My 26/30 Is Rooted

[GTRNUR]

Definatly not detonation in my opinion. The picture that shows the damage to the head clearly shows impact marks.

The three marks to the left are quite deep, and probably wont clean up when the head is shaved ( not that that is important as they are in the squish pad area anyway).

The mark in the middle is also very deep, and shaped oddly. Such a shape would require an existing flaw to exist in the casting of the head for detonation to produce that shape... It just cant happen.

Last of all, is the big dents to the right ad the edge of the squish pad. The foreign material impact has clearly distorted the aluminium. Detonation just wouldnt do this.

You may never find the cause of the damage. I'd be looking at your turbo compressor wheel, and inside your intercooler next. You might find a trace of something. Really though, I suspect the foreign body entered the engine as one stray particly, and then was smashed up into smaller particles before it left the engine via the exhaust ports.

Depending on the size of the particle it could have contributed to the rod bearing failure. Having oil diluted with petrol (and its reduced lubricating capability) combined with the additional rod bearing pressure created by the foreign particles resulted in the failure.

[mrsparkle]

+1 GTRNUR

I had almost identical marks on a RB25 that i pulled apart that had a knock (or so i thought) - Turns out i had lost part of my compressor wheel. If i had to guess you have had a slighty bigger particle or particles that have been in there at big rpm and have been enough to damage the bearings.

[Swiper the Fox]

Definatly not detonation in my opinion. The picture that shows the damage to the head clearly shows impact marks.

The three marks to the left are quite deep, and probably wont clean up when the head is shaved ( not that that is important as they are in the squish pad area anyway).

The mark in the middle is also very deep, and shaped oddly. Such a shape would require an existing flaw to exist in the casting of the head for detonation to produce that shape... It just cant happen.

Last of all, is the big dents to the right ad the edge of the squish pad. The foreign material impact has clearly distorted the aluminium. Detonation just wouldnt do this.

You may never find the cause of the damage. I'd be looking at your turbo compressor wheel, and inside your intercooler next. You might find a trace of something. Really though, I suspect the foreign body entered the engine as one stray particly, and then was smashed up into smaller particles before it left the engine via the exhaust ports.

Depending on the size of the particle it could have contributed to the rod bearing failure. Having oil diluted with petrol (and its reduced lubricating capability) combined with the additional rod bearing pressure created by the foreign particles resulted in the failure.

[STATUS]

right guys a further development. looks like we have looking in the wrong place. i now suspect something has gone through the engine.from where i am not sure. below are pictures of the head on number 5 the one that spun and number 5 piston crown,, i was running a 1mm headgasket. question is whatever caused these marks would it be enoug on a 1mm gasket to jam the piston enough to cause the crank to hit the bearing momentarily?.

Looks like a broken ring, valve guide or plug end. Are the rings still complete on No5? check the guide and see if they still protrude fully from the head. (ive had 3 rb26 heads come through with broken guides requiring rebuilds)

Head will be fine with a weld and shave, piston can be reused with bit of creative work, all cheap. If your after huge hp then swap it out but for general duties i would not stress.

[T04GTR]

my head looks way worse than that when my stock turbos went thru it.. skimmed it, marks still there. no dramas running 376kw for 40,000km with out issue. just filles up with carbon anyway.

[T04GTR]

if it wasnt a brank new crank, and not cleaned out (imposible to do with out grubscrewing) a piece of shit becoming dislodged is my best guess. youd be supprised at how much crap get trapped in the crank galleries.

[STATUS]

if it wasnt a brank new crank, and not cleaned out (imposible to do with out grubscrewing) a piece of shit becoming dislodged is my best guess. youd be supprised at how much crap get trapped in the crank galleries.

something like that wont make it from crank galleries to top of piston though.

[ST240]

Damn man the markings on your piston look identical to the ones on one of my pistons in my rb30 longblock (of which im reusing all components lol).

Looks like foreign material for sure. Best of luck to you.

Edited April 13, 2010 by ST240

[T04GTR]

something like that wont make it from crank galleries to top of piston though.

i realise that.

most oils, evan shit ones have a sheer pressure exceeding 200,000psi , way more than it takes to dent a cyl head. so there is no way it would of wiped all the oil from the bearing.

once the bearing is gone... the piston/rod is free the flop up past tdc, and impact the head.

but. every engine failure is uniqe, so im only guessing.

[Mark-32]

Looks like a broken ring, valve guide or plug end. Are the rings still complete on No5? check the guide and see if they still protrude fully from the head. (ive had 3 rb26 heads come through with broken guides requiring rebuilds)

Head will be fine with a weld and shave, piston can be reused with bit of creative work, all cheap. If your after huge hp then swap it out but for general duties i would not stress.

The marks on the piston and head in those pics look nearly identicle to the marks I have on no 4 and no 1 cylinder of my forged rb26 engine.

My engine had just been fully rebuilt and after doing about 500-600km's including dyno time, bent the valve and broke the valve guide in no 4 cylinder.

I realise this is probably the wrong place to ask, but can anyone tell me if this is a common issue with rb26 valve guides even when kept under 8500rpm, and only using 260deg cams?

Is it possible for bits of the broken guide to travel between cylinders? I have the same issue in no 1 cylinder but the guides in that cylinder are fine.

Also, would a broken guide cause the valve to bend? Or is it more likely that the valve bending would have caused the guide to break?

[STATUS]

The marks on the piston and head in those pics look nearly identicle to the marks I have on no 4 and no 1 cylinder of my forged rb26 engine.

My engine had just been fully rebuilt and after doing about 500-600km's including dyno time, bent the valve and broke the valve guide in no 4 cylinder.

I realise this is probably the wrong place to ask, but can anyone tell me if this is a common issue with rb26 valve guides even when kept under 8500rpm, and only using 260deg cams?

Is it possible for bits of the broken guide to travel between cylinders? I have the same issue in no 1 cylinder but the guides in that cylinder are fine.

Also, would a broken guide cause the valve to bend? Or is it more likely that the valve bending would have caused the guide to break?

Usually something jams in the seat and bends the valve then the guide cracks and all hell breaks loose, was it inlet or exhaust guide?

[Mark-32]

Usually something jams in the seat and bends the valve then the guide cracks and all hell breaks loose, was it inlet or exhaust guide?

It was the inlet guide.

I first thought that something must have got sucked into the engine but when we pulled the head off there was nothing to be found except a bent valve and a few little bits of squashed broken guide.

There are no marks on the rear turbo exhaust wheel to indicate anything has got spat out either.

The car did about 20 hours on the dyno being run-in and tuned, and was driven on the road after that for about 3 days with 320rwkw on 13.5 psi with no dramas before this hapend.

Any ideas why this would hapen and what would cause it?

[aerofocker]

piece of the guide jams the valve open and piston bends it

[Mark-32]

But why would the guide break?

[Swiper the Fox]

But why would the guide break?

fatugue...did they fit new guides when doing the engine. I see cracked guides all the time when pulling heads down.

[Mark-32]

Yep they fitted new guides when they did the rebuild.

Thats why it seems strange, the tuner was reving it past 9 grand on the dyno aswell so you would think if it was going to break it would of broke on the dyno.

Duggans balancing in victoria have covered it all under warranty and the head is on its way back to me at the moment so Iam lucky in that respect.

They said the 26 heads dont usualy break guides unless something goes through the engine causing the valve to bend, then in turn breaking the guide.

Its just bloody frustrating as its only a new engine with all new parts, and we had to pull the whole engine and box out of the car again to get the head off.

[Marko R1]

Yep they fitted new guides when they did the rebuild.

Thats why it seems strange, the tuner was reving it past 9 grand on the dyno aswell so you would think if it was going to break it would of broke on the dyno.

Duggans balancing in victoria have covered it all under warranty and the head is on its way back to me at the moment so Iam lucky in that respect.

They said the 26 heads dont usualy break guides unless something goes through the engine causing the valve to bend, then in turn breaking the guide.

Its just bloody frustrating as its only a new engine with all new parts, and we had to pull the whole engine and box out of the car again to get the head off.

I know the feeling of frustration u are experiencing, in fact most of us here can relate

[juggernaut1]

When you've had and engine pulled out and pulled down 3 times before its ever fired up......then you'll have something to complain about.

Second time to instal NEW BEARINGS.....not put back the original bearings Lol.

Third time because I found out they didn't balance it despite requesting it to be done.

[T04GTR]

for stuff to make it into differant cylinders is very posible. ive seen it first hand.

firstly, rear turbine wheel fell of, most of it went out the back but alot went back up the ex manifold and destroyed to bores on 4,5,6. also made it into 1,2,3 but not as bad. it was smashed into the head on all cylinders.

second, at my old work we had out ipra civic drop a ex valve on no,4 that broken exhaust valve ended up in the inlet port of no,1. lol.. motor was a throw away..

[R31Nismoid]

I know the feeling of frustration u are experiencing, in fact most of us here can relate

Indeed, the fun of a full build is... challenging at the best of times

But hey, he got warranty, that's not a bad end of the deal!