Blowby-too much smoke!

[Zed Head]

I think that it would be fair and appropriate to contact Datsun Spirit and see what they say.  Post #13 says that he built the short block.  Finding rings in the pan means that the piston must have broken all the way up to the ring lands.  That's a big deal.

#5 and 6 are the detonation cylinders though.  A perfect engine with a bad tune will still detonate and break things.  One tank of low octane a hot day and some hills could do it also.  But at least confirm that you didn't get scammed with paperwork for a different short block.  Could be that Datsun Spirit did not actually build that engine.

Just trying to be fair overall.  If this was a California Datsun engine we'd be tearing in to Al right now.

 

[zmanoside]

I don't know if you are saying that by me unplugging the pcv made the problem worse or better? I already contacted datsun spirit and Mr. Hosomi called me back and left a message. He said that he did in fact build the block for the car. He also stated that the previous owner had since had changed the head out on it. The block was built by Mr. Hosomi out of datsun Spirit. The head was built by Z-car source of Artizona. I tried to call Mr. Hosomi again just now to tell him the findings of the pistons but I didn't get an answer so I left a message. I don't anticipate any compensation from anyone, just info would be good....

[Zed Head]

4 minutes ago, zmanoside said:

He also stated that the previous owner had since had changed the head out on it.

There's your problem, maybe.  Better have that head checked.  Check combustion chamber volume.  Calculate compression ratio.  ID the cam profiles.

Surprising that the PO would change the head at 5,383 miles.  He was either trying to hop it up, or he damaged something.  Looks like you have some good parts but you should probably make sure that all of them will work well together.

[zmanoside]

The block and head combo is the stock configuration for a L28 out of a 1983 280zx....Im going back and forth with the previous owner now to see what would cause such catostrphic failure...

[zmanoside]

Would a carburetor tune cause this to happen?? Will the carbs need to be tuned again after the piston replacement??

[Zed Head]

1 minute ago, zmanoside said:

The block and head combo is the stock configuration for a L28 out of a 1983 280zx....Im going back and forth with the previous owner now to see what would cause such catostrphic failure...

The ID numbers are but the parts themselves may not be to spec.  The head was probably skimmed, raising the compression ratio, for example.  You have a custom engine now, F54, P79, etc. are irrelevant.

[zmanoside]

Understood. I will have the mechanic make sure everything is in spec before ordering anything. I don't want to slap new Pistons in it just to have the same thing happen due to too high of compression or something. I don't want this to happen again. This isn't even the engine I want in this car!! The more money I spend on this the more money I'm not saving for the RB25 I want to put in it. I need this engine to run well for the next year while I'm saving and building the rb25 to go in

[siteunseen]

A shaved p79 on top of a flat top pistons f54 is a good build. A member on here has about five of them! They also cam from datsun spirit. Elji? No detonation problems on his with SUs.

I can't understand how the skirts got broken though. The pistons taper down toward the skirts. Maybe they're ITMs and not OE Nissan? Cast vs. forged maybe? At any rate you need to find the cause or history will repeat.

[Zed Head]

Detonation breaks the ring lands, and the edges of the pistons.  Powerful explosions on the tops of the pistons.  Once you get a fracture it can propagate.

I have a vision of somebody not realizing what that engine noise was and just driving and driving with timing mis-set or low octane fuel.  Basically beating the heck out of the piston tops.  I filled my 1969 GTO with low octane and it was torture putting around at part-throttle waiting for the needle to get close to E.  Should have siphoned it out.  I had the intelligence of a high-school kid though.

Could be that over-heating was involved.  That might warp the head and blow the head gasket, which would explain the new head.  It might have had damaged pistons when the new head was installed.

[zmanoside]

Well so the mechanic called back. I discussed with him about making sure things were in spec and he pretty much said the head looks to be in flawless shape and he doesn't think anything above could have caused what he found. He said in his opinion it was one of two things: improper break in, someone hot roded it shortly after install or it was cheap cheap Pistons that were used. I dunno. I just told him to get er done. For everything it's gonna cost me a g to have her back on the road with new pistons. If she breaks again the engine will be ripped out with force and thrown in the dumpster to make way for the RB power plant 

 

Also, wanted to add, I just spoke with Eiji Hosomi from Datsun Spirit. What a stand up guy. In no way was I looking for compensation on his part for any of this, but he still offered to send a complete set of used "but in really good shape" pistons and rods for free for me to use in the process. He had no idea why this happened, he was actually speechless. He said this is unheard of. So, all I can do is wish for the best. 

Edited April 27, 2016 by zmanoside

[rcb280z]

I got first dibs if you are going to throw it away . 

Seriously, hope you get her fixed and fixed right. You'll probably really like the set up once she's running right.

[siteunseen]

Dumpster diving was how I met my first wife.