Motor mystery.... please help.

[blown383z28]

Hey guys
im looking for some help. I had a motor built last year for my 93 m6 camaro. Ill try to keep this as short as I can. Quick rundown on the car.
93 z28 camaro,
rear mount turbo set up (with front mount intercooler, about 8-9 psi)
tuned on pump gas 93
motor is a stroked 377, compression about 10.3-1
CNC ported stock heads and intake
No egr, or emissions to worry about
2 colder heat range plugs
ECM converted over to ob2 24x with cam sensor and 24 reluctor wheel, 8 coil set up just like GM LS1
has your pistons with coated skirts and ceramic coated tops (part # on piston is 102521)
rings are Total seal for boost, steel top, napier 2nd
car was dyno tuned for afr at 11.1-11.3

Problem I have is from the second I started the motor in the car it had more blow by than it should have (ive had a lot of other motors rebuilt by same builder). Ran a few heat cycles through it and changed oil (Rotella T non synthetic 10-30, 15/40 was put in b4 any high rpm or dyno time). Let car warm up and put a few miles on the car. Another thing I noticed was blue smoke on deceleration (under vacuum). I called engine builder and he wants sure. Said to put some more miles on motor to see if rings seat better.
After that, loaded up on trailer and took to dyno and got drivability and WOT tuning finished. Put a few thousand miles on the car and oil under vacuum never got better. I then replaced valve seals and intake gaskets twice to make sure it wasn’t that. No change at all. I also removed turbo from the intake and no change (no oil coming from turbo and intake pipes where clean).
Right at the end of last summer I was out racing a guy and did 4 pulls with him. 40-140 mph. Air fuel always looked good and have NEVER heard any knock nor seen any on the dyno with laptop. After the 4th pull I notice something wasn’t right and now it smoked under acceleration (blue). I have now removed the motor a tore it down to find about 5 bad pistons. One is melted/broken and, the other 4 are pitted bad (detonation) and the top ¼” of piston is starting to lift up. The rings have micro welding on them also. The pitting is in the same spots on all the pistons, on the outs side of the intake valve relief. Do you have any idea what’s going on here? Again AFR was always good and never “heard” any knock.
http://i1215.photobucket.com/albums/cc518/blown383z28/IMG_20141229_145002_131_zpsec512c59.jpg (http://s1215.photobucket.com/user/blown383z28/media/IMG_20141229_145002_131_zpsec512c59.jpg.html)
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http://i1215.photobucket.com/albums/cc518/blown383z28/IMG_20150106_074003_416_zpsc3c9a92c.jpg (http://s1215.photobucket.com/user/blown383z28/media/IMG_20150106_074003_416_zpsc3c9a92c.jpg.html)
http://i1215.photobucket.com/albums/cc518/blown383z28/IMG_20150106_073801_813_zps08586ce9.jpg (http://s1215.photobucket.com/user/blown383z28/media/IMG_20150106_073801_813_zps08586ce9.jpg.html)
http://i1215.photobucket.com/albums/cc518/blown383z28/IMG_20150106_073741_860_zps378c8cac.jpg (http://s1215.photobucket.com/user/blown383z28/media/IMG_20150106_073741_860_zps378c8cac.jpg.html)
http://i1215.photobucket.com/albums/cc518/blown383z28/IMG_20141229_152509_614_zpscb0e91bf.jpg (http://s1215.photobucket.com/user/blown383z28/media/IMG_20141229_152509_614_zpscb0e91bf.jpg.html)
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http://i1215.photobucket.com/albums/cc518/blown383z28/IMG_20141229_151259_071_zps7e302f87.jpg (http://s1215.photobucket.com/user/blown383z28/media/IMG_20141229_151259_071_zps7e302f87.jpg.html)

[SS RRR]

Something is definitely up with your AFR. That's textbook detonation. Tuning issues is my guess.

[GuillaumeC]

TR6 plug is wrong for that application, but I don't think that could cause your problems on its own.
I'm with SS RRR, that's detonation.

What was your AFR in boost? timing advance in boost?

[BALLSS]

what size rods?

can't se all the pics but looks like side loading. rings never sealed is a guess as a result

[blown383z28]

hey guys, thanks for the replies. WOT AFR was around 11.2-11.4. I haven’t looked at the tune yet to see what the table is at. The guy that tuned it has tuned a lot of my other cars and been doing it for years ( I know years still don’t mean much but). I never really had a problem with any other cars with him.
for plugs I thought they were TR55’s id have to look for sure at the shop. I thought when I looked them up while back it was 2 steps colder. What plug would u have used?

I agree 100% it was detonation. Ive had a few guys say wit it burning oil the oil was also killing octane and the oil deposits where making hot spots also. I have a pic of the broken piston b4 everything was washed. u can see all the oil on them. had someone also mention a bad burn pattern on the piston. after we cleaned them it does look like it was pretty lean on the side the pistons are all beat up from.



http://i1215.photobucket.com/albums/cc518/blown383z28/IMG_20141229_123318_552_zpsfc1b49d3.jpg (http://s1215.photobucket.com/user/blown383z28/media/IMG_20141229_123318_552_zpsfc1b49d3.jpg.html)