[Z06] LS7 valve guide news.
05-14-2015, 02:59 PM
#781
Advanced
So what does Darin suggest as a fix for the dropped valve issue. Does he have a go to package. I would like to know what is the best step to fix it. I have an 09Z and yes I fall into the putter around town crowd with an occasional dip into the 7k range. My warranty runs out in July and I am going to do something in the next couple of weeks. Any suggestions.
I'm wondering about the answer to this myself
05-14-2015, 03:25 PM
#782
Soon guys I will post the information, and depo live recording of the whole scenario. Thanks, I know this oiling is restricted from factory heads so u must add some kind of oiling going to guides...soon guys or just pm or call me..
05-14-2015, 03:41 PM
#783
Drifting
05-14-2015, 04:03 PM
#784
05-14-2015, 04:18 PM
#785
Drifting
05-15-2015, 07:16 AM
#786
Burning Brakes
I think this is exactly the thing many needed to see. The "But no one has inspected post failure so how do we know the guides were to blame" is getting a bit silly. Surely if Chad has recorded this many cases we can deduce that there are many more.
Its nothing that I didn't think was going on already but maybe it will help others see it.
Its nothing that I didn't think was going on already but maybe it will help others see it.
EDIT: I found it...Posted July 2012.
This post was on the forum, because this is the video that really changed my mind on a few things.
Last edited by Rock36; 05-15-2015 at 07:19 AM.
05-15-2015, 08:59 AM
#787
Cruising is the passion!
Member Since: Jan 2003
Location: SIMSBURY CT
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St. Jude Donor '07-'08-'09-'10-'11-'12-'13-'14-'15-'16-'17-'18-'19-'20-'21-'22-'23-'24
These 3 heads all dropped a valve on number 7 all 3 heads put a fist size hole in the block one head in a 2010 the other 2011 and an 08. the guides were shot on all exhaust ports, the one that looks like your old engine dropped an exhaust valve then took out the intake valve, the intake valve guide is in spec, when the intake valve broke at 7k rpm it had enough force to cut the valve seat in half and the intake valve head is stuck in the head over and inch deep in the seat, and then going into the bowl. the valve seat was found in the mass air of the vararam cold air. in all 3 heads the guides that dropped valves were all over .0100 these heads all came to me in one day 3 diff ls7's all 3 had a hole in the block, number 7 has been known be be the first cylinder to run lean, i think heat played a huge part in that
05-15-2015, 09:29 AM
#788
Melting Slicks
Actually I think in one of Chad's very first videos, he was demonstrating loose guides in a failed head.
EDIT: I found it...Posted July 2012.
2010 Z06 Dropped Valve - YouTube
This post was on the forum, because this is the video that really changed my mind on a few things.
EDIT: I found it...Posted July 2012.
2010 Z06 Dropped Valve - YouTube
This post was on the forum, because this is the video that really changed my mind on a few things.
Good find, thanks.
Either way, I think everyone knows what to do at this point. Sitting around waiting for your heads to start to make noise or consume oil before taking action would be a huge mistake.
05-15-2015, 09:55 AM
#789
Drifting
I'd be curious as to how non-GM LS7 heads stands up to the valve guide issue? I noticed that Texas Speed now says they make all of their LS heads in house.
I've read one theory where the LS7 heads were potentially all incorrectly machined with unconcentric valve guides, and if a good after market tuner's own machined LS7 heads would exhibit the same problem?
Maybe some good USA made LS7 heads produced on a lower volume by a dedicated cylinder head shop (PRC, WCCH, etc.) would fix that issue? (GM LS7 heads may have been originally cast in Mexico and/or then assembled in Canada at Linamar with arguable attention to detail from what I was reading yesterday on this thread.)
Precision Race Components LS7 CNC 285cc ported cylinder heads.
MADE IN THE USA!!
CAST IN THE USA!!
MACHINED IN THE USA!!
https://www.texas-speed.com/p-488-pr...cfm-heads.aspx
I love the process how they build their heads - much more confidence inspiring than what GM unfortunately took.
Precision Race Components – SEE Why We Build Superior Cylinder Heads!
http://www.texas-speed.com/t-prcheads.aspx
I've read one theory where the LS7 heads were potentially all incorrectly machined with unconcentric valve guides, and if a good after market tuner's own machined LS7 heads would exhibit the same problem?
Maybe some good USA made LS7 heads produced on a lower volume by a dedicated cylinder head shop (PRC, WCCH, etc.) would fix that issue? (GM LS7 heads may have been originally cast in Mexico and/or then assembled in Canada at Linamar with arguable attention to detail from what I was reading yesterday on this thread.)
Precision Race Components LS7 CNC 285cc ported cylinder heads.
MADE IN THE USA!!
CAST IN THE USA!!
MACHINED IN THE USA!!
https://www.texas-speed.com/p-488-pr...cfm-heads.aspx
I love the process how they build their heads - much more confidence inspiring than what GM unfortunately took.
Precision Race Components – SEE Why We Build Superior Cylinder Heads!
http://www.texas-speed.com/t-prcheads.aspx
Last edited by BigVette427; 05-15-2015 at 10:00 AM.
05-15-2015, 10:41 AM
#790
If you own the car, you have the problem....It's just a matter of time..Do you feel lucky...hahahah....The fix is simple.....replace the GM exhaust valve, guides, and move on.......
05-15-2015, 11:37 AM
#792
Only disadvantage is I'd no longer have a numbers matching car. Which may or may not affect it's future value.
05-15-2015, 12:03 PM
#793
Burning Brakes
I posted about this a few pages back. I think closed loop driving conditions are causeing a lot of heat, from just putting around town. I let a friend of mine drive my z last summer hot as hell here in fl. he took off in 3rd gear thinking it was first, sounded like valves rattling from bad gas which is detonation, my car i spend weeks tuning in right. as i have a wideband installed and i can plug it into my laptop when using hp tuners. never the less my heads were out of spec and i was running a mild tune, I think this is adding to the problem even on stock cars I've seen more worn out guides in cars that never see redline than cars that do. older guy came here a few weeks ago for a wiggle test, 25k miles 07 guy got the car new. the guy said he got on it one time to 7k , siad the car scared him and he just uses it for a weekend driver for him an his wife..guide were shot. I just don't know for sure but it has had me thinking about it for a few years now. and you are right the exhaust valve in all cases i've seen the exhaust valve is wearing from the bottom up,"HEAT" the intake wears from the top. I've seen heads that when you take the valve seal off the guide to see a rainbow effect on the guide, this is heat as for the intake I think its the coating on the ti intake valve is to rough. but i'm not sure on any of it these are just guesses at this point
I know you said you were running LS3 heads now, so I was wondering why you didn't try one of the other LS7 aftermarket heads. If it is partly a heat issue, have you checked the guides on your LS3 heads to see if they are wearing any faster?
Last edited by Rock36; 05-15-2015 at 12:06 PM.
05-15-2015, 12:28 PM
#794
Melting Slicks
Member Since: Nov 2002
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I would like to know this as well. If I had a reasonable assurance that something like a PRC head would eliminate this potential issue, I would already have new heads on the way and call it a day. I guess there is no telling any of it however until people put some real mileage on these aftermarket heads. I would have to think it would solve the issue though...
05-15-2015, 02:43 PM
#795
Pro
Also, there was a set of PRC heads with worn out guides, a year or so ago, as well. Not saying those heads will all do that, but there has been one set so far.
05-15-2015, 04:08 PM
#796
Burning Brakes
One thing that makes ls7 different than many other gm v8s is the dry sump oiling system of the 06 - 11 (non Z07) Z06s. If you recall, the 2012 up cars have a zr1 style liquid oil cooler which heat the oil faster. The air to air cooled 6-10s take 20 min for the oil to warm up to 100 degrees sometimes. Maybe less if you live in a warm climate. Anyway, the guides wear down without oil, and then the oil comes when it heats up and starts the sand papering. Just a theory, but I have yet to see guide wear in a 2012up car.
One more thing, Chad, for every person that insults you on the forum, there are 10 like me who would like to buy you a beer and shake your hand. We just don't post. I figured I'd post up a dumb idea so people can attack me ( a nobody waxer who's guides were shot at 14k miles ) and let the pros figure this out.
One more thing, Chad, for every person that insults you on the forum, there are 10 like me who would like to buy you a beer and shake your hand. We just don't post. I figured I'd post up a dumb idea so people can attack me ( a nobody waxer who's guides were shot at 14k miles ) and let the pros figure this out.
Last edited by rockinSeat; 05-15-2015 at 04:15 PM. Reason: pike should be like
05-15-2015, 04:41 PM
#797
Melting Slicks
Unless you're in my position and still have a lot of the PT warranty left. If mine blows, GM pays for the roadside assistance and $20K+ for a swap along with repairing any collateral damage. That'll teach em!
Only disadvantage is I'd no longer have a numbers matching car. Which may or may not affect it's future value.
Only disadvantage is I'd no longer have a numbers matching car. Which may or may not affect it's future value.
It wont affect the value at all. These cars aren't collectibles. No one would ever check. The only thing that could possibly count against the value is the service history showing "Engine Replaced". But most potential buyers see that as a plus.
I agree though, if you are under warranty, drive the **** out of it and don't worry at all. Stick it to em if it blows up.
05-15-2015, 05:19 PM
#798
Burning Brakes
One thing that makes ls7 different than many other gm v8s is the dry sump oiling system of the 06 - 11 (non Z07) Z06s. If you recall, the 2012 up cars have a zr1 style liquid oil cooler which heat the oil faster. The air to air cooled 6-10s take 20 min for the oil to warm up to 100 degrees sometimes. Maybe less if you live in a warm climate. Anyway, the guides wear down without oil, and then the oil comes when it heats up and starts the sand papering. Just a theory, but I have yet to see guide wear in a 2012up car.
One more thing, Chad, for every person that insults you on the forum, there are 10 like me who would like to buy you a beer and shake your hand. We just don't post. I figured I'd post up a dumb idea so people can attack me ( a nobody waxer who's guides were shot at 14k miles ) and let the pros figure this out.
One more thing, Chad, for every person that insults you on the forum, there are 10 like me who would like to buy you a beer and shake your hand. We just don't post. I figured I'd post up a dumb idea so people can attack me ( a nobody waxer who's guides were shot at 14k miles ) and let the pros figure this out.
There are a few worn guides on 2012s 2013s and 427 verts in this thread.
05-15-2015, 07:02 PM
#799
Burning Brakes
Yes I have I was running all pro heads on my car with jesel rockers, i've seen prc stock reworked casting out of spec i've seen 2 sets of livernois heads out of spec after reworked, aslo 2 from lingenfelter reworked stock castings out of spec. for this reason i'n using ls3 heads now...I have 500 miles on them at this point but in about 6 months I will be checking these or every 5k miles so maybe sooner.
05-15-2015, 07:15 PM
#800
Burning Brakes
https://www.corvetteforum.com/forums...-registry.html
There are a few worn guides on 2012s 2013s and 427 verts in this thread.
There are a few worn guides on 2012s 2013s and 427 verts in this thread.
In this thread, both sides are right of course, yes the wiggle test yields false positives for out of spec guides, but out-of spec guides are causing dropped exhaust valves.
Have any 2012 or 2013s dropped valves? Were they exhaust or intake?