Distrb - September 9, 2009 10:58 PM (GMT)
Figured i should update this since i've had it running.
Started up and ran fine, purrs like a kitten even, like it was meant to be.
After doing a large global pull of timing across the map (i am using the Ljetro power fc, so it has a very n/a base tune) , we took it out for some road tuning, mostly off to 1~2psi boost (thanks to adjustable actuator arm) at light load to make sure things were going well. which they were. Very smooth, very responsive. The low down torque was great.
Ok time for some higher load runs. Give it about 1/2 throttle. gets to just over 5500rpm and my mate with the knock headset yells at me to back the f**k out of the throttle. Just as i lift off and pull out of gear, a small pinging noise is heard, and the car shuts down completely.
The noise that was heard on the headset was apparently metal on metal. NOT good.
So ended up getting a flat tow back home (was tuning less than a km from my house) pushed it into the shed and decided to do a bit of a compression test. So whipped all coils out, and all plugs out. When i got to the plug on cylinder number 2, it was ultra tight and took ages to wind out. When i got it out, i knew i had found the problem
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notice the lovely gouge mark across where the tip should be. Looks real like the edge of a valve to me. Cann the compression test. its obvious i've located the problem.
Whip the throttle body off, and i find this a whole heap of alloy shavings in the base of it (the coolant was what got in there when i pulled the lines to the throttlebody off)
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Get the whole inlet off. heres a pic looking towards the inlet valves of number 2 cyl
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well what was inlet valves on number 2, both heads are non existent. If i look down the inlets to the rest of the cylinders, everything is fine. hmmm weird.
So whip off the exhaust manifold, turbo and all other bits keeping the engine on, and this is what i find.
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Number 2 bore is obviously where all the action happened. so heres a closeup on it.
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Theres bits of valve sitting on top of the piston, bits of valveseat, all sort of shavings. Piston has taken a hammering, the bore is nicely scored. hard to tell what exactly has gone on other than merry hell has broken loose. Number 3 piston has taken a bit of a hammering too.
So lets have a look at the head. Dare i lift it up and see whats happened here. well the head looks to be fine, apart from number 2 cyl, which looks a little something like
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top left you can see thats an exhaust valve head actually turned around and trying to make its way back out where the inlet valve used to live. It is wedged in there quite solidly. Suffice to say the head is toast.
To recap, damage sits something like:
2 x Piston
1 x Head
1 x Block
(possibly 1 rod, depends what else i find when i pull the block out and strip it down this weekend)
Now what im sure you are all wondering is how did this all happen? Well on closer inspection on the cylinders that survived mostly (i.e. 1&4) the piston shows signs of the valves just nicking the edge of the flycut, maybe .5mm at the absolute most. So clearly the failure is caused by piston hitting valve, this is obviously the noise that was heard through the headset.
Obviously at light throttle this wasnt a problem, as vvti wasnt advancing very much. But when the cam advances (it makes a large advance at around 5000rpm) is when this problem occours. There is no problem sans vvti advance, so at the end of the day the failure is mine, for not taking into account the extra timing advance that vvt-i brings during the measuring and mocking up stage of this build.
The obvious fix to this issue to allow the 2jz piston to be used, is to flycut the extra tiny amount to allow the valves to clear on full cam advance, so i am pretty confident these can still be used.
Obviously this sucks alot, but it is me who has made the mistake and it has cost me bigtime. I am very lucky that there was no damage to my turbo, as that would have pulled curtains on this project for good. So i'm just going to suck it up and wear it, coz theres nothing else i can do for now. If anyone has a spare block and or head complete for reasonable money, i'd like to hear from you, so i can get this build restarted.
As per the first post, i am posting this here in the hope that all reading can learn from this experience, not just me. As they say, smart people learn from their mistakes, but clever people learn from the mistakes of others.
Thanks for reading
Andrew