2eighTZ4me Posted June 4, 2009 Share Posted June 4, 2009 After having a bad smoking issue from the #5 cylinder (fouled a plug and found it was #5 ), I found a mule motor out of an 81ZX to get me by for my DD. Mule motor is in. Finally tore down the "smoking gun". Every single top compression ring was broken. All 6 cylinders. Mind you, I don't know if it occurred during the disassembly when sliding the pistons out of the bore, or whether they were broken when the motor was running, but nonetheless, they were all broken. Some broke in 2 pieces, a couple broke into many pieces. All middle compression rings were intact. I'm guessing the #5 cooling issue was the culprit, as the #5 piston's ring lands between the top and middle compression ring were melted. Fused a portion of the ring to it and all. Chipped a piece out of both sides of the piston at the upper ring land. It was fugly..... So, I had been running this motor in excess of 5,000 miles with the smoking problem. Put 350 miles a week on the car (and gallons upon gallons of oil!) - not knowing what the issue was. Even when I tore the head off, the bores were smooth as a baby's behind with no galling or anything. (bottom end had over 120K miles on it) It wasn't until I pulled the pistons that I discovered the cause. Oh - and my block also had 6 HeliCoil's in it for the head bolts. I used the ARP studs that put most of the thread tension on the top of the stud instead of in the block. Put over 30K miles on the block with 6 HeliCoils holding in the studs with no problems whatsoever. Anybody care to take a wag at why ALL my top rings broke, and why my #5 cylinder only was the one that suffered the ring land failure? I know detonation can do things like this, but I ran very moderate timing (34 degrees at 3k RPM) so, I'm curious how that much damage could have been done without boost, correct timing, and without the car ever overheating. Quote Link to comment Share on other sites More sharing options...
MikeBZ Posted June 5, 2009 Share Posted June 5, 2009 I've heard of high mileage rings breaking when the piston pops out of the block, but all 6 broken ?? Were there any pieces of the rings in the oil pan? I've heard L-series short blocks can go 250k between rebuilds if not abused... Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted June 5, 2009 Author Share Posted June 5, 2009 No pieces in the oil pan - they'd have to pass the second compression ring AND the oil ring to get down there. Nope - they were all just flopping about inside the top ring land. Isn't that funky? I took pics last night but left my camera at home today! Arrrgh! Quote Link to comment Share on other sites More sharing options...
The love of JDM Posted June 5, 2009 Share Posted June 5, 2009 Dang Tim, that sucks... this happend with the other motor or the recent one? Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted June 5, 2009 Author Share Posted June 5, 2009 No no no - the motor I got from you is humming away nicely. No complaints whatsoever. The one I'm talking about is the one I took out to replace with yours. It had seen its' better days apparently - but yeah - I was shocked that all 6 top compression rings were shattered. Some broken in two, some were broken in about 10 places, and pieces of ring came raining down into the catch pan. NEVER had seen that before, and I've torn down a LOT of these motors before when I worked for ZCar Atlanta. Hoping someone out here can give me some insight as to what happened! Quote Link to comment Share on other sites More sharing options...
hoov100 Posted June 5, 2009 Share Posted June 5, 2009 I've heard L-series short blocks can go 250k between rebuilds if not abused... thats a VERY conservative estimate for the L-series i had 255k on my 81 and that car was ABUSED, three of the head bolts where broken, two of the cam tower bolts where broken, didnt change the oil the entire time i owned it, over heated it a couple times, was running super lean and would detonate in neutral and I'm sure the valve seals where going out also, still fired up for me every morning no problem, never left me stranded and ran great up to the day i loaded it onto the transport to its new owner! my old neighbor has close to 500k on his 280z and doesnt burn any oil and has never had any sort of real work done on it, minus a water pump change. Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted June 5, 2009 Author Share Posted June 5, 2009 Another testament! Hear hear! Please step up to the docket and confess your sins O' ye abusers of the L!! I love these "war" stories! Keep 'em coming. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 5, 2009 Share Posted June 5, 2009 I put an 80ZX 2+2 engine with 186,000 miles into my Fairlady Z. It now has 225,000+ on it, spun 147 to the rear wheels and runs 15.30 to 15.50 inthe 1/4 mile. All cylinders have 180 psi of compression. It uses oil, depending on how I drive, depends on how much I use. Highway driving is less than Auto-X. You can smell it behind the car... Plugs don't foul, it just burns oil without smoke. "I have others..." Quote Link to comment Share on other sites More sharing options...
70 Cam Guy Posted June 5, 2009 Share Posted June 5, 2009 I normally just read and learn on HybridZ but when I built the engine for my old Camaro, I had to gap the piston rings and file some to get the minimum clearance. I don't know if that is necessary on the L series engines but it sounds like a possibility if all your rings broke with no serious problems in the past -Andy '73 240Z Quote Link to comment Share on other sites More sharing options...
Turbo7MN Posted June 5, 2009 Share Posted June 5, 2009 thats a VERY conservative estimate for the L-series i had 255k on my 81 and that car was ABUSED, three of the head bolts where broken, two of the cam tower bolts where broken, didnt change the oil the entire time i owned it, over heated it a couple times, was running super lean and would detonate in neutral and I'm sure the valve seals where going out also, still fired up for me every morning no problem, never left me stranded and ran great up to the day i loaded it onto the transport to its new owner! my old neighbor has close to 500k on his 280z and doesnt burn any oil and has never had any sort of real work done on it, minus a water pump change. Haha... did the new owner know about any of this? Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 6, 2009 Share Posted June 6, 2009 I normally just read and learn on HybridZ but when I built the engine for my old Camaro, I had to gap the piston rings and file some to get the minimum clearance. I don't know if that is necessary on the L series engines but it sounds like a possibility if all your rings broke with no serious problems in the past -Andy '73 240Z When I lived in Japan, my Japanese Friend who was into Mustangs kept quizzing me about things he thought were 'odd' about building the Ford engine...the biggest thing that irked him was the fact that you had to make the rings fit! He never understood, and always asked me why they weren't like Nissan or Toyota rings that 'fit right out of the box'... I also couldn't answer another difficult question he had at that time, which was why contentious UAW workers were chanting 'shut em down'---he says 'If the company closes, won't they ALL be out of work? Why do they want to do that?' This was 1986 when he asked me that question... I couldn't answer it then, still cant! Best I could do in both cases was say 'It's always been that way with them!' American Piston Rings and the UAW, that is! Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 6, 2009 Share Posted June 6, 2009 I went through ASE certification in MICHIGAN of all places, but having had numberous VW engines apart it always raised questions as to why American OEM's did what they did. When I got exposed to Japanese Engine Guts, it was all over again new... Growing up under the wing of Big Daddy GM and Ford who donated copious ammounts of engines, cars, whatever to the local Auto Tech programmes at the high schools, I got spoiled. We had guys directly from Champion Spark Plug in Flint come up and give presentations to a high school auto shop class... And when the more advanced students showed interest in what was going on, the guys were more than willing to take some time to go in depth on their subject expertise... Really, I think they were cultivating their next generation of field trainers and seminar presenters... but it was all good. The biggest mistake my old high school made was turning the auto shop and machine shop (and likely the wood shop as well) into a computer lab. I personally know of at least three people that came from that program in two years attendance that were taken into GMI, or other 'feeder programs' for the Big Three OEM Representative grooming programs. Yeah, that's roughly 1% of the population that graduated from the school those two years. Had I accepted my apprenticeship to M-B that would have made 4 out of 259 students going directly to OEMs straight out of high school. Over 2% when you consider the guys that went directly to dealerships to work, or on to feeder technician programs. What do those guys do now? Sit behind a computer and get bored stiff waiting to get outside and work on their cars? It's a shame, really it is... Quote Link to comment Share on other sites More sharing options...
Ferrariferg Posted June 6, 2009 Share Posted June 6, 2009 I have a couple of them. My DD sat for over 7 years and all I had to do was put a battery in it and fired right up. My donor Turbo car had just under 300,000 on it and it still ran strong. I recently started to tear the motor down and All of the cylinder bores are still smooth, no scaring, and you can still see the cross hatching. Turbo didn't have much shaft play for having so many miles. Quote Link to comment Share on other sites More sharing options...
hoov100 Posted June 6, 2009 Share Posted June 6, 2009 Haha... did the new owner know about any of this? i told him it had a slight knock and probably needed a new head, doesnt really matter much anyway as i think he shipped it to the middle east. Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted June 6, 2009 Share Posted June 6, 2009 How were the piston skirts? I bought an engine from someone here and found 5 and 6 had broken skirts. I had another engine.........a N/A f54 that a hurricane had filled with the cylinders with inches of water to the point that a crust of rust formed where the water level was the highest that I had to poke through just to see the piston tops. I knew that the rod bearings were new and that the rods had seen zero abuse so I used a 3 foot prybar and a big hammer to hammer them out putting dents into the pin bosses as I hammered them past the rusty bores. I figured I would only keep the rods and bearings. Once they came out, I looked and found no broken ring lands and decided to soak the piston/rod assemblies in carb cleaner which cleaned everything up and I spun the rings around until the grooves were spotless. I honed the turbo block that had the broken piston skirts and installed the n/a flattops and the engine is perfect.......no burning oil and perfect compression. I put it into my M30 infiniti and drive it every day. Quote Link to comment Share on other sites More sharing options...
Guest JoeGasm Posted June 7, 2009 Share Posted June 7, 2009 Bought a 280ZX, owner never told me it had cooling problems. I kept fixing culprits before another came up. First a crack in the hose, then after that came a heater core, etc., etc. One day it overheated. Disgusting. I sent it to get it rebuilt since the head had cracked, and the only damage was literally a crack in the head. Pistons, rings, etc. were all good, but I still replaced them. Quote Link to comment Share on other sites More sharing options...
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