Buyer beware...(surplus pistons)

[dieseldummy]

Exactly one year and one month ago I repowered my '93 with a 6.2 shortblock covered in 6.5 gear. The 6.2 was punched out .020" and fitted with Ebay military surplus pistons... I just tore the motor out tonight since it wouldn't fire on one cylinder and was puffing out blowby something terrible...

Sure enough there was a cracked piston... I suspsect that they are Silvolite junk since there are no markings on them and they look similar to a Silvolite. They appear to start cracking in the wrist pin bores and go up and across the crown. There are some shallow surface cracks that appear to be heat related. They are in the ricardo recess where the casting isn't very finished.

The red outlines are of the main crack and some surface heat cracks. The blue outlines are from a tragic glow plug incident. The yellow is where material would be on a Mahle or stock piston.

I'm going to weigh the junk pistons and compare weight to a stock piston. Holding them side by side the .020" feels lighter than the stock bore piston. Overall these pistons are of poorer quality than the stock Bohn, Zollner, or aftermarket Mahle. The unmachined parts of the casting are very porus. The wrist pin bores are about 2 MM thinner than the above mentioned pistons and seem to be made out of an inferior alloy. I could understand the cracks being a result of the glow plug inhalation, but the worst cracked one has the least amount of GP damage. Ironicly the piston with the most GP damage (pictured) only has the surface cracks and the start of the wrist pin bore cracks. Luckily the block is ok. Buyer beware of surplus pistons...

http://www.thedieselpageforums.com/photopost/data/500/close_up_gp_damage.JPG

http://www.thedieselpageforums.com/photopost/data/500/close_up_crack.JPG

http://www.thedieselpageforums.com/photopost/data/500/medium/close_up_ricardo_cup.JPG

http://www.thedieselpageforums.com/photopost/data/500/medium/close_up_gp_damage_ricardo_cup.JPG

http://www.thedieselpageforums.com/photopost/data/500/close_up_underside.JPG

[Robyn]

I used Mahle in the last one I built from scratch.
The pistons I found in my 94 6.5 had the black hard coat on the top of them.
I am assuming this to be a ceramic of some kind. It came from the factory what ever it was.

[john8662]

Thanks for the pictures Justin!

I also wanted to thank you for reminding me to login to Oilburners.net to see the pics. :D

One tip tho, the photo album here allows you to upload any size image, you can then link them in your thread, here for example.

You make victim number two that I know about here. Another member reported similar issues with pistons marked Silvolite, and having them crack under turbo boost.

They were "shiny" and have a polished appearance to them? I'll bet they were Silvolites, in Clevite Boxes?

The only aftermarket pistons I know about for the 6.2 (6.5 maybe more) is..

Mahle
Sealed Power (Fed Mogul)
Bohn
Zollner
Silvolite

So, is it safe to say that you'd recommend steering clear of Silvolite pistons entirely?

I'd say so, kind of like my impresson of Total Seal gapless ring sets (cough, junk).

J

[dieseldummy]

I uploaded to the photo album and edited the origional post to get the pictured in. Leave it to John to point out that I'm being lazy...

I've had serveral sets of Mahle, stock pistons and a set of Zollners take some serious abuse and show no signs of failing in this manner. I origionally thought that the damage was a result of the GP failure, but like mentioned origionally the worst crack had minimal GP damage. I've got a set of Zollners with some serious valve dings and they didn't crack!

Most new stock pistons are have an anodized coating to help reject heat. Some aftermarket stuff is ceramic coated, but that's usually done after the pistons have been milled to lower compression thereby removing the anodized coating. When dealing with NOS parts (like I did here) the N/A pistons had no coating and the turbo pistons were anodized.

Ha ha, good old Total seal gapless huh John? Lets hear how you really feel about those...:eek: I'd say it's safe to say I won't be using the el-cheapo ebay silvolites again... I would strongly urge all members here to steer clear of them too.

I'm have a suspision that the spare short block is equiped with Sealed power pistons. It's punced out .040" and is in good shape, so if they check out ok there will be compression lowering tactics and coating involved...

[arveetek]

Just FYI, the pistons that the Diesel Depot machined for me were Mahle pistons in a Clevite box. They shaved the tops to lower the compression and then ceramic-coated them.

Casey

[dieseldummy]

More pics and update:

The first pic is a side by side view of a Silvolite and an OEM (Bohn or Zollner) side by side. The second is a crown shot of a Sealed Power(?) out of my spare short block. The third is a pic of an 18:1 Zollner side by side with the sealed power. 4th is a Sealed power by the Silvolite. 5th is a pic of the underside of the 18:1 Zollner.

So far the Sealed Power pistons seem to be the beefiest and best built. The Silvolite are the cheapest. There is a definate difference in the alloys used between the Silvolite and the rest. I threw out all of my old Mahle stuff so I don't have any of them to compare to.

I did some measuring of the compression heights, wrist pin bore thickness 2 ways and skirt thickness.

Silvolite ? Zollner ? Stock 6.2 Sealed Power ?
Wrist pin boss front to back 1 1.06 1.07 1.19
Compression height 1.505 1.47 1.505 1.495
skirt thickness 0.21 0.145 0.15 0.21
Wrist pin boss side to side 1.61 1.645 1.635 1.685

The sealed power pistons that I'm going to use from the spare short block are already .010" shorter so I'll only have to take off .020" or so to get my desired compression ration. Should be interesting this time...

http://www.thedieselpageforums.com/photopost/data/500/medium/oem_side_by_side_silvolite.JPG

http://www.thedieselpageforums.com/photopost/data/500/sealed_power_crown.JPG

http://www.thedieselpageforums.com/photopost/data/500/medium/zollner_side_by_side_sealed_power.JPG

http://www.thedieselpageforums.com/photopost/data/500/medium/sp_vs_silvolite.JPG

http://www.thedieselpageforums.com/photopost/data/500/zollner_underside.JPG

[john8662]

Nice pics.

It's interesting to see the different designs for the pistons between mfg's.

They all vary somewhat, mainly in the support of the wrist pin itself.

I guess Silvolite lost that battle, most likely due to the alloy content of the piston and placement of the casting in necessary places.

Another interesting tid-bit to add to this testing is that 6.2 pistons are typically un-coated, so a good coating of Ceramic etc. would be necessary for turbo use. Ain't there a Holset on there?

J:eek:

[85-m1028]

I would add myself too, the engine I pulled out of my CUCV "not the original because the valve covers were stamped with 87 and mine an 85" had several cracked pistons!!

[dieseldummy]

I would say that the Silvolites were a bad idea for Clevite to box up in their own boxes... I see a set similar to the ones I have can be had for $98 on ebay...

Not to argue with the ceramic coating thing, but ceramic or anodizing aren't used in alot of turbo diesel motors... One thing is for sure the new motor will have coatings in it!

85-m1028 I'd say it sounds like you've been had by some crapy pistons too! Hopefully you replaced them with something better.

[85-m1028]

I got a hmmwv take out engine in the in my truck right now. The cracked piston block is in the garage "slated for a rebuild" the heads looked great and every thing else bottom end wise did too!!

[5.7L diesel]

I'd say so, kind of like my impresson of Total Seal gapless ring sets (cough, junk).

I installed one of those piston ring sets in my newly rebuilt 1981 5.7L diesel in August of this year.I had it punched .030 oversize using new seal powered pistons with new gapless rings from total seal.The engine behaves beautifully.It runs super smooth and i'm well pleased with it.It pulls extremely well on any grade.

Those ring sets are great in my opinion.I certainly can't say anything negative about them.

John,what kind of problems have you experienced with this ring set?

[ronniejoe]

I'm running them in my engine as well. Seem to be working very well.

[john8662]

John,what kind of problems have you experienced with this ring set?

I'm gathering up my data to make a little article I'll place here in the forum to explain.

Been pretty busy.

In short. I bought a ring "set" not just the 2nd compression ring. These were NOT converted Mahle rings as RJ had either.

The quality of the gapless ring was good (although it was file-to-fit), the other rings on the other hand were poor. Wide range of gap between rings (it was the ring not the bore) and questionable quality of the oil control rings, and one was chipped already (before being run).

I tossed them, after speaking to a not-so-wonderfull tech rep at Total seal. TS refused to replace any of the parts, and said the ring gaps were all in spec "according to the industry" and that the ring gaps specified by GM in the BOOK were WRONG, because there was no possible way to run an engine with that (according to him) little gap (2nd compression ring). Well, they did offer to replace them, as a whole set, but I'd already filed the 2nd compression rings to get a (waaaaay better gap range than they could ever dream of), and I'd have to send them back too. Then he backtracked and said that since I'd filed them that I couldn't send them back. Here is what is really funny, this is the SAME guy I talked to on the phone that told me they were file-to-fit in the first place BEFORE I filed them that I'd HAVE to "open it up a bit"..

Oh this is getting me stewed all over again.

more later...

J

[grape]

the only gapless stuff i've seen isn't street friendly.........eats cylinder walls in a hurry, they were all the low tension dry sump stuff as well.

[dieseldummy]

I was always under the impression that Gapples rings were ok if you set the endgap up proper...

Back on topic I browesed Ebay this evening and noticed that the same seller I got my pistons from is selling single lots of 6.2 Silvolites... Others are selling Clevite boxed silvolites claiming that the buyer may get either Silvolite or Mahle... It's not just 6.2/6.5 pistons either, I've seen 6.9/7.3 IH stuff too.

[beast]

i have used total seal rings in a number of Harleys with great success. it could be they have changed owners or managment. it would be worth contacting them and trying to find out what happend. the drag racers have been using the for years, almost 0% blowby!

[84 Convert]

I just tore down the engine in my K30 due to the fact that the dipstick would not stay in the tube. Turns out that the piston was cracked and resembles the pics if the Silvolites shown earlier in this thread. The crack begins in one pin boss up under the crown and back to the pin boss on the other side. It is cracked through to the top at least 3/4 of the way across.

I was bad when I put this one together...all used pistons mixed and matched best of three sets. I know this one was thelowest mileage of all but cracked before anything else. All the other pistons are good.

Moral of the story... you can scrounge but don't get the poor quality stuff.

Gregg