[Z06] LS7 Head causes of valve guide wear
11-17-2013, 11:42 AM
#1
Drifting
Thread Starter
LS7 Head causes of valve guide wear
I never thought I'd start a thread on the topic of valve guide wear but wanted to confirm my understanding of the causes and what issues could still remain even after reworking the heads.
I have 2 more years on the GMPP but after reading NavyAirTraffic's results in his/her thread I'm on the fence now.
Please add or correct my understanding.
1. GM supposedly confirmed there has been a machining issue with their head supplier which has been contained since 2011. No details of the type or types of machining issue(s).
2. GM issued TSB-13-06-01-001 on how dealers are to handle customer's concerns on valve guide wear.
3. One of the types of machining issue was the valve seat to valve guide angle were off causing the valve to wear the guides since it does not seat perfectly.
4. CF member "john_g_46" identified the rockers were exerting side force due to the rocker pedestal and/or rocker not machined/designed correctly. He showed how you can determine if the rocker is riding on the stem.
5. There have been some first and second hand comments from WCCH, Katech, and Lingenfelter that indicates the LS7 does have excessive guide wear.
My concern is if the head is machined to correct the guide angle, that solves one of the machining issues, but what about #4 above regarding the excessive side force that would cause guide wear?
I have 2 more years on the GMPP but after reading NavyAirTraffic's results in his/her thread I'm on the fence now.
Please add or correct my understanding.
1. GM supposedly confirmed there has been a machining issue with their head supplier which has been contained since 2011. No details of the type or types of machining issue(s).
2. GM issued TSB-13-06-01-001 on how dealers are to handle customer's concerns on valve guide wear.
3. One of the types of machining issue was the valve seat to valve guide angle were off causing the valve to wear the guides since it does not seat perfectly.
4. CF member "john_g_46" identified the rockers were exerting side force due to the rocker pedestal and/or rocker not machined/designed correctly. He showed how you can determine if the rocker is riding on the stem.
5. There have been some first and second hand comments from WCCH, Katech, and Lingenfelter that indicates the LS7 does have excessive guide wear.
My concern is if the head is machined to correct the guide angle, that solves one of the machining issues, but what about #4 above regarding the excessive side force that would cause guide wear?
11-17-2013, 12:38 PM
#2
I never thought I'd start a thread on the topic of valve guide wear but wanted to confirm my understanding of the causes and what issues could still remain even after reworking the heads.
I have 2 more years on the GMPP but after reading NavyAirTraffic's results in his/her thread I'm on the fence now.
Please add or correct my understanding.
1. GM supposedly confirmed there has been a machining issue with their head supplier which has been contained since 2011. No details of the type or types of machining issue(s).
2. GM issued TSB-13-06-01-001 on how dealers are to handle customer's concerns on valve guide wear.
3. One of the types of machining issue was the valve seat to valve guide angle were off causing the valve to wear the guides since it does not seat perfectly.
4. CF member "john_g_46" identified the rockers were exerting side force due to the rocker pedestal and/or rocker not machined/designed correctly. He showed how you can determine if the rocker is riding on the stem.
5. There have been some first and second hand comments from WCCH, Katech, and Lingenfelter that indicates the LS7 does have excessive guide wear.
My concern is if the head is machined to correct the guide angle, that solves one of the machining issues, but what about #4 above regarding the excessive side force that would cause guide wear?
I have 2 more years on the GMPP but after reading NavyAirTraffic's results in his/her thread I'm on the fence now.
Please add or correct my understanding.
1. GM supposedly confirmed there has been a machining issue with their head supplier which has been contained since 2011. No details of the type or types of machining issue(s).
2. GM issued TSB-13-06-01-001 on how dealers are to handle customer's concerns on valve guide wear.
3. One of the types of machining issue was the valve seat to valve guide angle were off causing the valve to wear the guides since it does not seat perfectly.
4. CF member "john_g_46" identified the rockers were exerting side force due to the rocker pedestal and/or rocker not machined/designed correctly. He showed how you can determine if the rocker is riding on the stem.
5. There have been some first and second hand comments from WCCH, Katech, and Lingenfelter that indicates the LS7 does have excessive guide wear.
My concern is if the head is machined to correct the guide angle, that solves one of the machining issues, but what about #4 above regarding the excessive side force that would cause guide wear?
Good luck.
11-17-2013, 05:18 PM
#7
I never thought I'd start a thread on the topic of valve guide wear but wanted to confirm my understanding of the causes and what issues could still remain even after reworking the heads.
I have 2 more years on the GMPP but after reading NavyAirTraffic's results in his/her thread I'm on the fence now.
Please add or correct my understanding.
1. GM supposedly confirmed there has been a machining issue with their head supplier which has been contained since 2011. No details of the type or types of machining issue(s).
I have 2 more years on the GMPP but after reading NavyAirTraffic's results in his/her thread I'm on the fence now.
Please add or correct my understanding.
1. GM supposedly confirmed there has been a machining issue with their head supplier which has been contained since 2011. No details of the type or types of machining issue(s).
3. One of the types of machining issue was the valve seat to valve guide angle were off causing the valve to wear the guides since it does not seat perfectly.
4. CF member "john_g_46" identified the rockers were exerting side force due to the rocker pedestal and/or rocker not machined/designed correctly. He showed how you can determine if the rocker is riding on the stem.
5. There have been some first and second hand comments from WCCH, Katech, and Lingenfelter that indicates the LS7 does have excessive guide wear.
My concern is if the head is machined to correct the guide angle, that solves one of the machining issues, but what about #4 above regarding the excessive side force that would cause guide wear?
As to contacting a "cylinder head professional", contact four of them on this issue and you'll probably get three different opinions. Then all you'll need is a three-headed coin
I recently ran across an interesting post by an engine builder on another forum... he was seeing core shift in the new aluminum heads of a BBC (big block Chevy) after a few engine dyno pulls, to the point that the previously well-machined heads were exhibiting excessive seat-guide concentricity after a few heat cycles from new (which of course then kills the valve guides). His solution was to heat cycle new castings (in an oven) to allow them to 'take a set' before machining them to spec. He reported that this solved the core shift problem w/new heads.
11-17-2013, 05:41 PM
#8
Safety Car
Given that you have two more years of GMPP you might not care what the problem is as your protection is not correction but repair on GMPPs dime.
I also see two ways to approach that situation. Get the "wiggle test" done by a competent dealer and than have them spend a couple of thousand dollars to fix it if not in spec. Your cost $3-400 if the guides are in spec.
Or not do a "wiggle test" and let them spend $15-19,000 to fix it when/if it breaks.
My wiggle test is scheduled next Mon/Tues at Abel Chevrolet along with a couple of small warranty issues (P0420 reflash) and Rocking Seat repair.
We all get to make our own choices up if we have a warranty.
Those without a warranty can self insure (do nothing and hope all this is not really happening) or get the heads redone to whatever specs they want to pay for.
It is really not difficult to figure out what to do. You just need to think about it a bit and then make your decision.
I also see two ways to approach that situation. Get the "wiggle test" done by a competent dealer and than have them spend a couple of thousand dollars to fix it if not in spec. Your cost $3-400 if the guides are in spec.
Or not do a "wiggle test" and let them spend $15-19,000 to fix it when/if it breaks.
My wiggle test is scheduled next Mon/Tues at Abel Chevrolet along with a couple of small warranty issues (P0420 reflash) and Rocking Seat repair.
We all get to make our own choices up if we have a warranty.
Those without a warranty can self insure (do nothing and hope all this is not really happening) or get the heads redone to whatever specs they want to pay for.
It is really not difficult to figure out what to do. You just need to think about it a bit and then make your decision.
Last edited by pkincy; 11-17-2013 at 05:43 PM.
11-18-2013, 10:45 AM
#11
Safety Car
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I recently ran across an interesting post by an engine builder on another forum... he was seeing core shift in the new aluminum heads of a BBC (big block Chevy) after a few engine dyno pulls, to the point that the previously well-machined heads were exhibiting excessive seat-guide concentricity after a few heat cycles from new (which of course then kills the valve guides). His solution was to heat cycle new castings (in an oven) to allow them to 'take a set' before machining them to spec. He reported that this solved the core shift problem w/new heads.
Last edited by BearZ06; 11-18-2013 at 11:42 AM.
11-18-2013, 10:54 AM
#12
I never thought I'd start a thread on the topic of valve guide wear but wanted to confirm my understanding of the causes and what issues could still remain even after reworking the heads.
I have 2 more years on the GMPP but after reading NavyAirTraffic's results in his/her thread I'm on the fence now.
Please add or correct my understanding.
1. GM supposedly confirmed there has been a machining issue with their head supplier which has been contained since 2011. No details of the type or types of machining issue(s).
2. GM issued TSB-13-06-01-001 on how dealers are to handle customer's concerns on valve guide wear.
3. One of the types of machining issue was the valve seat to valve guide angle were off causing the valve to wear the guides since it does not seat perfectly.
4. CF member "john_g_46" identified the rockers were exerting side force due to the rocker pedestal and/or rocker not machined/designed correctly. He showed how you can determine if the rocker is riding on the stem.
5. There have been some first and second hand comments from WCCH, Katech, and Lingenfelter that indicates the LS7 does have excessive guide wear.
My concern is if the head is machined to correct the guide angle, that solves one of the machining issues, but what about #4 above regarding the excessive side force that would cause guide wear?
I have 2 more years on the GMPP but after reading NavyAirTraffic's results in his/her thread I'm on the fence now.
Please add or correct my understanding.
1. GM supposedly confirmed there has been a machining issue with their head supplier which has been contained since 2011. No details of the type or types of machining issue(s).
2. GM issued TSB-13-06-01-001 on how dealers are to handle customer's concerns on valve guide wear.
3. One of the types of machining issue was the valve seat to valve guide angle were off causing the valve to wear the guides since it does not seat perfectly.
4. CF member "john_g_46" identified the rockers were exerting side force due to the rocker pedestal and/or rocker not machined/designed correctly. He showed how you can determine if the rocker is riding on the stem.
5. There have been some first and second hand comments from WCCH, Katech, and Lingenfelter that indicates the LS7 does have excessive guide wear.
My concern is if the head is machined to correct the guide angle, that solves one of the machining issues, but what about #4 above regarding the excessive side force that would cause guide wear?
All good stuff to ponder, but it can make you nuts if you think too much about it. I have 18 month of warranty, so I'm not stressing out, but I'm researching as much as I can. Talk about looking into a bunch of unknowns. If installing new guides/valves is the answer, I called several local shops and dealerships to ask how much they would charge to swap heads. After I got a price quote, I specifically asked each place if they had removed/reinstalled heads on an LS7 before. Not a single place I called has ever removed a head on an LS7. I'll take that as a good sign.
I'm in NW OH, where most Z06s get driven about 5-6K miles a year. Maybe all of them around here a just too low in miles to have any issues yet? I split my summer between my bike and my car, so when my warrany is up I probably wont have 15K miles on the Z06.
Its safe to say the vast majority of posts Ive found of blown engines have seen some hard use. I agree, this car was built for hard use, and it should take it, but I'm assuming most cars blown up on the track dont get much help in terms or warranty. I watched a video a while back of a guy with a head removed and a busted valve from his 2010. My first thought was, if its under warranty, why isnt it at the dealer being replaced under warranty?
I think the more important question, which should most concern potential buyers and current owners is how is GM handling it under warranty, and out of warranty? If there is a list of 25 blown engines, how many of those were replaced under warranty? If some of those destroyed are low miles, but beyond the 5 yrs, how has GM handled those?
I love my z06, and I enjoy the hell out of it, even though I'm a boring guy who will never make a lap around a racetrack. I'm not worried today, but in 19 months, I'm going to be concerned. A lot can happen in 18 months. Maybe we'll see a GM recall, a class action law suit, or maybe it was just a bad batch of heads and those which have already broke are all that were going to break...
Thanks for the forum guys. Been reading posts for a couple years, before I registered.