cygnusx1 Posted August 31, 2007 Share Posted August 31, 2007 My head gasket blew out about a month ago and I finally got around to pulling the head. This happened during tuning on the street. I kept pushing the tune harder and harder until this happened. I now know the limits of the tune on a stock long block and have adjusted accordingly. There was no loss of coolant and oil. It was a plain compression leak. 130K miles and the hatch mark is still there! The walls are smooth as glass on all cylinders. Can you tell where the problem was? Cylinder #5 Quote Link to comment Share on other sites More sharing options...
mario_82_ZXT Posted August 31, 2007 Share Posted August 31, 2007 Thats exactly what happened to mine at the drags except it was the #1 cylinder and I spent a week chasing an exhaust leak Mario Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted August 31, 2007 Author Share Posted August 31, 2007 This began as a whistle-squeek-peep type of sound and then graduated to exhaust manifold leak sound. Eventually, it became obvious that it was at the head gasket. Of course, I was also fooled and changed the exhaust gasket first. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted September 1, 2007 Author Share Posted September 1, 2007 I used some eco-friendly paint stripper on the head and block mating surfaces. I let it sit for about an hour while I fabricated a heat shield for the turbo. When I went back to clean the head and block, the crud pretty much scraped right off with a plastic putty knife. I then long-block sanded both surfaces clean to 320 grit and checked for flatness. The head tapers down to a 0.002" low spot at the left rear corner. It's a long gradual taper so I think it's OK for now. I don't think I am going to have it milled because I am going to pull the whole motor and rebuild it next winter anyhow. It should be fine for casual use. I'll get up some more pics tomorrow. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted September 2, 2007 Author Share Posted September 2, 2007 I got the whole thing back together today and learned a few more tricks. I learned that you can install the intake manifold bolts into the head and then slide the intake into place from the top with the bolts loosely theaded into the head. This saves you from fishing blindly for the holes in the head with the bolts taped into a socket. I don't know why I never did this before. MUCH easier. After torquing the head down and installing everything , I turned the key and she fired right up strong. The only problem was that one of my pesky hydraulic rocker posts must have bled down while the head was on the bench. It would not refill so I had to take off the valve cover, the rocker and manually fill the hydraulic post. After I did that and got it idling nicely and quietly, I noticed that the motor was making a ton of whitish smoke on and off. It was like a smoke bomb. I was worried I had screwed something up. It got really bad so I started to tune the idle mixtures to see if I could cut back the smoke. After about 15 minutes of idling, the smoke cleared up and it's back to normal. I guess there was alot of oil in the intake tract that had to burn off. The motor runs strong and smooth, and even sounds better with the new head gasket. I am limiting to about 10 psi until I heat cycle and retorque the head studs. All is well for now! I even fabricated a nice stainless heat shield for the turbine. I'll get photos. Quote Link to comment Share on other sites More sharing options...
gearheadstik Posted September 3, 2007 Share Posted September 3, 2007 Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted September 3, 2007 Share Posted September 3, 2007 holy crap! the SAME EXACT thing happened to me on the track! Cylinder 5! right out the side of the block!! I think I still have pics on my putfile.com website.. i better LoL. this is strange.. wonder what causes the weakend HG on #5? Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted September 3, 2007 Author Share Posted September 3, 2007 I believe it's related to the cooling issues on the last two cylinders. They are the first two to detonate. Quote Link to comment Share on other sites More sharing options...
1 tuff z Posted September 3, 2007 Share Posted September 3, 2007 ahhh, once again back among the living-z's that is! Quote Link to comment Share on other sites More sharing options...
Tony D Posted September 3, 2007 Share Posted September 3, 2007 Got to look a bit closer there, gearheadstick's detonation issue is on the last three cylinders at least! not just 5&6, you can see 4 was also on the way out. You don't hear it all the time, guys. And like the old adage goes, once you'ver heard it, it's too late! Quote Link to comment Share on other sites More sharing options...
gearheadstik Posted September 3, 2007 Share Posted September 3, 2007 I didn't hear anything.....So I always start laughing at the guys at the track that tune by ear, and claim the just change the tune when they hear it....yea right... Quote Link to comment Share on other sites More sharing options...
fear_me Posted September 4, 2007 Share Posted September 4, 2007 Here is a thought, what about o-ringing the block? I have read on here that a couple people have done this, it will help keep the head gasket in place. Anybody try doing this as a fix for this problem? ~Andrew Quote Link to comment Share on other sites More sharing options...
big-phil Posted September 4, 2007 Share Posted September 4, 2007 I had a block with 185k on it, and it still had factory hash marks. My neighbor had to come over and see it to believe it! Quote Link to comment Share on other sites More sharing options...
Careless Posted September 4, 2007 Share Posted September 4, 2007 I had a block with 185k on it, and it still had factory hash marks. My neighbor had to come over and see it to believe it! i coulda' stuck new rings back onto my RB30 pistons and had it go right in and it would have still seated the rings! it still had the factory hones aswell! is this a nissan thing ?! Quote Link to comment Share on other sites More sharing options...
Poundz9oh9 Posted September 4, 2007 Share Posted September 4, 2007 Looks like a "race prepped" excellent running motor to me !! Well, according to Savage42's standards anyway, when he robbed me of about 4 g's on a motor I bought from him. Quote Link to comment Share on other sites More sharing options...
Guest s3030zman Posted September 4, 2007 Share Posted September 4, 2007 I blew out #5 on my z a few weeks ago to tell the truth i thought that i just had a header leak . I don't drive the 77 too much I have 8 zcars and not enuff time to work on them but anyways the starter was lagging and thought the starter was bad but to my suprize #5 cylinder was full of water . finally it turned over with a bang. the gasket blew out the side of my moter the only thing i'm wored about is i heard a loud bang and i don't have had the time to tear the moter down to see if it bent the rod have you all heard of that kinda thing damaging the rod ? well on the other hand i have all the parts i need just no time s3030zman Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted September 4, 2007 Author Share Posted September 4, 2007 O-ringing is fine and there is lots of info about that here. I street tuned it myself without the aid of a dyno or knock sensor. I really expected to find the limit. This motor is going to be totally worked next year anyhow. The factory head gasket was quickly replaced with another factory head gasket. It does it's job fine when the tune is proper. O-ringing the head without building the rest of the motor is like repairing a rock climbing rope with a single strand shoe lace. As far as I am concerned, the L28ET motor is one tough muttha...the head gasket is a "fuse" for those that want to find the limit of the stock long block, like me. I have added fuel to get a fatter mixture and pulled some timing at boost. It feels faster now at 10psi than it did with the previous tunes at 15psi. Quote Link to comment Share on other sites More sharing options...
Careless Posted September 5, 2007 Share Posted September 5, 2007 O-ringing the head without building the rest of the motor is like repairing a rock climbing rope with a single strand shoe lace. i'd say its the other way around. repairing a shoe lace with a rock-climbing rope. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted September 5, 2007 Author Share Posted September 5, 2007 i'd say its the other way around. repairing a shoe lace with a rock-climbing rope. I fall corrected. Quote Link to comment Share on other sites More sharing options...
Tony D Posted September 6, 2007 Share Posted September 6, 2007 O-ringing is fine and there is lots of info about that here. O-ringing the head without building the rest of the motor is like repairing a rock climbing rope with a single strand shoe lace... O-Ringing in this case would have resulted in blown pistons, ring lands, or skirts, instead of a $60 Gasket! Get your tuning down on as stock a setup as possible so you only break things like a cheap head gasket. After you get it tuned, then put your money into the block. Quote Link to comment Share on other sites More sharing options...
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