What was wrong with this piston!

[Boost Freak 3]

Okay I bought a galant vr-4 and the guy said that it had rod knock and that you could move the piston back and fourth. well I looked at it and it did move back and fourth more then is should. It was the fourht piston in the block. I pulled the piston and this is what it looked like. What do you think was wrong?

Those are both sides and the top. Its jsut this one piston. Do you think this piston is reusable.

 

[Jake30]

Piston slap... Usually when the cylinder walls are a bit larger than the piston and out of spec, the piston slaps a lot more. This happens with wear overtime or improper machining/assembly.

 

[Boost Freak 3]

What should I do just replace bearings and rings. Im really new and trying to learn so sorry for so many qustions.

 

[pedrick1]

Well if it is piston slap then that means your cylinder is too large for that piston, so you might have to pull all the pistons, hone all the cylinders and go a size over on new pistons. This also could have been from oil starvation seeing as the last cylinder to get oil is the 4th, after everything else, balance shafts pistons 1,2,3 etc. How was the oil pressure when the car ran do you know? And if the rod was knocking then check your crankshaft, that journal might be spun and the crankshaft ruined, just happened to me about a month ago. Have any questions just pm me

 

[Defiant]

That piston's scrap. Whether the others are as well is iffy. Figure on a complete rebuild with new pistons.
I'd guess over-pressure and leakage past the rings, or detonation causing ring failure. How rough on the car were the previous owners? Is the oil jet for #4 broken off?

 

[Talesin]

Looks like those pistons may have kissed the valves a few times at some point in the past, too... looks like it has the little impact crescents, and not just the cast-in clearance insets. I'd replace them completely if it was my engine.

I'd also lean toward excessive piston slap rather than blowby knock or detonation.. that'd likely crack one of the ring lands at least, if not take out a chunk of the land with it.

 

[PSITSI]

Looks to me like you now have 4 lovely paperweights. Put new pistons and rings in. You can get regular old stock pistons cheap. I would recommend checking your bore size before you go ordering anything. You will probably be better off having the block bored and going with an oversized piston.

 

[Boost Freak 3]

I looked at the pistons a little more closely today and on the piston near the ring its cracked the its a big chunk that you could pull out which sucks. Also I found it on another one to. The piston squirters seem to be fine. He didnt say anything the oil to me. When I checked the oil to see how much I was going to drain it was below, Below. But from what he said the car sat for like 6 months.

Im going to go check out the car tomorrow a little more closley. I will take pics and post them. Im going to get new pistons and rings. Im short on money thats my only problem.

 

[perley03]

You guys are only forgetting one thing, and that boring out a motor and ordering new pistons, you have to order the pistons and bring them with you to the machine shop so the machinist can figure the piston-to-wall clearance, if you want to build the motor right. You just can't bore it over .010 or so and call up the company and order +.010" pistons, your clearances will be way off, and if its too far off, you will be in the same boat as above. Do it right and do it once.

 

[Jake30]

You guys are only forgetting one thing, and that boring out a motor and ordering new pistons, you have to order the pistons and bring them with you to the machine shop so the machinist can figure the piston-to-wall clearance, if you want to build the motor right. You just can't bore it over .010 or so and call up the company and order +.010" pistons, your clearances will be way off, and if its too far off, you will be in the same boat as above. Do it right and do it once.

Thats why you take the block to the machine shop... Have them figure out how much it needs to be over bored, order the pistons, when you get the pistons, take them in and then have the block machined.

 

[architechnik]

Jake, your logic astounds me.
Boost Freak, I hope you weren't hoping for a quick fix! It's gonna be some time before you'll be able to get that engine up to shape.

You may want to check the crankshaft while you've got all these parts out... with as much abuse as that piston has been given, there may be some adverse effects on the other end.

Speaking of the valve gouges, you might want to check the top end too... dammit, just rebuild the whole thing.

 

[98Bl4ckGST]

time for a rebuild, or buy a 'pre-built' off the shelf block from your favorite dsm shop.