NA Track Car

Discussion in 'Member's Garage' started by Peter Black, Feb 11, 2011.

  1. tatty000

    tatty000 New Member

    I seen the exact same thing happen. It was from poor rebuild work, which caused the nut, I presume, on the journal thingy that attaches the piston thingy with the bearings, yeah, that probably wasn't done up right and slipped out. Or poor oil distribution to a piston journal would do it.
  2. Peter Black

    Peter Black Active Member

    The nut came off with a decent chunk of sheared stud still in it, not sure if it's a cause or collateral damage, it's pretty beaten up but that could have happened after it broke off easily enough.

    The engine stand is good too, the rod to turn the engine over with is too short for something heavy like a VG but the longer one from the crane does the trick.

  3. dieseldave

    dieseldave Well-Known Member

    The resolution of the camera is fine, just a little closer. As far as the follow up damage, I can normally sort out what is what. Remeber this is one of the main skills in my day job, ;) At least you are not trying to cover up what happen, just work it out.
    If it is a brittle fracture then I would say over speeding of the engine. Check the main bearings and piston tops they will give away if it is due to repetative bouncing off the limiter. Or a singular over speed such as changing to first when doing 100km/hr (belive me some people do it, just check you tube).
  4. Tektrader

    Tektrader Z32 Hoe, service me baby

    Jaydee in Bayswater have wire, connectors, switches etc etc
  5. Chrispy

    Chrispy Pretentious Upstart

    It's out of the car, just have to pull the inner tie rods off and I can send it to you :)
  6. Peter Black

    Peter Black Active Member

    Thanks, we're getting towards the putting stuff back together stage!

    I'll sort out some more pictures when I get some time, hopefully in the next couple of days. I should pull the whole engine to bits just as a learning exercise I think.
  7. Blipman

    Blipman Beer hooves totally work

    I don't think overspeeding has taken place, there really wasn't much of a hoon vibe from the guy it was bought from (possibly a bit of a dishonesty vibe though in retrospect!), and there was a lot of water in there, be it from flooding (still my vote) or a head problem etc. If there was overspeeding that caused the rod to break the piston is still where it should be (just not moving) and so I don't see how that would have caused all the water to get into there. On the other hand it looks like things did shatter rather than bend first, if that says anything.

    I've done a good 9,000rpm or so in my first Z without incident and it's got to be hard to do more than that... I was coming up to the end of Sandown straight at 200kph with no brakes, so you do what you have to do :) They are shot peened from the factory from memory.

    Not shown in the pics Peter posted was the break here on the left... not sure if that sheds any more light on things.

  8. Peter Black

    Peter Black Active Member

    Thanks Ben, after I posted the pictures I realized none show the break on the left in that picture, it's actually broken in 2 places, the obvious one there and a lesser break above it and to the right slightly, near the large black bolt in that picture.

    I kind of didn't get a hoon vibe from the guy we got it from but as Ben said, there was a big chunk of dishonesty so you never can tell. Would driving it for a long time with a dead head gasket do this? There is definitely no shortage of neglect apparent.
  9. Tektrader

    Tektrader Z32 Hoe, service me baby

    So the girdle broke. You usually only see that on big H.P. engines.

    Did the rod let go and smash the girdle? Probably more likely.
  10. dieseldave

    dieseldave Well-Known Member

    Tekkie I think you will find that was from the conrod.
    Ben, there is nothing saying he didn't spin it to higher than 9k saying that the detail inspection of the fracture will show. I suspect that the top of the piston too. Also it might be a combined thing. If it is a hydralic lock the fracture in to three piece like that coan only be achieved if bent along the rotational axis.
  11. Peter Black

    Peter Black Active Member

    I'll get you some pictures tonight or tomorrow Dave. I'm strongly against the hydrolock theory now, pod filter is too dry and dusty and there is lots of nasty much in the sump along with a couple of litres of rusty water.
  12. Jinxed

    Jinxed Moderator

    the car was in the floods right? plus its got a hole in the block, so the water would have gone in through the hole in the block when the floods came through..........
  13. Peter Black

    Peter Black Active Member

    That's possible, we were told it was rained in with the windows open so the ECU got wet and the starter motor died which is why it was not starting so we know we can't believe what we have been told about it.

    You do make a good point about water being able to get in the sump through the hole. The dusty pod filter still kills the hydrolock theory for me though.

  14. dieseldave

    dieseldave Well-Known Member

    I get the floods part now. I assumed that they meant it failed when the car was in the floods, it was runnig at the time. If this is the case. Overspeed is the main culprit still, (depending on photo confirmation). And the water in the oil could be from the flood water the head gasket, etc.
  15. Peter Black

    Peter Black Active Member

    Broken rod:


    Damaged girdle on one side:


    And girdle completely smashed away on the other side:

  16. dieseldave

    dieseldave Well-Known Member

    Easy one. It is a failure in tension. There is clearly some necking to the centre of the conrod, that looks like it is machined but it is a change to the material so I think in split second timing it happened over maybe two or three revolutions. Which is consistent with an over speed.
    Before we get people going the conrod is bent, it is definitely a hydraulic lock or detonation. I thing you will find that has happened afterwards. The bend angle is too great for it to occur, it is clear the edge of the far side (in the first photo) has striked somethin on its end (note the 45degree champher). This is most likely the girdle. Also look at the close edge of the fracture on the conrod and you will see the shinny edge it is clear this has been punching through something, repeatatively. I suggest that the sump and baffle plates, and the girdle parts have copped a flogging.
    Finally the giveway of the failure is the failure along the crystaline structure of the metal. This was a serious over speed, I suggest that if you check the other conrods you will find that they are longer than standard.
    To use that technical term, the FFFF. Check for spun bearings and piston to valve contact. It is very hard to do this to the VG30 the NA is very tough.
  17. mungyz

    mungyz Well-Known Member

    If you chuck in some water and bend the rod the rod is now too short for the piston to travel to the end of the cranks stroke (it will hit the bottom of the bore) this then puts the bent rod in to tension and twist at the same time (one side of the piston bottoms out before the other) = BOOM!! I doubt it was over speed that did this - stock ECU in there?

    It could have been over revved but that's pretty uncommon and the water in the intake is very common.
  18. Peter Black

    Peter Black Active Member

    Thanks Dave, I bought this knowing there was a good chance I was just buying a rolling shell and the price I paid was suitable for that so I'm not concerned at all as to how dead the engine is, though I must admit I'm happy it seems to have died in some kind of interesting and catastrophic way. Hopefully I'll get some interesting paperweights out of it.

    Checking for valve to piston contact seems pretty straight forward, how do I check for spun bearings?

    I think I might strip this engine right down to it's component parts as if I intended to put it back together just as a learning excercize, that way if I get it wrong somehow on this one nothing is lost and I'll know better when I'm working on an engine that matters.

    I'm sort of playing with the idea of de-turboing a VQ30DET at the moment too.

    Still not sold on water in the intake due to the dusty pod filter, could a head gasket failure get enough coolant into the combustion chamber to hydrolock it?

    Not sure about the ECU on this one, the guy I bought it from had only had it a couple of months, he swapped the ECU from another NA Zed into it. He told us he did it because the previous owner installed some kind of chip in the ECU for this car and tried to do it with a self tapping screw!!! As has been previously mentioned everything this guy said to us has to be taken with a huge grain of salt, quite a bit of it has been proven outright lies already. It also has something spliced to the loom just near the AFM plug which seems suspiciously like one of those Ebay +15hp things so I would not put it past some of the previous owners tpo have done some pretty abusive stuff to it.
  19. Blipman

    Blipman Beer hooves totally work

    Is there a carbon cannister removal tech article anywhere? Or do we just need to join up some hoses at the fuel tank? Aside from a bit of smell is there any convincing reason not to get rid of it?

  20. dieseldave

    dieseldave Well-Known Member

    Look both Mungy and I might be right or wrong, but in reality it is semantics as the end result the engine is fcuked. All of the conrod are not recoverable as they will have suffered similar loads.
    To check for spun bearings you need to take off the main caps on teh crank and big ends on the conrod.

Share This Page