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Destroyed LS6: Cause and Pics

7K views 24 replies 19 participants last post by  Subdriver 
#1 · (Edited)
For those that have been following my rookie season in the SCCA T1 class, you know that I seized my motor on July 4th at Roebling Road.
With the significant help of my brother-in-law, we swapped the motor out with a new LS6 crate motor and I got back out on the track in St Louis July 27th for 2 of 3 in class and 2 of 24 overall.
While the car was at my brother-in-laws shop, he took apart the old motor. I thought many of you might be interested in the cause and like to see some pictures.
As I previously posted, I thought my lower than normal oil pressures might have contributed to the death of my motor. My hot idle oil pressure was 25 psi. Turns out I was probably wrong.
We strongly believe the cause of the engine failure was insufficient clearance between the crankshaft and the rod bearings on pistons 3 and 4, a factory defect. This belief is based on the destruction of rod 3 and significant heat markings on the crankshaft where this rod was. Since there are four rods downstream in the oil flow path of rod 4 and they were fine, I do not believe the low oil pressure contributed to this failure. I could be wrong as I'm certainly not an expert on this. But my brother-in-law has built and seen the inside of many engines and he is confident the gap was too small. However, he also felt this motor probably would've stood up to a 100,000 miles of normal usage. Unfortunately, my usage wasn't normal.
We also noted something else that may be a factory installation problem, but we're not sure. We found the lifters, which have a small square oil port on one side of them, were installed inconsistently. The oil flow path on the block is on one side of the lifters, but some lifters oil ports were 180 out from this path. However, the heads, valves, pushrods all look fine, so this may not be a problem. We need to do a little more research to see if these are supposed to face one direction or the other or if it just doesn't matter.
Prior to installing my new motor, my brother-in-law took it apart, checked the gaps between the crankshaft and the rods, checked the torques of all bolts, and verified the lifters were all in with the oil ports facing the path on the block. Everything checked out fine on my new motor. I'd like to get this one on a dyno as it feels noticeably stronger than my old one.



The oil drain plug - a magnetic one I had installed shortly after buying the car. This didn't bode well for the inside of the engine.



The oil pan with many parts of rods 3 and 4 and pistons 3 and 4.



The spot on the crankshaft where rod 3 should be. Note the blueing of the crankshaft where the rod was.



The majority of rod 3.



The top of piston 3 showing a crack where it impacted the head (spark plug?), and marks from the valves.



Looking down the shaft of rod 4 into the bottom of piston 4. Note you can see half the pin that holds the piston to the rod. There should be piston covering this pin. This rod had all but pulled the pin out of this piston as well.



Four of the lifters. You can see the small square oil port on the left three. The fourth one is 180 out from the other three and you can't see the same little small square oil port.



Six more lifters showing one oil port down, two up, one down, two up.



Picture of a head for those that haven't seen one. The heads actually survived this with only the loss of a few valves. The heads themselves are somehow unscratched.
 
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#8 ·
Thanks Brad for the update. My 94 Z28 mtotor blew when I was giving a track ride. So, not even hitting it that hard, rounding T9 at Seattle Int'l. Made a loud mechanical noise. I didn't know what to do, so continued around the track. Big mistake. Anyway, Mine was the main bearings. 2&3. The motor always had good oil press. So, now, do we all take the pans off and check bearing clearances?
and my Explorer is acting up. .I type, the cursor moves slowly across the line. with no letters showing up. after a bit, all the letters I just typed show up any computer types on this thread ale to help?E-mail off list. bobz28@msn.com
 
#9 ·
Great Post. Sorry to hear about your problems. Sounds like your new motor should get you back on the track...hard to believe that there could be those types of problems in the LS6. Hopefully your defective motor was the exception rather than the rule..:-?
 
#11 ·
Sorry to hear about your motor. :( In regard to the orientation of the lifter oil holes: According to GM, it doesn't matter. I have torn apart and built a ton of LS1/LS6 motors and the lifters are never installed in a specific orientation from the factory.

Jason
 
#12 ·
Jason,
Thanks for the info on the lifters. That is good to know.

Brian,
Once I decide what to do with this motor, I will get in touch with you about parts. At this point I am torn over rebuilding the motor stock so I have a spare SCCA T1 motor, or significantly upgrading it and turning the car into the DE car to beat all DE cars. :D
 
#13 ·
Great pics, sad story. It's amazing how little it can take to trash an engine. My dad and I built up a 327 to use in a boat, back in the '60s. Ported and polished the heads and intake, added a 3/4 race cam, etc. On it's maiden voyage it seized up. Disassembly showed that a single strand of metal from a wire brush got stuck in the oil pressure relief valve in the oil pump ... bye bye motor.

Sorry for your misfortune. :cheers:
 
#14 · (Edited)
From the 2002 Factory Service Manual

Section 6, page 6-408 - Valve Lifter Installation

It says:

"Insert the valve lifters into the lifter guides. Align the flat area on the top of the lifter with the flat area in the lifter guide bore. Push the lifter completely into the guide bore."

Subdriver, how does this correspond to what your seeing? It said nothing about the oil port orientation. It sounds like they can be put in one way, or turned 180 deg from there. It sounds like the oil port will work in either orientation.
 
#15 ·
"Insert the valve lifters into the lifter guides. Align the flat area on the top of the lifter with the flat area in the lifter guide bore. Push the lifter completely into the guide bore."
Good find. I don't really know what this means to be honest with you. I didn't actually pull the lifters out of the guides bores so never saw the flat area referred to above. I would guess this means there is a flat strip in the top of the lifter that would allow it to go in in two different ways (180 out) as I saw. All my lifters were definitely in one of two orientations, oil port up or down as they are laid out in the pictures above. This really corresponds to outward or inward on the head when the guides are installed.
I defer to what Jason said above. He sounds like an expert. I fully admit I am not.
 
#16 ·
Even though Chevy says its OK, when I saw 25 psi hot oil pressure it gave me the hebbiejebbie's. I immediately switched to 15W50 Mobil1 for all racing and hot summer driving. Hot oil psi is now always in th +40's and my blood pressure is slightly lower.

I just make sure the engine has a sufficient warmup period, the collant and poil temps are up before driving and I always change back to 10W30 when the ambient outside temp drops below %0 degrees.

No problems.....knock on wood.
 
#17 ·
The way I read the quote from the srvice manual, there is one flat spot in the lifter guide bore and one flat spot on the lifter. That tells me the lifter will only go in one way. Now if either one of the componets had 2 flat spots, you could install the lifter using either of the 2 flat spots.
Is that how you guys read that, or am I off in left field. :-? :-?
Also, was there any scoreing of #3 or #4 cylnder walls? The reason I ask is I am wondering what held the piston in place while the piston pin was being pulled down through the piston skirt?

P.S. Sorry about your engine and thanks for the pictures.

Russ
 
#19 ·
Even though Chevy says its OK, when I saw 25 psi hot oil pressure it gave me the hebbiejebbie's. I immediately switched to 15W50 Mobil1 for all racing and hot summer driving.
DJ,
Sorry I didn't clarify this. I have been running 15w50 Mobil 1 all season. Those oil pressures were with this oil. New engine is much closer to 40psi hot at idle. And I too warm the car up to normal temps prior to going out on the track.

The way I read the quote from the srvice manual, there is one flat spot in the lifter guide bore and one flat spot on the lifter.
Russ, I read it the same way, but it could go in two ways if this flat spot is on the top of the lifter not the side (i.e. a line running down the center of the top and one in the bottom of the guide bore. I'm not sure if this is correct. Maybe I'll have my brother-in-law take one out and take a pic for me (the dead engine is still in his shop in Norfolk).
Any yes, the cylinder walls in cylinders 3 and 4 are scored. The sleaves will need to be replaced. I couldn't get a clear picture of these. Sorry.
 
#20 ·
I have been running 15w50 Mobil 1 all season. Those oil pressures were with this oil. New engine is much closer to 40psi hot at idle. And I too warm the car up to normal temps prior to going out on the track.
From this quote ,it sounds like your original engine,did have clearance isues from the factory.....
 
#23 ·
Looks like the intial suspicions were correct...;-( I am glad to hear you have rebounded and are back on the track.

Great post and great pics. Lots of your fellow Z brothers will come to understand the internals and terminology better as a result....

What is this quote about a DE car from hell and a 427? Just in case that smiley did not mean you were joking... ;-) Don't do it... My advice is to "stay the course"... T-1 spare at your leisure.... ;-) If you don't need it, you can always sell it. Of course you can also build the 427 and sell that ;-) After a season like you have had-- DE will put you to sleep. ;-) Zzzzzzzzz.....

Good Luck.

PS. Yeah, let see a dyno pull on the new engine.... ;-)
 
#24 ·
Thanks for sharing hte pics. Sorry about the loss. The next powerplant should be bigger, better, and faster!
 
#25 ·
Are you going to pursue this with GM?
I am trying to get this info to GM to help prevent this from happening to someone else's motor. As I am racing my car, I hold out near zero hope that they will actually decide to pay for the replacement which I have already installed. Cost of racing.

What is this quote about a DE car from hell and a 427?
Joe, I was more thinking about what to do with the car in a few years when the C6 Z06 makes my car uncompetitive in T1 and I am on a duty assignment where I can't spend the time with a full SCCA T1 effort. I have the DE car to beat all DE cars already. With a 427 in it... :eek:
 
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