Valve through the Piston!

[Mpower280z]

This is unbelievable. Today was an awsome day to fire up any sports car in Chicago. I decided to take my Z for a drive after finally fixing the Toyota brakes (They work great!). I drove it to the local store, but hitched a ride in a tow truck for the journey home. Leaving the parking lot, I was in first gear and had begun to reach for the shifter at about 3.5 thousand rpm. I started to hear a pinging/grinding noise come from the motor which I am not afraid to admit I built myself. As some of you may know this is a fairly fresh motor. Hearing this heart sinking noise, I got on the clutch and she then died on me. I knew whatever that noise was didnt sound good therefore I made no attemt at restarting the car. Thanks to Sprint PCS I was able to get my car towed home for free where I began my disassembly.

I lifted the valve cover and noticed three rockers were off their lash pads. At that point I had a buddy of mine come over to check it out. Neither of us have seen this happen before. An hour of discussion went no where so he left and I proceeded to disassemble. The intake manifold came off next and as I looked into the intake port on the number three cylinder, there was no more intake valve. I then removed the spark plug on that same cylinder and noticed large chunks of alluminum that looked heavily damaged. Time went by and the Head finally came off showing the number three intake valve sunk into the top of the piston and bent almost 90 degrees! I almost pissed myself when I looked at it. I knew it was bad, but not that bad! I was so mad, I was happy! Not only were there chunks of allminum in the number three clyinder, but in numbers six, five, four, and two. There were large amounts in the intake manifold, oil pan, and when I finally removed the engine and disassembled that, there were shavings all over the inside of the block!

So I just finished cleaning all the allumnium out from the block and replaced the piston/rod with one from another motor laying around. I first wanted to ask you guys what you think caused this. Its been driving great for a while now and this just seemed to have come out of no where. Another thing I wanted an opinion on was that I used the number two piston out of the other motor to replace number three on the broken motor, with the bearings from the busted rod/cap (they looked in good shape) is that going to be ok? Because the rockers where out of line, could the cam be bent and need to be replaced? Rockers too? Obviously valves... or should I keep them?? haha. I need to replace the N42 Head (Very badly damaged) so I will be building a new top end. Any precautions before she blows up again?

Just to give you a better idea, I took some pictures of the piston which I will post tomorrow. There were no serious modifacations made to the motor.

[240ZX]

My advise, find a reputable engine builder! :tapemouth

[3RD STRIKE]

I would use a whole set of rods and pistons from the same set.That would insure a better ballanced set. Because they would have the same amount of wear on them. I would not use the bearings, put new ones in it,they are not that costly. I would also have the crank checked to be safe. U might need to have the crank turned. I dont know much about the top end cams etc. maybe some one else can help u on that. good luck.

[beandip]

The cause ? you asked. Sounds like the keepers on the valve came off and the valve dropped into the cylinder. From what what you have said about all the shrapnel in the engine . It needs to be disassembled and a hot tank wouldn't be a bad Idea. Be sure to clean all the oil passages with a cleaning rod like you were cleaning a rifle. And don't reuse the bearings. Is the cylinder walls effected at all ? If not I would be amazed . Like was already mentioned , Have the crank checked along with the rods . You said that in wasn't long since you went through the engine. Did you bore it hone it , or what? With the engine all apart , having it honed and new rings would be a good idea. Providing the cylinder isn't scored. I am sorry for your situation . Gary:rambo:

[Hrududu]

Sounds like the perfect excuse to do a turbo swap to me!

[=Enigma=]

That sucks man. Although I'd like to build my own engine for the experience, this is the very reason that I'm going to pay someone to do it for me. This way if something like this happens, I'll have someone to hold liable and make it right.

[sideshowbob]

This way if something like this happens, I'll have someone to hold liable and make it right.

That doesn't always work out so well. Personal experience here.

Sounds like your keepers stopped keeping and the valve dropped into the chamber, causing all sorts of havoc. It's not too hard to imagine the oil carrying aluminum head chunks throughout the rest of the motor. The fact that they were in the other cylinders, however, points to a seriously bad valve job all across.

[zeiss150]

Just my 2 cents but ... I would go down to the junk yard and pull a new motor. There could be all kinds of problems trying to fix the old one. Dont feel bad either I rebuilt my L24 by myself and it blew up. It wasn't really my fault though the guy that did the head (E88) rebuild did a crappy job. He replaced the bronze valve seats with SS seats but one of them wasn't in good. I was on the freeway and it poped the valve seat which hung the valve down and made contact with the piston and the rocker arm came off and all kind of horrible stuff. sooooo I just pulled an L28 from a ZX, and rebuilt that one myself and its running strong!!!! I wouldn't spend the 3k to have someone build it because stuff can always go wrong and you can get a junk yard engine for about $500 (califonia $'s) Besides isn't building it yourself the whole point of having a Z. Good luck with what ever you decide to do.

Matt-

[Zedrally]

I can only feel for you at this time as exactly the same occurred to me several years ago, there is a thread about it somewhere.

As to what happened, there is a dowel located in the CAM which locates into the CAM SPROCKET. This has moved out of the CAM into the sprocket and possibly into the oil pan.

Hopefully, there is no/little damage to the pistons.

You may be able to rebuild the head (get a head shop to do this) or locata a replacement.

Good Luck.

[Mpower280z]

Never be afraid to build your own engine. My problem was actually not my error. It turned out to be a bad cylinder head... A very bad one. The valve seat found a way to come apart from the head and obstruct the valve from closing. After a couple revolutions, the valve finally broke in half and made itself a nice hole through the top of the piston. Building these engines is actually quite easy.

I did replace all bearings, had the crank checked, and used all rods from the set. The block to my advantage was not damaged! We simply honed it out again and installed the pistons. I completed the entire removal, rebuild, and installation in less than 48 hours. However, I worked on it 45 hours straight.

The results were incredible! I installed a new ported and polished head with another set of valves, but same springs. The difference is unbelievable. I drove it around the block and I cant even begin to tell you how great it ran. I never knew a cylinder head can cause that much damage. I wasnt going to let it ruin my weekend!

By the way, I posted pictures of the disaster in my albums. Be sure to check them out and it might make you feel better about remembering to have the cylinder head CAREFULLY inspected before installation. I also threw in a couple of what the car finally looks like after all this work. It drives, but is still not quite finished.