maybemark Posted February 16, 2012 Share Posted February 16, 2012 I have an 82 280 zx turbo, which i tore the engine apart. My head was good, cleaned and rebuilt. I was told by the machine shop, that my pistons are bad, because i have too much lateral play in the slot with the ring. # of my cylinders show oil on the exahst side. I read that the limit should be .1 mm of playbetween ring and top of slot. I take out the ring and it shows wear. How do i know if my piston slot is worn, or the ring is worn? Does anyone have data on the thickness of the stock ring, or dimentions of the slot for the top ring? When I look at my bore, it looks great, and the machine shop said it would be ok, if i don't race the car. i have intentions of racing on the 1/4 mile track and street car. The macnhine shop says get over sized pistons and rings, and re-bore and hone. I would like to get other feed back if possible Thanks Mark Quote Link to comment Share on other sites More sharing options...
BrandenZ Posted February 16, 2012 Share Posted February 16, 2012 Refer to my thread here in a similar subject (re-ringing the motor due to burning oil): http://forums.hybridz.org/index.php/topic/104074-burning-oil-in-2-looking-for-suggestions-as-to-why/ I haven't had a chance to fully seat the rings yet to completely say with confidence that it's working, I'm fairly certain it will run great once I solve one last issue if the initial crank is any indicator. I personally did not bore the block or get over-sized pistons. There was very little ridging, so I didn't feel inclined to use a ridge-reamer, but the cross-hatching was gone in all cylinders, so I did re-honed it. One thing in theory that you could do is buy just 1 ring set (as opposed to the entire set for 6 cylinders), then install the top compression ring inside each of your cylinders and measure the gap. I was able to do this quite simply by compressing the ring with my hand, pushing it into the cylinder, then turning a piston upside-down to apply even pressure across the ring, and moving it down below the top-ride (the area where it will actually ride when installed on the piston), and measuring it with a set of digital calipers. Unfortunately I don't have the spec I used off-hand. All of mine came out perfectly in-spec with the new rings, so I kind of put it out of my mind. However, you can download the factory service manual and look it up yourself here: http://www.xenons130.com/reference.html I would suspect that if your rings are old and worn, that the old ones will show out of spec. To me the more important test would be if a new set of rings showed in-spec. If not, then likely you will have to go the route the machine shop mentioned. PS -- Don't forget new rod bolts (Tony mentioned this in my thread), very important as the stockers are torque-to-yield. Quote Link to comment Share on other sites More sharing options...
maybemark Posted February 17, 2012 Author Share Posted February 17, 2012 thanks for your reply 1st, i do have a service manual, and it does not show anywhere the thickness of the ring, or slot on the piston. It does show the lateral play max. plus it shows the max. gap of the ring, when in the bore. this doesn't help me though, cause I don't know what the ring size should be, or, the slot size. I looked everywhere in the manual. My bore looks great, still has the cross hatches showing. i haven't read the link you sent me, and i thank you for sending it to me, and I will check it out after dinner. thanks again Mark Quote Link to comment Share on other sites More sharing options...
maybemark Posted February 17, 2012 Author Share Posted February 17, 2012 i did get a chance to read all of your link you sent me, thank you. I am afraid my problem is different. All my rings have movement, maybe too much movement, like the machine shop says. i pulled a couple of the top rings off, and i can see that there is wear on the ring, but i still don't know if the race, the ring rides in is too wide. I wish i would know the specs on the size it should be. thanks again, Mark oh, by the way, i found a great place to purchase parts online called northern auto parts, great prices and they carry ITM rings and pistons and felpro gaskets, well many things Quote Link to comment Share on other sites More sharing options...
NewZed Posted February 17, 2012 Share Posted February 17, 2012 Sounds like you just need the thickness of a known-good ring. Preferably a new one. Then you can do the math on your parts. Maybe someone will measure one for you. Quote Link to comment Share on other sites More sharing options...
maybemark Posted February 17, 2012 Author Share Posted February 17, 2012 yes, this is all i need, the measurment of a new ring and or the measurement of a new piston race for the ring thanks Quote Link to comment Share on other sites More sharing options...
BrandenZ Posted February 17, 2012 Share Posted February 17, 2012 I'm definitely not an authority of any type regarding motor rebuilds, but just from my most recent experience, it seems to me like you should be fine without a re-bore and just a new set of rings. In my case, the fact that the cross-hatching was gone is an actual indicator that of wear inside of the bore of the block, and yet I was able to re-hone and apply new rings that were in spec without any issue apparent as of yet. I'd say the fact that you see cross-hatching is a good sign. I'd also expect that rings themselves to wear as opposed to the ring lands on the pistons themselves, especially given the fact that supposedly ours all came with moly top rings from the factory. I believe the oil control ring set is cast, so if there's any wear to be found regarding the depth of the ring land, I suspect you'd find it there. Unfortunately if you posted this a week ago I could provide actual depth measurements that I experienced on my pistons, and ring-width for a new set, but mine's already buttoned back up and I hope to keep it that way for a long time to come! Also please do take note if you go through northern to ensure that you have the right set specific to your model. 280zx ring sets are different than all S30s, and they're also different between the turbo and N/A version. Additionally I found that most do stock the correct set, but it's chrome (which you don't want) as opposed to cast or moly+cast. There was someone selling a set of F54 pistons recently in the classifieds. Perhaps you could find that post and, if they haven't sold them yet, see if they'd be kind enough to measure the depth of all 3 ring-lands. Outside of that, maybe Tony D or John C will chime in here and provide more statements of fact as opposed to the theoretics that I'm spewing. Quote Link to comment Share on other sites More sharing options...
maybemark Posted February 18, 2012 Author Share Posted February 18, 2012 Thanks for all your help and input. I ended up calling northern auto, and they were able to supply me with the dimensions of the ring lands, I put several feeler gauges together and put them in the lands, and yep, i am very close with the ring lands. (.02)difference i am not going to replace the pistons, just get a new set of standard rings Also, the machine shop suggested to re-bore because i have a slight taper in my bore, he said, if i am not going to race, i can get away with just a hone. I plan to do 1/4 mile runs, besides my everyday car. I am wondering if this machine shop is just looking for more work for him, and more money from me. What does it take to hone the bores? Do i need to pick up a special tool, or can it be borrowed from your local auto zone? Also, in this post it was suggested to install new rod bolts. I've been told by someone else these engines don't need new ones. Which is right? It has also been suggested to replace the main bearings and the rod bearings. More feedback is much appreciated thanks all Mark Quote Link to comment Share on other sites More sharing options...
BrandenZ Posted February 19, 2012 Share Posted February 19, 2012 Check out this link, exceptional write-up on the majority of what you're looking to do: http://datsunzgarage.com/rebuild/ I picked up the same hone he recommends on the page, bought the exact part number referenced, and got the finest grit they made. Turned out great in my case, all done with just a simple cordless drill! You should super install new rod bolts, particularly if you intend to daily drive it for a long period of time. The factory bolts are stretch-to-yield, basically this means that when they're torqued to spec, the actual bolt stretches and conforms to lock into place. They're never meant to be re-used, as if you attempt to re-torque them to spec, they'll stretch again, weakening the strength of the fastener. I found a set on ebay for I think $60. A lot cheaper than repairing a piston through the block if you re-use them and they end up snapping. From what I've read, main bearings seem to rarely be of any issue. In general the answer is always yes, since you're already 90% of the way there in terms of the work involved, but I personally didn't bother. I checked the spec of one of the mains with plasti-gauge (the main bearing I had to pop out to replace the rear main seal -- which I do recommend doing while you're there) and it came out to spec, so I left them all alone. I did go ahead and replace the rod bearings. You've gotta take the rodcaps off anyway, and they're relatively cheap as a set -- very cheap insurance in my book. Personally, I did: New rings, new rod bearings, new rod bolts, new rear main seal, new oil pan gasket, new front cover seal, new head gasket, and new intake/exhaust manifold gasket. Ran it hard just today, still slowing dialing the timing back up -- zero smoke, plugs read perfect, 160+ compression across the board -- Very pleased! Quote Link to comment Share on other sites More sharing options...
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