Engine failed on dyno - looking for opinions

[nuggets]

I took my car to a performance shop to have them program my new AEM ECU and to tune it. They got the car started and idling great but then on the dyno it started to push coolant but they said that it never overheated (they shut it down in time). They said that they weren't boosting at the time (had boost at 0 during the initial runs). Claimed that the car still ran afterward, albeit pushing coolant and running rough - they thought that a cylinder or two may not firing.

I had it towed to another mechanic to have him diagnose and fix the problem (the performance shop said that they wouldn't do the engine work). He couldn't get the car started and couldn't figure out why. The performance shop claimed that it started with no problems before I towed the car. The mechanic couldn't find any problems so he removed the head and found that all the cylinder walls had scuffing and striping. The scuffing is worse on the exhaust side. He also said that the block is bowed straight down the middle, lengthways, between each piston. It's a small valley but large enough to not allow a MHG to seal. However, the head checked out ok - no warpage. He said that the MHG looked ok too. Said that the head studs were not loose.

I need to get this repaired but I'm asking for opinions on what may have happened here. The mechanic says that he doesn't understand how and when it failed. He thinks the scuffing may have occurred over time but the striping, warped block, and supposed gasket failure is a mystery. His initial thoughts are either the machine shop did poor work on the block (they installed the pistons and rods too) or there was an extraordinary heat event that caused this damage.

A little background on the engine:

completely rebuilt about 6,000 miles ago and ran great up until this point. The rebuild consisted of many things including:
- JE pistons 84MM bore (purchased from Reg Reimer w/ his custom spec's: offset pin, 10 thou raised pin, dropped 1st and 2nd ring land, stronger lands, chamfered skirt)
- Toyota piston rings
- ARP head studs, rod bolts, mains
- stock rods
- 1MM oversize valves
- head and block tested, machined, blueprinted.
- Cometic 1.5MM MHG
- Stock Toyota ECU w/ Apexi SAFC2 and Greddy boost controller
- 550 injector / lexus AFM mod.
- walbro fuel pump, Aeromotive AFPR.
- car was tuned by a shop on a dyno.

Then I upgraded a few things before this recent tune (car was not running after these upgrades - I had it towed to the performance shop for them to program the AEM and tune it):
- AEM ECU
- removed AFM, installed MAP sensor
- SupraSport BOSS turbo
- 850cc siemens injectors from Driftmotion
- ATI super damper
- rewired injectors for sequential ignition and did the DH61 ignitor mod.
- PLX wideband and EGT sensors

Attached are pics of the block (head pics in the following post).

Anyone think they know what caused this? Thanks.

 

[nuggets]

Pics of the head:

 

[toyotanos]

That looks amazingly similar to my head/block! Guess what mine did- I lifted my head on the exhaust side. All 6 cyls leaking pressure to coolant and to each other. My cause was head studs that were not tight (likely from the head getting hot) but yours might be different? Did you check the head studs' torque before pulling the head off?

As for the scuffing, I'm not sure what would have caused that. I'll have to defer to someone more knowledgeable in forensic teardowns.

 

[nuggets]

Ooof. All 6 cylinders.

I asked him to check the head studs before he removed the head and he said that they were tight. I don't know if tight meant not loose or torqued to spec. I'll confirm with him.

 

[TweeT91109]

did you put the head through heat cycles and re-torque afterwards....I believe it needs to be done about 5 times to get the MLS to properly seal.

 

[nuggets]

I followed ARP's torque instructions and used their lube however I did NOT heat cycle and re-torque . (When I built the engine 7 years ago I didn't know about the cycling/retorque procedure. When I found out about the procedure I already had plenty of miles on it without incident so I figured that I was ok)

Do you think that the engine could last for ~6,000 miles before the bolts became loose enough to cause this?

 

[toyotanos]

I re-torqued my studs 2 times-first after 6/7 heat cycles, then about a year later (~1000 miles). My engine went 3000 miles without issue, but it got hot when I was driving on the track for Powercruise and I suspect that's when they initially started to get loose.

 

[destrux]

Scuffing in the cylinders only happens for one of 4 reasons (barring assembly errors or oil contamination)...

1. Pistons over-expand from too much heat and "run out of clearance".
2. Lack of oil (should have damaged other things)
3. Damage to the piston from detonation
4. Coolant in the cylinder (coolant doesn't lubricate cylinder walls very well)

I've never seen a head lift on a turbo car that was running no boost unless it's detonation related (low fuel quality, way too lean or too much advance), so if the bolts didn't come loose and the head did lift... I'd be looking into why.

If the head bolts were loose I would think the mechanic who tore down the engine would have noted that (did he?). When I tear down an engine I use a torque wrench (set on reverse) to look for bolts that were loose. Even without that though, I would notice if a head bolt takes ~40 ft lbs to remove instead of ~75 (with breaking torque usually being even higher on a bolt that hasn't moved recently).

I'm not going to say it was anyone's fault, because without tearing it down myself or being there while it was tuned, I don't know. This is just my opinion on a few things you mentioned.

 

[mk3_7m]

I think the scruffing could come from the improper cylinder wall clearances since forged pistons expand differently to cast pistons.

but there's many other factors to it as well.

Sorrie to hear about your loss >.<

 

[nuggets]

I just heard from my mechanic and he said that the reverse torque on the studs ranged from 89ft lbs to 86 ft lbs. ARP spec is 90ft lb's if I recall correctly.

As far as oil goes, the cams and journals looked fine...I'd imagine that if there was a lubrication problem we'd see something there too (correct?).

Two other things that I should say is as far as coolant goes, the mechanic said that he checked my oil and took out the plugs to look down the cylinders and could see no evidence of coolant in the oil or coolant pooled in the piston dishes. Maybe the coolant burned off?

Two big head scratchers for me are 1) why did the car not start after it was moved to the mechanic's shop. Even with this damage, I'd imagine that she'd still start. 2) the block was warped but not the head. I would have thought for sure that the head would warp.

 

[nuggets]

Thanks for the opinions and input. The mechanic is going to tear it down to check the clearances in order to rule out poor machine shop work. Regardless, looks like I have to make a decision to dump more money into it or give up and part it out.

 

[NashMan]

ya you need to see it all befor the mighty finger gets pointed some were

 

[Moy]

another note is that it looks like the head wasn't machined smooth enough, I can see ridges from where the machine (or person) milled the head...

 

[Devin LeBlanc]

Cylinder wall scoring could be caused by to rich washing out the cylinder wall's.

 

[NashMan]

I say tell it's all part it all here say