph max on the GLH vs 31 mpg on Daytona. Beside, I like the shift feel on A555/A520 than my current A568.

Install bigger tires when the time comes-why?
Increase gasmilage and traction while decrease rev at the same time.

New knock sensor and wiring-not necessarily
Better safe than sorry... again.

Drive slower on highway- not necessary- shouldn't make a difference

Decode the cal and see if it anything wrong-definitely

Send in injectors for flow test and cleaning-Mr Injector-$65 tops

New adjustable fuel pressure regulator-agreed

Underbody plate to decrease drag -not necessary except for extreme race/performance improvements top-end 200+ mph(adds weight)
It addes weight but it will improve gasmilage because of drag.

4 cylinder cooling mod to improve cooling abilitiesnot recommended- leave stock and do not clip fins- You're in AZ and it should be sufficient if the cooling system has been thoroughly flushed regularly and WELL!
Not planning to clip fins, I want to have a cooler source of coolant going to 4th cylinder. Where did you read this procedure is not recommanded?

2005 gasket-agreed

[88_pacifica]

I agree with everything and see now that you already have a slew of parts on the shelf. I wasn't sure you had all that stuff already. I definitely agree on the cal. It really sucks Chris is backlogged so bad and moving so slow. :( Not too sure about the tires though. In theory you're right, but with the added weight(minimal) and the added surface area(again, minimal) it would probably offset you're mileage gain(minimal), otherwise trucks would get like 50 mpg. However it takes more power to turn those bigger tires. To be honest I'm not 100% sure about that one. As for the clipping of the fins. I did a thread on TD that everybody chimed in on that I'll have to find, and I think Simon and everybody else said it wasn't a good idea at least with a U/D and tough conditions. I know you may not run a U/D but if it regularly gets 100* or better, you need to reduce any cavitation. SOmebody else may have a second opinion on this. But, in conclusion, I think you're smart to not reuse the head. Not sure on the pistons, since I never saw them, and the block is probably ok since that is a stronger material than the moving parts, unless there's scoring, etc. it will have to be mic'd to be sure, but you already know this. :D Again, good luck...

[tryingbe]

If the bigger tires doesn't do anything other than lower the rev by 2%, that is still worth it by itself.

No, I'm not planning to clip the waterpump, no way.

Block was damaged, didn't have heart to find out how bad it was last week, but I guess I'll be doing that this week.


Yes, I have a LOT of spare parts.

[cordes]

Taller tires on an omni won't be worth the minimal ammount of reduced revs. You will be working a lot harder to move the added rotating mass, thereby making the motor work harder under most conditions. Not to mention the fact that braking will suffer.

I make my own cals based on Geoff's blueberry code, and I got 38MPG in the way from detroit to IL in a helacious rainstorm. I have the fan come on at 195* and it won't turn off until it gets below 180*, so it pretty much stays on. I can now idle in 96* traffic for over an hour straight with no ill effects.

I think you are focusing on the absolute last things you should do to cool the car under severe conditions, and that you will be fine with a car that is running well. After all one of the reasons that we haven't the foggiest what went wrong is due to the lack of intrumentation, which will hopefully be taken care of before the underbody clading that will improve the aerodynamics of the bottom side of the car.

[tryingbe]

Care enough to show your blueberry way?

[cordes]

Care enough to show your blueberry way?

Not a problem. I have to go lift, but I will post up the values I have modded for the fan when I get back.

[cordes]

Ok, it is really pertty simple. I think that there is an article on how to do just about every thing on moparchem.com, so I will quickly lay out what you need to do to adjust the fan controls. There are several ways to do it, but I prefer to just edit it in chem, as it is the easiest for me.

First I open chem, and then load my cal file. Then scroll down to the fanoffbelow 45, fanonbelow45 etc. tables. I make the fan come on and off at the same temp regardless of vehicle speed.


Now open up your windows calculator that comes with every PC. If you switch the calculator to scientific mode, you will be all set. The cal uses hexadecimal code for many of the calculations. It is simply a base 16 system (our standard clock is a base 12 for hours for example). Now you can toggle between dec and hex to convert regular #s to hex. If you want to keep the fan on all the time, just make it the valvues B4 which will probably turn it on a little before 180*.

It is all quite simple, you just need to read all you can, and take your time.

You can check out the custom cal how to on my site, and moparchem.com for more info.

[88_pacifica]

good info here ^^^ I can't wait to learn all there is to learn about cals... just over my head at this point still. :(

[tryingbe]

cordes

Thanks, I'll be checking all the custom cal stuff this week.

[cordes]

cordes

Thanks, I'll be checking all the custom cal stuff this week.

yeah, it looks like moparchem.com is down again. Last time it was down for about a week or so before it was back up. Hopefully that will be the case again.

[TurboJerry]

Looks like aluminum swap between the head and pistons..... Running very high temperatures, and detonation..... (even though it probably ran cool on the coolant temp gauge) The rings must be ruined which explains the heavy oil deposits. (could be guides/seals too?) I recomend always running atleast an A/F gauge on a 3bar setup because you never know. (even with stock boost) Or atleast go for a drive with a scanner hooked up to make sure it's close.....

[turbovanman²]

The pistons and block are reusable, I melted my head and scorched my pistons so I rerung it and put another head on.

As for running hot when moving, a manual or lower turn on for the fan won't cure that. You need to find out why its running hot when your moving. Also, if you hook up the manual switch properly, you still have computer control incase you forget.

[TurboJerry]

+1. Just make sure the ring lands are still good, and glass bead the skirts to remove any steel from possible metal contamination in the oil.....

[tryingbe]

All four pistons have the same type of damage, number 1 in the picture was the worst. Ring lands are fine, going to take the pistons and block to the machine shop tomorrow and see what they think.

[tryingbe]

Block is already +40, so that's a big paper weight.

Looks like I'll be starting the short block all over again.

[88_pacifica]

oh man, that sucks Harry... at least you got the parts to do it right! Now just get those guages and you're ready to rock. :thumb::D

[turbovanman²]

Block is already +40, so that's a big paper weight.

Looks like I'll be starting the short block all over again.


Whats wrong with the block?

[tryingbe]

It's bore to the max and has up and down cylinder wall damage.