stprasinz Posted February 4, 2008 Share Posted February 4, 2008 Well I have been having trouble blowing head gaskets. First one, ok just pushed the gasket out, from repeated high boost runs... Second one wow that was quick, I didn't even run high boost only a few times (and it wasn't even HIGH BOOST, like I have in the past?) Replaced it a 3rd time and blew it in less then 1 mile... Ok maybe not the heads problem... Pulled the motor got the other one prepped(flat top ouch..). Well anyway I get all ready for the swap and pull the oil pan off the oil engine, and low and behold, there is a metal chingky sound in the bottom... So I put my habd into the pan and pull oil a alluminum peice?? Looks like the bottom of a piston skirt???Wait more chingky noise.. Its another, and another??? Sure enough all 6 piston skirts got busted off by the crank shaft????? Needless to say...... Boy I guess I am not going to that machine shop again.. And I guess that may be why I kept thinking my turbo was leaking oil... Gonna giv ethe shop a call today..... How do I calmly approach the situation??? Oh and here is the odd part. I have rotated the engine by hand several times.... (on initial assembly) And it spun freely( so I thought) I guess I didn't catch that one.. And yes I bought the pistons from them... Over 300 Said they where a step above cast allthough they weren't hyper's??? Didn't ask I mean he's the machine shop..... Add that to the balancing, cranck machining, block machining, rod prep.... dip etc... the tune of approx 900. So like I said how do I approx the situation calmly... any advice... Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted February 4, 2008 Share Posted February 4, 2008 Wow another New Yorker! Sorry to hear about the poor piston fit. If the shop built the whole motor, how long ago was it? Have you changed anything on it since they built it? How many miles did you put on it since it was built? All of this will determine your course of action. Hopefully, if you give them all the facts, and they are reasonable, you can come to some sort of an agreement. Maybe they will have the motor re-done at their cost, or partially their cost. Are you sure the crankshaft broke the skirts or was it the connecting rods? List the parts that were used in the rebuild. You need all of the FACTS to solve this one. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted February 4, 2008 Administrators Share Posted February 4, 2008 DETONATION!!! The L-series is especially quite sensitive to boost “issuesâ€. Your engine is Detonating itself to death. Broken piston skirts, three blown head gaskets, DING DING DIGN!! Detonation!!! Your crank was NOT hitting your pistons. The assembler would have seen/felt that happening during assembly if that were the case. If the combination of parts, (pistons, cylinder head for a pump gas friendly compression ratio), and the tune, (ignition timing, fueling requirement using an aftermarket EMS or an OE Turbo EMS). What parts are you running, i.e., dished or flat top pistons? What cylinder head, i.e. casting number on the passenger side? Also, what engine management system are you using? Was the person/s tuning your engine knowledgeable and more importantly experienced in tuning boosted engines? On the first blown head gasket, the red flag of detonation was waving. The second blown head gasket, was your DEAD giveaway as to the problem, DETONATION and action to rectify the detonation should have been implemented by this point(actually the first time the head gasket blew, should’ve been the clue that something is wrong and something should be changed before it happened again). The detonation is taking place on one side of the combustion chamber which is forcing your pistons to rock violently which slaps the piston skirts against the cylinder wall, breaking the bottom of the skirts off the pistons. With detonation this severe, Good chance your rings and ring lands are also collapsed/busted! Your rod bearings may even show signs of being squished as well, depending on the severity of the detonation and how long it has been going on, (apparently several times). other issues such as cracked crankshaft etc could arise... In short, your entire short block needs to be completely torn down, new pistons, maybe new bearings, etc. Searching the archives here on HybridZ, make sure your new pistons and head combination are compatible with each other under boost. Also, search the archives here for appropriate tuning parameters for builds similar to yours. Always start out your boost levels, fuel requirements, and timing advance on the conservative side. Here are a few pics borrowed from other threads, Turbo L-'6s that experienced detonation. This is the region of the piston skirts that bust from detonation. Blown out head gasket from detonation. Busted pistons from detonation. Notice the busted ring lands and pistons skirts... Quote Link to comment Share on other sites More sharing options...
stprasinz Posted February 5, 2008 Author Share Posted February 5, 2008 From the looks of the crank while rotating it is still close to the pistons where they where brokeand would have hit the pistons the skirts stuck well below the bottom of the cylinders. But yes thats where the pistons broke, also the closest plase to the crank. While rotating the crank the pistons clear by a very minute amount evn with the broken skirt. THe draw back is I did assembly. I rotated the engine by hand a many of times. I didn't feel anything I thought was a ubstruction, but it was also my first fulll assembly, other than sbc, and they feel 2 times as stiff while rotating just one cyl. than the 280 felt after full assembly... But I did purchase the pistons from this person, and he is known for some hand gernades. He did all the machine work, and I did the assembly. After I get the car done and out of the garage I will Toss the engine on the stand and take a closer look to see exact clearnace. Also all 6 pistons broke in the same spot. Exact same spot. If it was 1, 2 or even 5 I wouldn't think it was the crankshaft. Also there apear to be small dings in the crankshaft , But I guess that could be from the peices projecting away. Also when the machining was done the shop was talking about offcenter boring, because the engine had a rusted side on 1 cyl. where it satfor years, upon years with a shot hg causinbg the h20 to sit in that cyl, and rust seize. etc. I said I would rather sleeve it he said lets bore it and see. bored it a full mm over after I said I would rather .5 and sleeve that cyl. he didn't care what I said. And to top it off that cyl. was still "shadowed"? As in still some evidence of rust having been there at 1 time..... Anyway till futher inspection keep your widebands tuned for the z.... Quote Link to comment Share on other sites More sharing options...
slownrusty Posted February 6, 2008 Share Posted February 6, 2008 Couple of simple questions: 1) Define what you mean by "High Boost Runs" - how mch psi exactly? 2) What engine management are you using? Yasin Quote Link to comment Share on other sites More sharing options...
stprasinz Posted February 6, 2008 Author Share Posted February 6, 2008 High boost. 24psi low boost 18 All on the stock ecu, with larger cam, big intercooler, turbonetics 60-1, 450cc injectors, 1 mm overbored, n42 intake(heat wrapped), msd blaster 2 coil, stainless valves w/ undercut stems, alluminum flywheel. The list goes on. Now (as in still in boxes but to be installed int he next couple weeks) I have megasquirt, methanol injection, h2o intercooler, larger alternator, that list also goes on(wb o2)..... Oh and the 3 head gaskets were as follows. First head gasket after 1500 miles, repeatedly ran 24 psi of boost, repeat runs, and I made a few passes after starting and shutting off every 5 minutes for about 20 minutes (drag races) in between passes. the second was after I ran it for a while (about a month) I attempted to retorque the head at which point I busted a bolt, replaced all the bolts but not the hg. It was weeping after that point. The 3rd gasket was within 1 mile attempting to run 12 psi of boost. I think the 3rd time was a faulty ebay special gasket. The portioj that went over the timing cover was entirely crushed.. and I had already disassembled my head..... Oh I think I said that it had blown in the same spot befor.. Well it was the other side.... Same type of fault though.... And all that being said. I have read a few of braaps post and he seems to have a pelithera of knowledge on many subjects.. I am not saying he isn't right by any means. I am merely pointiong out more of the situation. And unfortunatley I am afraid he is right... If he is hopefully the megasquirt and meth inj cures that problem... Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted February 6, 2008 Share Posted February 6, 2008 24psi on stock~ish pistons?!?!?! Stock pistons are usually known to be good only to 18-19 PSI for any decent duration of time. Good forged pistons usually go from $550 to $1000+ with fancy coatings etc... They might help in not breaking off the skirts. Also how long do you warm the engine up before hitting any boost? Cold pistons are smaller and have more clearance in the bore than hot pistons. That means that they can "jam" and break off the skirt more easily than if warmed up. Just some of my thoughts... Quote Link to comment Share on other sites More sharing options...
z-ya Posted February 6, 2008 Share Posted February 6, 2008 From the looks of the crank while rotating it is still close to the pistons where they where brokeand would have hit the pistons the skirts stuck well below the bottom of the cylinders. But yes thats where the pistons broke, also the closest plase to the crank. While rotating the crank the pistons clear by a very minute amount evn with the broken skirt. THe draw back is I did assembly. I rotated the engine by hand a many of times. I didn't feel anything I thought was a ubstruction, but it was also my first fulll assembly, other than sbc, and they feel 2 times as stiff while rotating just one cyl. than the 280 felt after full assembly... But I did purchase the pistons from this person, and he is known for some hand gernades. He did all the machine work, and I did the assembly. After I get the car done and out of the garage I will Toss the engine on the stand and take a closer look to see exact clearnace. Also all 6 pistons broke in the same spot. Exact same spot. If it was 1, 2 or even 5 I wouldn't think it was the crankshaft. Also there apear to be small dings in the crankshaft , But I guess that could be from the peices projecting away. Also when the machining was done the shop was talking about offcenter boring, because the engine had a rusted side on 1 cyl. where it satfor years, upon years with a shot hg causinbg the h20 to sit in that cyl, and rust seize. etc. I said I would rather sleeve it he said lets bore it and see. bored it a full mm over after I said I would rather .5 and sleeve that cyl. he didn't care what I said. And to top it off that cyl. was still "shadowed"? As in still some evidence of rust having been there at 1 time..... Anyway till futher inspection keep your widebands tuned for the z.... As Paul said, this is not a mechanical interference problem, it is detonation, period. I just pulled apart my supercharged motor that had been pinging for a while (couldn't hear it over the sound of the SC), and the only reason the head gasket didn't blow was the fact that I had a metal one in there. All the pistons have broken skirts. Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted February 6, 2008 Share Posted February 6, 2008 You don't need detonation to do that as I have seen normally aspirated L28s do that. Another cause is running the engine hard while stone cold and the resulting piston slap knocks off the skirts as shown above. Quote Link to comment Share on other sites More sharing options...
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