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clay
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1972 Chevrolet Nova

PostPosted: Sat Apr 17, 2010 3:04 pm    Post subject: Beginning of the post mortum Reply with quote

Started tearing it down this morning. I'm guessing when part of the piston is welded to the cylinder that's a bad thing........



A piece of ring got into the cylinder next to the bad one and probably pinched the top ring land.
Fuel wash in the chamber is sort of interesting though. I've never really seen this before because I've never torn down an engine that basically got shut off full throttle and then torn down.


I'll get more pictures tonight. Right now I've got to leave and take my daughter to a birthday party at Chuck E Cheese. Oh boy what fun........Clay

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240Z8
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1972 Datsun 240Z

PostPosted: Sat Apr 17, 2010 7:17 pm    Post subject: Reply with quote

Sorry to see the carnage.
Ahhhhhh... Chuck E Cheese. AKA the headache palace. You're a good dad.. Have fun!!! Laughing

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Skunkworkx
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1968 Chevrolet Camaro

PostPosted: Sat Apr 17, 2010 7:59 pm    Post subject: Reply with quote

Damn...

Were you spraying it ? Looks like the top rig butted ?

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clay
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1972 Chevrolet Nova

PostPosted: Sat Apr 17, 2010 11:53 pm    Post subject: Reply with quote

O.k. - here is some more ugly. If I can get the aluminum off of the cylinder wall, everything else should be not to bad from what I have found so far.


Bearings and crank look the same as when it was assembled. I'm especially happy to see that with the oil pressure fluctuations I have seen on shutdown.


I only knocked this piston out right now. I'm going to try to knock out a few more and try to tell if maybe the rings did but and measure what the ring gap is. One thing I didn't post a pic of yet is the amount of reversion that was taking place back into the intake ports. The camshaft I had in it was way wrong for a turbo application but I was using it to sort out some things before I pulled it to swap it. Reading some of Vizards stuff, this could have contributed to what happened. If have more pressure in the exhaust than the intake (as there is on a lot of turbo setups) then during the overlap time, exhaust will travel back into the intake and heat the incoming charge and make it more suceptible to detonation. I'll take a pic of the ports tomorrow to show everybody what I'm talking about. Clay

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Knarley Darley
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PostPosted: Sun Apr 18, 2010 2:26 am    Post subject: Reply with quote

If I had to guess what happened without knowing anything about the set up or induction, the first thing is detonation, but not from timing or being too lean. It actually looks like it lost oil control for some reason, and the oil in the chambers caused the detonation which started the carnage. You should be able to get the aluminum off the walls and clean up the cylinder. At least it didnt detonate bad enough to turn the bearings Black. Were the bearings still tight in the rod? or did they just fall out?
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10sec.et
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1969 Oldsmobile Cutlass

PostPosted: Sun Apr 18, 2010 2:41 am    Post subject: Reply with quote

Knarley Darley wrote:
If I had to guess what happened without knowing anything about the set up or induction, the first thing is detonation, but not from timing or being too lean. It actually looks like it lost oil control for some reason, and the oil in the chambers caused the detonation which started the carnage. You should be able to get the aluminum off the walls and clean up the cylinder. At least it didnt detonate bad enough to turn the bearings Black. Were the bearings still tight in the rod? or did they just fall out?


X2. i think its hydrochloric acid that is used to get the aluminum off of the cylinder wall but i have to double check that. when i get time, im going to post this in the turbo section on yellowbullet and see what those guys think. Clay, can you give me a quick rundown of the combo ?

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Knarley Darley
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PostPosted: Sun Apr 18, 2010 4:40 am    Post subject: Reply with quote

Is it possible the turbo seals blew and started blowing oil into the intake? That is definitely detonation that killed it. If the ring butted it would have just broken the piston, but wouldnt have looked burned at all, and if it was lean it looks melted without all the pitting and very rough surface that you have.
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af2
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1933 Willys Coupe

PostPosted: Sun Apr 18, 2010 4:46 pm    Post subject: Reply with quote

Knarley Darley wrote:
Is it possible the turbo seals blew and started blowing oil into the intake? That is definitely detonation that killed it. If the ring butted it would have just broken the piston, but wouldnt have looked burned at all, and if it was lean it looks melted without all the pitting and very rough surface that you have.


Kind of my thought also. It wouldn't take long to lift a ring.
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clay
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1972 Chevrolet Nova

PostPosted: Sun Apr 18, 2010 11:59 pm    Post subject: Reply with quote

The bearings fit back in the rods just like new, no signs of being curled in. Went and looked this morning to be sure but all of the plumbing from the turbo's to the engine is dry - no signs at all of any oil issues there. I'm leaning toward it being combination of issues that weren't quite right but added up to a big problem. I was running it a little lean, but not really excessive. Running pump gas (even though I get it at the same station about all the time) leaves room for not knowing what sort of octane or mix you have from tank to tank. It was the hottest day I had run this combination in so far - not hot by any means - but that would drive intake temps up a little more. Camshaft being wrong appears to have caused a lot of exhaust reversion back up into the intake ports (I'll get a picture of the ports to show everybody what I'm talking about - they look like exhaust ports with probably not over 500 - 600 miles on the turbo setup) I haven't knocked any more pistons out yet to check rings gaps. I have to ask why you think it is an oil control issue - not doubting anything you say, just trying to learn what you see that is leading you that way.
Here is the combo. 374 cubic inches (4.125" bore - 3.500" stroke), JE flattops, AFR 210 eliminator heads (75cc chamber for 9.3 compression ratio), mechanical flat tappet (252* in at 0.050" - 260* ex. at 0.050, 1.6 intake rockers, 1.5 exhaust rockers), Super Victor intake with some plenum work, CSU 830 carb, e-bay turbos with the following specs - 57mm x 75mm x 0.070 A/R cold side - 58mm x 74mm - 0.068 A/R hot side T4 compressor and turbine. Homemade log style manifolds. Air to air intercooler. TH400 with custom 9 1/2" converter, GearVendors and 3.73 gears. 28 x 10.5 slicks, car weight approx. 3800 lbs. Hadn't gone over 15 lbs with this setup on turbo's yet, had run over 20 with previous Procharger setup. Timing on this pass was 28* using 93 octane (supposedely......). Feel free to toss out any ideas. Thanks, Clay

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1979 Chevrolet Camaro

PostPosted: Mon Apr 19, 2010 1:36 pm    Post subject: Reply with quote

What's interesting to me is the consistent pattern on the combustion chamber. The intake side is clean from the fuel washing it down as it enters. The exhaust side looks excessively sooty, supporting your theory the camshaft timing is allowing the exhaust back into the cylinder heating things up and causing the failure.

Is this cylinder closest to the turbo in terms of exhaust path length? I would think if excessive back pressure is building up then the first cylinder to fail would be the closest one to the turbo.

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robins44
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PostPosted: Mon Apr 19, 2010 3:50 pm    Post subject: Reply with quote

10sec.et wrote:
Knarley Darley wrote:
If I had to guess what happened without knowing anything about the set up or induction, the first thing is detonation, but not from timing or being too lean. It actually looks like it lost oil control for some reason, and the oil in the chambers caused the detonation which started the carnage. You should be able to get the aluminum off the walls and clean up the cylinder. At least it didnt detonate bad enough to turn the bearings Black. Were the bearings still tight in the rod? or did they just fall out?


X2. i think its hydrochloric acid that is used to get the aluminum off of the cylinder wall but i have to double check that. when i get time, im going to post this in the turbo section on yellowbullet and see what those guys think. Clay, can you give me a quick rundown of the combo ?


yup muriatic acid
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af2
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1933 Willys Coupe

PostPosted: Mon Apr 19, 2010 5:15 pm    Post subject: Reply with quote

X2 on the Muriatic Acid. Most hardware stores have it.

What I saw as oil must be the fuel wash as you stated. Pics are harder to see things than in person.

Smoke is correct. The reversion looks extreme.

Were the pistons 2618 or the 4032 SRP. The 2618 is going to be way more forgiving in a boosted or prone to detonation atmosphere. The 4032 will break because of the extra silicon content making the piston harder compared to the 2618 material.

The exhaust log is not helping reversion. I would get a cam ground giving all information you have. Even rod length is critical to what grind you need.
I would question them is they didn't want to grind on a 114 LS.

If you can, use some sort of gauge to check the beams on the rods just to make sure nothing moved.
I use a machined round to gauge and run it up and down the H to see if things are separated or got tight.

I wish the best.
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clay
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1972 Chevrolet Nova

PostPosted: Tue Apr 20, 2010 12:14 am    Post subject: Reply with quote

Quote:
Is this cylinder closest to the turbo in terms of exhaust path length?

Yep, this cylinder (#4) and what would be #3 on the other bank actually have about a line of sight to the turbine entrance. I knocked the rest of the pistons out today and looked at the ends of the top rings with a magnifying glass. I didn't see any signs of the rest of them butting. The scratches left by the ring gap grinder were still clearly visable. #6 is definately toast also - a piece of ring went down beside the piston and pinched the top ring pretty bad. I measured all the pistons and they measured 4.1195" - 4.1205" except for the burnt one which was 4.116" meaning maybe detonation collapsed the skirt some????? Assuming the bore is 4.125" (my dial bore is at my buddies house) that puts the clearance slightly above what JE recommended (0.004"). I measured ring gaps on two cylinders and they were 0.026" and 0.028". The pistons were the 2618 alloy. There are plenty of signs of extreme reversion and the camshaft is definately going to change. Clay

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10sec.et
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1969 Oldsmobile Cutlass

PostPosted: Tue Apr 20, 2010 3:11 am    Post subject: Reply with quote

clay wrote:
I have to ask why you think it is an oil control issue - not doubting anything you say, just trying to learn what you see that is leading you that way.


"think" being the operative word here, im just basing my assumption on the carnage that ive seen others have. then again, it could have just been some crappy fuel. i need to do some more research before trying to push you in a specific direction. im still going to see what the turbo guys on YB have to say. i just havent had time.

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clay
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1972 Chevrolet Nova

PostPosted: Tue Apr 20, 2010 8:18 am    Post subject: Reply with quote

Oops, that cylinder doesn't have a line of sight to the turbine, the front cylinder does. However the front two intake ports are noticably darker with soot than the rear two intake ports on each head - hmmmm - I'm still thinking Smoke may be on the right track. Don't worry about being in a super big hurry about posting on YB, it's going to take a month or so for me to round up the parts before I start to reassemble. Clay
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