Hey everyone,

Forgive me if I'm not following forum protocol, this is my first post and I'm a little technologically impaired.

I had a couple questions regarding precups. I noticed there are a few posts in the forum about this topic already, but most of them are from quite a few years back and it seems harder and harder to find replacements these days. I'm in the process of rebuilding a fairly low-mileage (80,000) '83 MY 6.2. Upon teardown I discovered in a couple cylinders it seems as though something broke off and went for a ride. The tops of two of the pistons were a bit hammered, nothing catastrophic, but enough to warrant a new set of pistons. The cylinder walls also showed some vertical scoring that required boring out to 0.030 over. The corresponding combustion chambers in the head showed similar signs of wear as pictured. The heads themselves are in good condition (crack free as far as I can tell, and flatness checks out within spec), but the two precups are pretty beaten up. I was wondering what would cause damage like this - Possibly part of a glow plug breaking off? I just want to make sure I address it at the root cause before it all goes back together. My other question was if the damage pictured warrants precup replacement? I have read in the manual that any cracks over 5mm require replacement. Most of the precups are cracked, about 6 out of 8 of them, and though some extend just over 5mm, none are too close to the head gasket sealing bead. From my research on the forum this is pretty commonplace, and I would probably feel comfortable running them as is, if it weren't for the other damage pictured. My last question, if precup replacement IS recommended, is where to source these damn things? I have heard conflicting reports on the quality of eBay precups, specifically imported parts. There's one eBay seller that seems legit as far as I can tell, but I really have to just take his word on it. They are listed as 6.5 precups, but I believe I read somewhere that they are all interchangeable but the size of the chamber on the diamond cups is larger and may reduce fuel economy. I will add that I will be installing a Banks turbo kit to the engine, and if the larger cups will be beneficial to performance or longevity, I'm not opposed to a slight drop in MPG. I've also heard of another user getting some through PTC Power. This site has the correct part number listed for the stock 6.2 3 notch cups. Unfortunately I was unable to get ahold of them and inquire about prices or part sourcing. I will post both links below. Does anyone have any experience with either of these sellers? This is my first diesel rebuild and though I feel fairly comfortable, I'm still in somewhat uncharted territory. I'm in the mindset of replacing anything within reason while I'm in it just FYI. This forum has been my best friend throughout this process, but until now I've just been a lurker. Any help would be greatly appreciated. Thank you in advance!

eBay Link
https://www.ebay.com/itm/6-5L-6-5-Di...-/163097660487

PTC Power
http://www.ptcpower.com/inventory/inventory_gmc.aspx

precup1.jpgprecup2.jpgprecup3.jpgpiston.jpg