calpoly-z Posted July 2, 2012 Share Posted July 2, 2012 This weekend I had an opportunity to do a little work on 77 which has been sitting on stands for basically the last 3 years while I tried to find the time to upgrade a few items that have been on the to-do list for a long time. Anyway one such item was an Arizona Z-Car aluminum oil pan that I picked up used here a year or so ago. I had the car up in the air anyway so I decided to tackle this project since it was one of the last things I needed to do from under the car (By the way, installing this cast pan with the engine in the car is a major PITA. Highly recommend doing this with the engine out.) After the install, when I was cleaning the old pan out for storage I noticed a small piece (~1" in length) of broken piston ring sitting in the bottom of the pan. I rebuilt this engine about 6 or 7 years ago while a broke-ass college student so the rings were something I picked up at a local Parts Plus and I did the install myself. Entirely possible that I screwed something up. I have no idea how long this piece of oil ring has been sitting in the bottom of my pan, and the engine seems to run fairly decently (well it did about a year ago which was the last time I had running and took it for a quick spin around the block I'm). So now I'm curious if I should worry about this or just go ahead and leave the engine alone until something worse pops up? I did a quick compression check this afternoon and everything looks ok for the most part. (~120 +/- 5 PSI across the board) Cyl 3 & 5 spark plugs definitely showed signs of burning a little oil but all plugs had nice tan tips so at least my tune is pretty close . I'm trying to build a somewhat comfortable but still quick car that I can use as a mostly daily driver in the future, so I just installed a Vintage Air A/C system into the car and a 240sx trans. I'd like to stay with the L6 but if it becomes necessary to rebuild this engine again I may just pull it and try to get my hands on an SR20DET or similar turbo 4cyl to save some weight and get better fuel economy (best I was getting with the L28 is about 17/24 which ironically is about the same as the 370Z I'm currently driving) Your thoughts guys? Run it till it blows, or go ahead and start the engine swap process while I already have the car down and I'm not used to driving it anyway? Quote Link to comment Share on other sites More sharing options...
johnc Posted July 2, 2012 Share Posted July 2, 2012 The car has been on jackstands 3 years... what's another couple weeks to pull the pistons and fix the rings? Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted July 5, 2012 Share Posted July 5, 2012 I would pull the pan and look at the bottom of each piston. I would say about 20% of L28s I have opened have chunks of piston skirts in the pan. It's easy to see the bottoms when the pan is off. That piston ring part might have become wedged in the oil pan during or before your last build. Quote Link to comment Share on other sites More sharing options...
calpoly-z Posted July 13, 2012 Author Share Posted July 13, 2012 (edited) Well I've been mulling this one over for a bit and decided to just bite the bullet and pull out the motor. Hoping to get the motor out tomorrow and at least partially torn down to look for damage. I've never seen any other large metal shaving during oil changes so I'm not expecting any broken piston skirts. If I do find that though I'm seriously contemplating swapping my dished pistons out for some flat tops. I like the thought of a little more off boost response and I'm not planning on building a monster. 300whp sounds like plenty to me. I'd like to get my hands on an "A" cam or a mild turbo cam while I'm at it. And I will probably finally get my stock t3 sent off to be turned into a t3/t4. I'm sure there will be plenty other "while I'm at it" purchases as well. Which is a big part of why I didn't want to pull it in the first place. Oh well, no time like the present, right? Edited July 13, 2012 by calpoly-z Quote Link to comment Share on other sites More sharing options...
Lazeum Posted July 13, 2012 Share Posted July 13, 2012 (edited) I'm interested in the results from your observations. For your information, I purchased ITM flat tops pistons for $180. If your engine is out, cost is not something that should stop you upgrading those if you're looking for stock style pistons Edited July 13, 2012 by Lazeum Quote Link to comment Share on other sites More sharing options...
calpoly-z Posted July 15, 2012 Author Share Posted July 15, 2012 Where did you find pistons for $180? The ITM sets I'm finding include rings and are about $280-300 for a set. I got the engine out yesterday. Unfortunately I'm spending the weekend in Lubbock at a redneck wedding so I haven't had a chance to get the engine on a stand to begin tear down. I read about 3/4 of the cylinder Head cooling thread last night so now I'm planning on tapping the 5-6 cylinder coolant passages. I really want to see how an 8.5-1 turbo engine responds with these modifications. Seems like I should be able to get away with more than 14-17 deg advance at full load like recent posts have suggested. Quote Link to comment Share on other sites More sharing options...
Lazeum Posted July 15, 2012 Share Posted July 15, 2012 (edited) Where did you find pistons for $180? The ITM sets I'm finding include rings and are about $280-300 for a set. See the following link: www.clarksdiscount.com The owner has been great with me, I'm located in Europe. Parts were ordered on Monday, they were at home Friday morning. Emails were all answered within 24hrs & he's having tons of parts for our Z's at very decent prices. Edited July 15, 2012 by Lazeum Quote Link to comment Share on other sites More sharing options...
calpoly-z Posted July 15, 2012 Author Share Posted July 15, 2012 I will be sure to check them out. Much appreciated! Quote Link to comment Share on other sites More sharing options...
Lazeum Posted July 15, 2012 Share Posted July 15, 2012 you're welcome & I'm glad to help serious shops to do some business Quote Link to comment Share on other sites More sharing options...
calpoly-z Posted August 12, 2012 Author Share Posted August 12, 2012 Finally got around to tearing the short block apart and discovered the culprit. Cyl 3 lower oil control ring was pretty mangled up, destroying the piston and deeply grooving the bore wall. Definitely going to have to find a machine shop locally. I'm already bored .5mm over so hopefully it only needs another .5mm of bore to remove the grooves. I know +1mm pistons and rings are available, but I'm not sure thats going to be enough to take out some of these grooves. Anybody know what the largest oversized pistons that are available for a standard crank L28? Not sure what would cause this to happen. I assume I screwed up somehow when assembling this engine several years. Any idea what I did so that I can avoid this issue in the future? Quote Link to comment Share on other sites More sharing options...
Xnke Posted August 12, 2012 Share Posted August 12, 2012 ITM pistons are available in +1, +1.5, and +2mm, I think. If you have a set of L24 rods to prep, then some of the truck pistons with a 35.5mm pin height are available in a dished piston as well. Quote Link to comment Share on other sites More sharing options...
Lazeum Posted August 12, 2012 Share Posted August 12, 2012 I see 3 explanations: - Defect in piston casting (very unlikely) - Ring gap was not in spec - Ring did not overlap properly the center wavy ring (I forgot the correct name ) Quote Link to comment Share on other sites More sharing options...
calpoly-z Posted August 12, 2012 Author Share Posted August 12, 2012 Good to know that pistons should be available regardless of how much needs to be bored. All I have are the stock L28ET rods right now and they have already been balanced and prepped with ARP studs so I would prefer to stay with them. The main issue I think I'm going to face now is finding a machine shop locally with some experience working with these engines. West Texas is pretty much a domestic only market. Quote Link to comment Share on other sites More sharing options...
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