Collapsed Piston Skirts After Head Gasket Failure.

[Shaun]

Gday,

Im just after a bit of advice from people with experience in this area.

My rebuilt RB26 blew a headgasket on a dyno, and on inspection of the bearings, it was apparent that detonation had occurred in most of the cylinders. (The crank had picked up bearing material, and several engine builders have remarked that only detonation could be the cause of this). Number 6 piston had discoloured slightly, and the headgasket let go around number 6 as well, so it had gotten pretty hot in there.

I was hoping i could use the same Venolia pistons as they were only 4 hours old, but the engine builder has said that three of these pistons have "collapsed around the skirts" and that the piston to bore clearence is now too big.

My questions are:

- What does 'collapsed skirts mean'? I assume its contraction or warping of the skirts due to heat???

- What would cause the skirts to collapse?

After the head gasket failure, there was also damage to the bore on number 6. I thought it was due to water corroding the freshly bored block, but i understand that this is rare. Im now wondering if something catastrophic happened on the dyno because this was the only occasion that the engine hit boost in its short life.

Anyway, thanks for any input. At least there wont be a question mark over the used pistons in the rebuild.

Shaun.

[Blitz]

Whatever you do, do not use Venolia again.

They are the worst piston I have ever seen, and the skirts from memory are ridiculously thin - Sadly you are not the first person to have their new Venolia Piston-equipped engine let go.

[GTR1993]

I have hered that when they machine for the oil squierters on the venolia pistons that it weakens the skirt and what you had happen can happen.

[STATUS]

Agreed stay away from the venolia pistons and your tuner to blow a head gasket and pistons means it was detonating hardcore... hardcore enough to show up on even the most rudimentary knock detection devices.

[s13_Skyline_inside]

agreed with all the comments above, really bad for that to happen on a run in tune. and yeh not really a good idea to re-use pistons in my opinon, easpically if this kind of thing has happened to them the clearances would be stuffed

[Beer Baron]

all the above is sound info. and I'm sorry your engine didn't last I remeber when you were collecting parts for this build and it sounded awesome. I hope you can get it back together better than every

[Shaun]

all the above is sound info. and I'm sorry your engine didn't last I remeber when you were collecting parts for this build and it sounded awesome. I hope you can get it back together better than every

Thanks for all the advice above. I was never really happy with the Venolia choice; finances controlled that choice unfortunately. Ive got CP pistons now and I believe they are better.

Ive had nothing but bad luck with this build; businesses have failed half way through, my new engine failed on a highly respected tuners' dyno etc etc.

I cant understand how this tuner missed detonation because it must have been huge; and they have turned out some awesome cars.

Anyway, hopefully this will be the last time; its been a long time coming.

Shaun.

[Gts-t]

Good luck with it shaun, im sure u will get it going as good as that engine bay looks

[GTR-32U]

please PM me and let me know who your tuner was...Any experienced tuner worth his salt should have picked that sort of detonation long before it eventuated into that.And on a run in tune ??? what the hell was he thinking ? Run in tune is supposed to be very ,VERY delicate basically setting the fuel so its not really rich but more importantly keeping ignition advance relatively low so you are able to load the engine ( ie 4 heavy guys in top gear going up a hill ) this is the best way to bed the rings in...Sorry to hear about this as your hard earned cash has been totally blown to smithereens by someone who should know better...

[Shaun]

Thanks mate. I agree with what you are saying, but before i start giving out names (even privately), id like to chat with them about it. Ill give them the opportunity to explain what happened, as i dont want to make any enemies.

Im also reluctant because i know this guy is an extremely good tuner and had turned some great cars.

Shaun.