Damaged Pistons

[Joryn]

Hey all,

A long time ago I reported that I had seen some ridges on the tops of my pistons and I was challenged to bring the pics for some diagnosis. Well I finally got the engine completely torn apart and the sight that met my eyes was not encouraging.

For reference see this thread :
Sharp Piston Edges Thread

#4 cyl was of course the worst, so here's some pics for your diagnosing pleasure:














For reference, from the top it doesn't look too bad at all, slight peaks on the edges where it looks like it was hitting the cylinder wall.

The question I need answered is are these basically brand new pistons (less then 500 miles) toast, or repairable? Pistons 1 and 2 are basically fine, save for some scuffing and #3 is a little worse. Let me know what you guys think.

As an aside, I think the damage was caused by the cylinder bore being too big. I had originally ordered .030" wiseco's from TU, but ended up getting .020"s by mistake. I needed .030" since the block I was planning on using was already .020" over. So I had the pistons taken to a shop and asked if it would meet the clearance specs that came with the pistons. They told me it would be fine, so I told Chris @ TU that I would stick with the .020's (as it would have been another couple months for the .030's).

Apparently the bore was too big and I Ended up with piston slap something fierce. which is what caused the damage that you see. So I'm a little frustrated with the shop that spec'd the clearances. Obviously the next time round I'm plastigauging everything myself heh. Anyways [/rant]

Thanks for the help, any feedback is appreciated

Joe McDonald

[Timmay2]

Well considering theres no way you can properly use them in your existing block... they really should just be tossed. Youd have to get a new block and have it machined for those pistons anyways, and then still end up with pistons that will wear fast on the exposed damage.

Did the block get any damage? If not then cleanup the surfaces and buy the right .030's to go with it.

Did the shop assemble it for you? If they did and stated the clearance would be fine they should be accountable. If they didnt assemble it maybe they were just hoping itd blow and youd bring it in for them to do it lol.

Sorry to hear, no fun.. but its best to start all over now bud.

[86Tona]

The look like ash trays or pencil holders to me. (the latter is my preference). Just polish them up and they'll make some great gifts.

Seriously they are toast. Replace them. These are forged too, right?

[Jackrabbit]

+1 on tossing them.

You wouldn't want to go through all the assembly trouble and have them give out on you in another 500 miles. Find and fix the cause. Rebuild from scratch.

[Joryn]

Yeah the 600 CAD paper weight is definitely looking like the leading option. I should mention that I already have another block that I'm willing to bore to match these pistons exactly, but if they are toast already...well then there isn't much point in matching to these pistons.

With regards to getting new ones, the other 3 aren't nearly as bad as this, would it be worthwhile to get a single (if possible)? Or just get a whole new set?

Thanks,
Joe

Edit: Yes these are forged pistons...hence my serious reluctance to get a new set

[86Tona]

Sorry for your loss. If they're scared then they're toast. You need to figure out what toasted them to prevent the next set from being damaged like these.

[Endo]

OUCH! Definately go after the machine shop for this, atleast try and get them to build your next one for free, if not replace the pistons. Actually come to think of it, try and get them to pay to have a different shop build your next one, because they are obviously idiots. Always always always have the pistons AT THE SHOP when they bore your block so they can exactly match each piston to the bore its going in. Consitering how much extra space they had to smash around in, It makes me very very happy I went with Wiseco's myself, I'm sure any other piston would have fallen to pieces much faster. I bet those were NOISY!

[Joryn]

Quote:

Originally Posted by Endo OUCH! Definately go after the machine shop for this, atleast try and get them to build your next one for free, if not replace the pistons. Actually come to think of it, try and get them to pay to have a different shop build your next one, because they are obviously idiots. Always always always have the pistons AT THE SHOP when they bore your block so they can exactly match each piston to the bore its going in. Consitering how much extra space they had to smash around in, It makes me very very happy I went with Wiseco's myself, I'm sure any other piston would have fallen to pieces much faster. I bet those were NOISY!

You have no idea, at first I had no idea what the noise was...until it was obviously too late. Unfortunately the shop that did the work did it over a year ago so it's unlikely they'll claim any responsibility for what happened (If anyone thinks it's worth a shot let me know heh).

Time to start saving for a new set of forged slugs I guess. I haven't been on here in a while, is there any consensus yet on whether Venolias compare to Wiseco's? Cuz you know, I just love opening a can of worms

Joe

[Endo]

IMO, go Venolia for a drag only car or something you dont mind spending a long time warming up before driving. Wiseco's have the tightest clearance specs for any forged piston i've ever seen, which translates to less time listening to your pistons chatter, and I'd imagine less damage like your pics show, but over a much much longer time frame. They both cost about the same, and look just as beefy side to side. I've never bought Venolia's for myself, so I dont know what thier turn-around time is, but Wiseco took way way way too long for me, when all was said and done the pistons were over 8 weeks late. When it comes down to it, its up to you which to go with, either in my experience are well worth the money.

I recall looking at a thread a while back where someone's block failed around their Wiseco, leaving the piston unscathed. There were pics (maybe someone else can find the thread, I cant) that were absolutely amazing. The block was bowed out about the size of a golf ball at the top of the bore

[phantomrt]

I have Venolia 2.5 pistons with 19,500 miles on the engine. Clearance is set pretty big at about .007". I haven't torn it down to take a look, but it still runs/sounds like it did from day one. It'd be interesting to see. Very low oil consumption, too.

I'm sure the venolia piston -> wall clearance can be snugged up to .0045 without a problem. Although much quieter when warm, there is still noise with the .007" cold clearance. If I build another forged pistoned engine, I would like to try putting the pistons in the oven, set the temperature at 700 degrees, let them warm up, and then measure them with the micrometer to see how much they really do expand.

Back to the subject... I guess I disagree with the excessive clearance alone causing that damage. Reason I say that is because of the scoring close to the wrist pin. When a piston slams back and forth, the part that takes a beating is 90* from the wrist pin. This damage is all the way around.

Also, many engines I have rebuilt had similar piston damage, I have attributed it to debris entering the cylinder and/or oil starvation. Yes, the middle of the piston tops usually looked good, leaving just the edges smashed all up.

What does the cylinder look like? How much scoring?

[turbo minivan]

ouch man! hey, al teast they didnt bust off a chunk of ring land and send it on a vacation in the cylender and valves! ive had 4 stockers do that to me...
detonation you say?!! =)

[puppet]

Look like they got pretty hot to me.

[Dohc Rocks]

Sorry to thread jack here but what you see on those pistons is not scuffing per se.....

Those pistons got hot and were starting to melt. I (also Canadian) have a set of 4 Wiseco's here in front of me that are the sme but much worse. I leaned out on a cool day in October and it just went lean enough to get hot... not detonate.

I can upload pics if you like.... they are out of a 98 Neon with a T3/T04B 2.4 swapped in running 18 psi boost.

[Joryn]

Posting some pics would be great. ARe you still using those pistons then? And if so what did you do to them before putting them back in (if anything).

Thanks
Joe

[slasky]

Quote:

Originally Posted by Chris W Hey Joe, Just spotted this thread. I will see about getting you another set of pistons at no cost. We might want to go to .040 over though. We have these in stock so there's no waiting. Give me a call. Chris-TU

Now that is customer service.