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

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

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...

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....

Got a call this morning bright and early. Rings from #6 were broken and in oil pan. #6 piston has a cracked skirt. #5 piston skirt is also cracked with damaged, but still in place rings. Mechanic called to ask if he could proceed to remove the rest of the pistons to inspect the remaining pistons and cylinders. Obviously I said yes. He said the #6 cylinder didn't actually look too bad, and will most likely be fine with a good honing, and the rods and bearings looked good too. So I think at this point its looking like a new set of pistons and rings. Hopefully all of the cylinders will be good with just a hone....

Dropped the car off this afternoon. Had a bunch of Zcars in the mix in the garage! Also, spoke with Les Cannaday out of Classic Datsun Motorsports about the car before I took it down. He knew of Buck and the shop I was taking it to and said he does great work. I am confident she is in good hands! Fingers crossed for cylinder 6's good fortune!!

South Bay Datsun Repair in Chula Vista. I ran it by the Z Club of San Diego and he said they have members that go there and like it. The owner and I talked for a good 15 min on the phone, I explained everything to him.

Hey guys sorry for the lack of update. i just had some minor surgery yesterday so I will be out for a couple weeks. So, I know I know I was all moto to take care of this piston ring problem myself but at this point in time I really just want to have the car back on the road. I called a reputable Datsun shop here in San Diego and got a very good quote to get this done. If I feel up to it I will get the car to him on Tuesday next week and have it back by Friday. If I did it myself I wouldn't even be able to start working on it for weeks and weeks (no lifting or strenuous activity from the surgery). I did get the book mentioned and will start going through it soon. I'm really just wanting to drive the damn car at this point. I'll let you guys know what he finds in there. Hopefully no cylinder damage. --Z

Oh, I forgot to mention. On 2 of the adjustments I had to removed the rocker spring to get at a better angle to be able to loosen the adjustment nut. Hopefully this is ok. I just reinstalled them after I was done. I think they are known as mousetrap springs? Anyways they went back on no problem. I didn't ready anything about having to remove these to adjust so I was a little hesitant but did it anyways ha!

Well, she started much easier and she idles much better. Still smokes like a sob and the compression on 6 is still at 90. Gotta work tonight and tomorrow night so she will sit for a couple days...

Good morning! Well, exhaust valve lash was tight. I could not get the .008 feeler in there at all. I didn't try anything smaller. Tonight I'm going to try and do my first valve adjustment, put everything back together and drive it. See how she runs for a little bit and then do another compression check after I drive it real good as zed head suggested. I bought what I needed to build a crankcase evacuation system that will route the extra blowby out of the exhaust. I'm thinking/hoping that the ring isn't seated due to not having any sort of vacuum from the crankcase and the pcv was capped and that uncapping the pcv and installing the evacuation kit might help seat a ring. It may work it may not. My friend has a bore scope and we will take a look in there and see what we can see. One of the reasons I bought the car was to have fun and wrench on it myself, so that's what I'm gonna do. I'll get the books on Amazon and use my friend and his tools when I get to that "defeated" point. I really appreciate all the help and motivation. I've been browsing Z forums for a while, there is a reason I joined this one. I work A LOT and have two small kids that are a lot of work right now (they need their own valve adjustments) I will keep you all updated on any progress. Cheers. Zach

What I've gathered is some stuff called bon ami or magic mystery oil, squirt it down into your cylinder, let it sit overnight and it can help free up a a stuck ring and helps rings seat properly.

Hey my bad, I didn't see that you had said that it looked like there was a chip in the lobe. I could have told you guys it was a reflection. Just got a text from the previous owner. Chrome rings were used in the build. I had a guy at the auto parts store next to me mention piston soaking. Worth a try? Or a no no.

All of the lobes look to be pristine to me. Nice and uniform shape and shiny. That is just exactly right, it is a reflection of the circular casting mark right above

Well adjustment is out of the exhaust valve on #6 however with my 17mm wrench I just can't get a good enough bite on it to turn it, too thick of a wrench. I'm beat. Going to get some sleep, regroup and think about what my plan is going to be. I'm tempted just to throw the damn thing back together and bring it to my friend that knows what he's doing and has the right tools. I'm confident he could pull this engine in less than an hour. It would take me all damn day. Good night fellas thanks for your help. I'll keep you updated. And yes, I verified both times I rried to turn using the camshaft bolt the tranny was in neutral

Thanks. I wasn't able to get my tools in there to reach the crankshaft bolt to turn it. I put it in 4th and rolled it back and forth and that worked. Now am I able to just adjust the lash on just the 6th cylinder or do I have to do all of them?

I don't even have a 24 or 27 and I'll have to get a socket that is long enough to reach in there. Curious, how is it that in both of the videos I watched they are using the camshaft bolt to turn it with ease?

Pics of the last lobe on the camshaft. I'm not sure how I'm going to get to that crankshaft pulley bolt that I'm pointing at without removing that stuff down there. What size is the bolt on there?

Ok so I guess I'm doing it wrong. Both of the videos I watched they were using the camshaft bolt. So in order to use the crank bolt I need to disconnect the fan and all the other crap down there?

This is what I am trying to turn. Is this not right??

That's exactly what I did my friend. Tranny in neutral, all plugs out using the main bolt on the camshaft that has the timing chain directly on top of it turning clockwise if you are looking to the rear of the car. Won't turn. I just tried again and almost pulled a hammy. Won't turn one bit.

Ok so I have the valve cover off. Went to turn the cam and it doesn't move. At all. All of the plugs are removed. It just feels locked up. I used as much strength as I could and it did not move. Am I supposed to loosen something else to be able to turn it?? I'm watching 2 YouTube videos on valve adjustments on L series motors and they don't mention loosening anything. Luckily the heel of the exhaust lobe on the cam on 6 is pointed up, where it should be to check correct? I don't expect a reply cause it's 250 am and you are all sleeping! Damn night shift! from what I've read after posting this is either a broken valve or rod or perhaps there is a piece of the ring in the cylinder that is preventing the piston to move? But how is this possible if the car ran fine??

Ok cool. That makes me feel better about taking it off. I dint want to take it off and wait for another gasket to arrive so I can bring it to my friend. I'll take it off tonight and read up on how to adjust. I hope so too. That would be awesome but from everything I've read all I keep hearing in my head is ring ring ring.

I just texted the previous owner for more info and he gave me Mr. Hosomi's cell number. I called him and left a message. I started taking everything off and was about to remove the valve cover and thought twice about it. I'll have to put a new gasket on if I take it off right? I would rather have my friend take a look at it first and wait to hear back from the builder before I open it up and start doing anything.