[Z06] Another LS7 down for the count
07-25-2013, 09:19 AM
#181
Melting Slicks
I've been real busy in the shop. So far no more updates, I did find the exhaust valve head. It is chewed up so that is an indicator that the head had broke off, and went into the cylinder where it got hit several times by the piston until the piston shattered. The valve head was found in the header where all the tubes merge together, along with a bunch of other metallic debris that was ejected out of the engine when the cylinder wall was broken out.
I have a new block in the machine shop now, the rods are at Katech getting bushed, the new pistons are here, so as soon as I get the rods back from Katech the engine work will start so we can get a engine together for Steve. The new heads are at LPE getting porting work, new springs and Ferrea valves installed. I have the new Ferrea hollow stem exhaust valves for Steve, they are 84 grams, which is 10 grams heavier than the stock exhaust valve. This valve is much lighter than the Ferrea super alloy valves I have been using, these not intended for boost unless it is kept at no more than 10 psi, per Ferrea. Once I have a date as to when I can expect engine delivery, I will pull the junk engine out, then when I get some time I will remove the head and give you guys some insight as to what the valve stem wear was in the failed cylinder.
I have a new block in the machine shop now, the rods are at Katech getting bushed, the new pistons are here, so as soon as I get the rods back from Katech the engine work will start so we can get a engine together for Steve. The new heads are at LPE getting porting work, new springs and Ferrea valves installed. I have the new Ferrea hollow stem exhaust valves for Steve, they are 84 grams, which is 10 grams heavier than the stock exhaust valve. This valve is much lighter than the Ferrea super alloy valves I have been using, these not intended for boost unless it is kept at no more than 10 psi, per Ferrea. Once I have a date as to when I can expect engine delivery, I will pull the junk engine out, then when I get some time I will remove the head and give you guys some insight as to what the valve stem wear was in the failed cylinder.
Thanks TJ!
08-29-2013, 05:15 PM
#182
Former Vendor
Thread Starter
Update on Madsens car, I got it apart today:
Drivetrain out of the car.
Cam is damaged
Cylinder head is wasted
Another shot of the carnage, this is the first Ti rod I have seen that was twisted. Goes to show how tough these things really are. I found metal scattered all over the K member, the ejected debris came out at such a velocity that it damaged the oil cooler lines which will need replacement, and also dented two header tubes! The stuff hit so hard that had it been flesh it would have easily torn through human flesh as if it was shrapnel from a grenade!
I will get a guide measurement later today for those that was wanting to know.
Drivetrain out of the car.
Cam is damaged
Cylinder head is wasted
Another shot of the carnage, this is the first Ti rod I have seen that was twisted. Goes to show how tough these things really are. I found metal scattered all over the K member, the ejected debris came out at such a velocity that it damaged the oil cooler lines which will need replacement, and also dented two header tubes! The stuff hit so hard that had it been flesh it would have easily torn through human flesh as if it was shrapnel from a grenade!
I will get a guide measurement later today for those that was wanting to know.
Last edited by tjw@wpe; 08-29-2013 at 05:18 PM.
08-29-2013, 05:21 PM
#183
Wow, what a mess.
I had always expected the piston in this one to be somewhat intact, until I saw you say that the pistons were:
Out of curiousity TJ, how can you tell that this wasn't a piston failure that took out the valve?
Last edited by '06 Quicksilver Z06; 08-29-2013 at 05:48 PM.
08-29-2013, 07:29 PM
#185
Former Vendor
Thread Starter
http://www.youtube.com/watch?v=BPyap...ature=youtu.be
08-29-2013, 07:59 PM
#187
Definitely not a piston failure, the piston was intact for at least several cycles when the valve broke. You can see serious damage as a result of the valve head being pounded into the combustion chamber before the piston said "OK I give up"
It appears these are stock heads that were "supposed" to be reworked. However the stock PM valve guides are still there, there are no bronze guides in these heads. Definitely had non stock solid SS valves installed on the exhaust side. Here is a short video of the guide wear. I know people wanted me to measure the guide wear but after checking it and seeing how far out it was, there isn't any sense for me to bother measuring it, you can see it!
http://www.youtube.com/watch?v=BPyap...ature=youtu.be
It appears these are stock heads that were "supposed" to be reworked. However the stock PM valve guides are still there, there are no bronze guides in these heads. Definitely had non stock solid SS valves installed on the exhaust side. Here is a short video of the guide wear. I know people wanted me to measure the guide wear but after checking it and seeing how far out it was, there isn't any sense for me to bother measuring it, you can see it!
http://www.youtube.com/watch?v=BPyap...ature=youtu.be
Im curious can you still measure it I just want data to see the wear also to benefit the forum as well. Thanks
08-29-2013, 08:31 PM
#188
Melting Slicks
Definitely not a piston failure, the piston was intact for at least several cycles when the valve broke. You can see serious damage as a result of the valve head being pounded into the combustion chamber before the piston said "OK I give up"
It appears these are stock heads that were "supposed" to be reworked. However the stock PM valve guides are still there, there are no bronze guides in these heads. Definitely had non stock solid SS valves installed on the exhaust side. Here is a short video of the guide wear. I know people wanted me to measure the guide wear but after checking it and seeing how far out it was, there isn't any sense for me to bother measuring it, you can see it!
http://www.youtube.com/watch?v=BPyap...ature=youtu.be
It appears these are stock heads that were "supposed" to be reworked. However the stock PM valve guides are still there, there are no bronze guides in these heads. Definitely had non stock solid SS valves installed on the exhaust side. Here is a short video of the guide wear. I know people wanted me to measure the guide wear but after checking it and seeing how far out it was, there isn't any sense for me to bother measuring it, you can see it!
http://www.youtube.com/watch?v=BPyap...ature=youtu.be
Thank you. As I feared. SS valve failure from guide wear. Granted the guides were still stock it seems. But it contributes to my theory that if you do not address the guide wear, SS or OEM, the valve will fail. No valve will be able to deal with that kind of stress.
Fix the guide wear fix the problem.
Thank you TJ for going out of your way to do this.
Last edited by propain; 08-29-2013 at 08:45 PM.
08-29-2013, 09:38 PM
#189
Definitely had non stock solid SS valves installed on the exhaust side. Here is a short video of the guide wear. I know people wanted me to measure the guide wear but after checking it and seeing how far out it was, there isn't any sense for me to bother measuring it, you can see it!
http://www.youtube.com/watch?v=BPyap...ature=youtu.be
http://www.youtube.com/watch?v=BPyap...ature=youtu.be
Guys, if you're having this procedure done, choose wisely when you decide which shop you're going to have do it.
Last edited by '06 Quicksilver Z06; 08-29-2013 at 09:44 PM.
08-29-2013, 09:47 PM
#190
No doubt.Who knows if this would have happened had bronze guides been used in this case?
I'm beginning to take even further to heart what Darin Morgan had to say about the stock guides and their propensity towards accelerated wear once wear starts.
08-29-2013, 10:09 PM
#191
Melting Slicks
I also agree, choose who does your heads wisely.
08-29-2013, 10:46 PM
#192
Blaming the guide (material) for being worn makes no more sense than blaming the valve for breaking in a worn guide.
The conventional wisdom in the engine building world is that a sintered iron guide, properly installed and not abused, will last longer than a bronze guide. Of course in many builds that type of longevity (say, 100K miles) is not a goal (say, for engines that may be rebuilt every season or three).
08-29-2013, 11:03 PM
#193
"The shoe wear is what caused you to cut your feet, not the shoe material".
Well why do you think that the shoe material wore out?
The conventional wisdom in the engine building world is that a sintered iron guide, properly installed and not abused, will last longer than a bronze guide. Of course in many builds that type of longevity (say, 100K miles) is not a goal (say, for engines that may be rebuilt every season or three).
The following exchange illustrates how opinions differ even among professionals.
Simply put, the OEM sintered guides are superior (all other things being equal) due to their hardness, wear characteristics, alloy and heat dissipation. There IS a reason OEM uses them - and its not because of bronze's availability or cost.
The issues are when other things interact negatively (geometry, tolerance, the valve design or coating, etc). Most of the big name builders here will say as much - the common denominator is sourcing (or working through those other variables).
The issues are when other things interact negatively (geometry, tolerance, the valve design or coating, etc). Most of the big name builders here will say as much - the common denominator is sourcing (or working through those other variables).
Okay then, I'm gunna have a hard time reconciling your experience with what Brian Tooley had to say on the subject...all be it his opinion seemed most directed towards street so maybe we can't assume what works for a race car will automatically work for a street car???
Powdered metal versus bronze guides
As many of you know I owned Total Engine Airflow from 1993 until 2004 when I sold it to Summit Racing and then worked with the guys at Trick Flow Specialties until 2010 where I developed every CNC program they have, as well as worked on new cylinder head designs. Of the dozens and dozens of used aftermarket heads with bronze guides that came into my shop using stock rockers, the number of heads that had what I would consider excessive guide wear (over .004”) was 100%.
There is no comparison in hardness between powdered metal guides and bronze guides. Powdered metal guides are far harder, and since they’re engineered with silicon they have good lubricity properties. I’ve checked OEM LS guides from a truck with 150,000 miles that only had .0001” of wear. Bronze guides when using stock rockers is a poor choice in my opinion, simply based on the guide wear that I’ve seen in my years of experience. I’ve seen bronze guides with 10,000 miles have .010” wear. Most shops never have the opportunity to check this. I’ve seen heads with no oil consumption or any other obvious issues have .010” of guide wear, this is a testament to how good modern valve seals are.
Powdered metal versus bronze guides
As many of you know I owned Total Engine Airflow from 1993 until 2004 when I sold it to Summit Racing and then worked with the guys at Trick Flow Specialties until 2010 where I developed every CNC program they have, as well as worked on new cylinder head designs. Of the dozens and dozens of used aftermarket heads with bronze guides that came into my shop using stock rockers, the number of heads that had what I would consider excessive guide wear (over .004”) was 100%.
There is no comparison in hardness between powdered metal guides and bronze guides. Powdered metal guides are far harder, and since they’re engineered with silicon they have good lubricity properties. I’ve checked OEM LS guides from a truck with 150,000 miles that only had .0001” of wear. Bronze guides when using stock rockers is a poor choice in my opinion, simply based on the guide wear that I’ve seen in my years of experience. I’ve seen bronze guides with 10,000 miles have .010” wear. Most shops never have the opportunity to check this. I’ve seen heads with no oil consumption or any other obvious issues have .010” of guide wear, this is a testament to how good modern valve seals are.
I think that we would all expect that rubber soled shoes, would have better "wear characteristics" than say, paper soled shoes, and the untoward consequences associated with worn shoes, i.e. ripping your feet to pieces, could likely be put off by running a marathon in a good pair of well fitting rubber soled shoes, vs paper soled shoes.
Last edited by '06 Quicksilver Z06; 10-18-2014 at 02:05 AM.
08-29-2013, 11:04 PM
#194
Team Owner
DH
08-30-2013, 10:41 AM
#195
Melting Slicks
Member Since: Jan 2013
Location: what ain't no country I ever heard of
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So do we really know what combination of parts will prevent my ls7 from dropping a valve? I live an hour away from Katech and my z now has 7k miles. I plan on doing heads, cam. But this is just so confusing to me. To op, sorry for your trouble, good to see some progress.
08-30-2013, 11:11 AM
#196
Burning Brakes
So do we really know what combination of parts will prevent my ls7 from dropping a valve? I live an hour away from Katech and my z now has 7k miles. I plan on doing heads, cam. But this is just so confusing to me. To op, sorry for your trouble, good to see some progress.
08-30-2013, 11:31 AM
#197
Melting Slicks
08-30-2013, 12:51 PM
#198
08-30-2013, 01:31 PM
#199
So do we really know what combination of parts will prevent my ls7 from dropping a valve? I live an hour away from Katech and my z now has 7k miles. I plan on doing heads, cam. But this is just so confusing to me. To op, sorry for your trouble, good to see some progress.
Therefore the simplest and cheapest method of prevention is to check and, until a trend is established, periodically monitor the valve guide clearance. The wiggle test is a fine approximation of the clearance that should establish a perfectly usable guideline going forward.
The mechanically-inclined can do the wiggle test themselves. Or you could contact your favorite vendor/mechanic and see if they would be willing to do it for you. In the latter case be sure to get a complete list of measurements (intake and exhaust) to, again, establish a baseline to see if wear presents itself as time goes by.
If you're going to modify the engine then all bets are off and you should consider/evaluate the recommendation of whomever is doing the work, especially if they are warrantying the work. Any significant increase in combustion pressure, combustion temperature, exhaust valve temperature, or exhaust gas temperature can throw the factory design out of balance, possibly requiring change/modification as a result.
.
Last edited by Mark2009; 08-30-2013 at 01:39 PM.
08-30-2013, 01:56 PM
#200
Melting Slicks
Member Since: Jan 2013
Location: what ain't no country I ever heard of
Posts: 2,220
Received 324 Likes
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With a reasonable degree of certainty, a non-worn-out valve guide will prevent it.
Therefore the simplest and cheapest method of prevention is to check and, until a trend is established, periodically monitor the valve guide clearance. The wiggle test is a fine approximation of the clearance that should establish a perfectly usable guideline going forward.
The mechanically-inclined can do the wiggle test themselves. Or you could contact your favorite vendor/mechanic and see if they would be willing to do it for you. In the latter case be sure to get a complete list of measurements (intake and exhaust) to, again, establish a baseline to see if wear presents itself as time goes by.
If you're going to modify the engine then all bets are off and you should consider/evaluate the recommendation of whomever is doing the work, especially if they are warrantying the work. Any significant increase in combustion pressure, combustion temperature, exhaust valve temperature, or exhaust gas temperature can throw the factory design out of balance, possibly requiring change/modification as a result.
.
Therefore the simplest and cheapest method of prevention is to check and, until a trend is established, periodically monitor the valve guide clearance. The wiggle test is a fine approximation of the clearance that should establish a perfectly usable guideline going forward.
The mechanically-inclined can do the wiggle test themselves. Or you could contact your favorite vendor/mechanic and see if they would be willing to do it for you. In the latter case be sure to get a complete list of measurements (intake and exhaust) to, again, establish a baseline to see if wear presents itself as time goes by.
If you're going to modify the engine then all bets are off and you should consider/evaluate the recommendation of whomever is doing the work, especially if they are warrantying the work. Any significant increase in combustion pressure, combustion temperature, exhaust valve temperature, or exhaust gas temperature can throw the factory design out of balance, possibly requiring change/modification as a result.
.