Well, I just got my b16 block back from the machine shop, and one of my brand new CP pistons came back all scratched up. Is this acceptable? I can feel the scratches with my fingernail...

Here's the skirt:



A small ding on the dome:



And one of the other pistons without dings in the same light and position for comparison:

 

That's the kind of thing that doesn't matter, but it would INFURIATE me if some ****-stick did that to my pistons. Go back and start making demands.

As far as concerns, it won't affect anything. The cyl. walls and rings are what make the seal. That section happens to be a thrust surface, which is unfortunate, but as long as there are only depressions (no raised material) then it won't scratch your sleeves.

Still, I think that's unacceptable. I'm angry, and it's not even my piston/motor. I say go back and make some demands. Partial refund, free machine work, etc. If they tell you to buzz off, go back during the middle of the night with a molitov cocktail and burn that mother down.

EDIT:
Also, you'll probably want to rub down the "ding" with some fine grit sandpaper (600 grit should do) to smooth it out. Knife-sharpening stones also work great (my preference). The last thing you want on a piston face is a sharp point (potential hot-spot). It looks pretty insignificant in the pic though.

And feel free to post the name of the shop, so that we may **** all over them.


Modified by Legion at 2:17 PM 2/22/2008

 

Interesting... You see, I knew I needed to pick a machine shop carefully. I went with this one b/c a very close friend who's a mechanic recommended them. The guys been in business for a long time. I really should have known better though when I showed up and the shop was a mess. Lesson learned.

One thing that really bugs me about the scratches is that in Jeff Evans' engine build article, he says "you have to make sure that the pistons don't get scratched." He recommends always placing them on paper towels or the like. Any comments on this? I've sent an email to CP with photos to see what they say about it.

After this mess, I'm beginning to question if he did the bore/hone properly. I don't have a dial bore gauge, so I'm thinking about bringing it to another shop and having them check the bore as well as make sure that the guy bored the sleeves dead-center. Really, really, really annoying...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">
While the scratches are definitely unsightly, they will not hurt anything. Just make sure there is no material protruding up above the surface of the skirt. The skirt should still feel smooth if you glide the palm of your hand over it. The other picture I see a small divot on the top land, you can just lightly sand it down with some fine 400 grit sand paper. Makes sure to wash the pistons thoroughly before assembling.



Sincerely,



Darius Tarman

Sport Compact Sales/Tech Support

CP Pistons
</TD></TR></TABLE>


Modified by cobra2326 at 10:32 AM 2/22/2008

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by cobra2326 &raquo;</TD></TR><TR><TD CLASS="quote"> in Jeff Evans' engine build article, he says "you have to make sure that the pistons don't get scratched." He recommends always placing them on paper towels or the like. Any comments on this </TD></TR></TABLE>

Yeah, well nobody likes scratched pistons. He's just making sure you're careful because forged pistons are always so darn soft. I can only see it being an issue if it's in the sealing/ringland area. I used to have scratches/dings in all kinds of engine parts and I'd always get worried and run to Earl Laskey for advice. He pretty much told me the same thing every time - get a honing stone or 600 grit sandpaper and smooth the area out.

I've been doing that for years now, on everything from crank girdles to cam caps (even a crankshaft journal one time ). I've never once had a problem with any of these fixes.

And I know it sucks in the beginning when you have to sand down part of a piston top and ruin the pretty mirror polish, but you'll get over it. My pistons all have a 600 grit finish by now because every time I pull the head off I clean the carbon off the faces with sandpaper.

You should be pretty confident now, seeing as CP backed me up nearly word for word. Raised portions on the skirt are all I'd worry about.

 

Yeah, I really appreciate the help and good advice. Not something to take for granted.

Part of me wants to give the guy a piece of my mind, but I'm going to get all the facts and then talk to the guy. We'll see what the other machine shop says. I'm going to be standing there right next to them this time too. Once I get that, at the very least I'll call the first shop and let them know that this type of thing is really unacceptable from a professional business.

 

man dude I would have been pissed off, never go to those idiots again.