Ls7 heads dropping valves
08-22-2012, 12:11 PM
#21
There was some speculation that the LS7 got the LS9 pump after 2009, but it wasn't the case. The LS7 still gets the same pump that it did in 2006. The crank sprocket changed in 2009 to accommodate the thicker pressure section of the LS9 pump and rather than continuing to make two sprockets they just made the one sprocket go on both engines since it fits on both. A 2009 crank sprocket will fit with a LS7 oil pump, but not the other way around.
To answer the OP, there is nothing wrong with the LS7 exhaust valves. There is a frenzy of people on the Corvette Forum who refuse to accept that conclusion, but we are continuing to use them in racing engines that we have to stand behind and we do not see a problem. We are seeing excessive guide wear (intake and exhaust) on LS7 and LS9 (especially with higher lift camshafts) which we are continuing to gather data on, but we do have a fix that we are doing for any track-going car which is bronze guides and our titanium/molybdenum intake valves.
To answer the OP, there is nothing wrong with the LS7 exhaust valves. There is a frenzy of people on the Corvette Forum who refuse to accept that conclusion, but we are continuing to use them in racing engines that we have to stand behind and we do not see a problem. We are seeing excessive guide wear (intake and exhaust) on LS7 and LS9 (especially with higher lift camshafts) which we are continuing to gather data on, but we do have a fix that we are doing for any track-going car which is bronze guides and our titanium/molybdenum intake valves.
What about the exhaust valves?
08-22-2012, 01:56 PM
#23
There was some speculation that the LS7 got the LS9 pump after 2009, but it wasn't the case. The LS7 still gets the same pump that it did in 2006. The crank sprocket changed in 2009 to accommodate the thicker pressure section of the LS9 pump and rather than continuing to make two sprockets they just made the one sprocket go on both engines since it fits on both. A 2009 crank sprocket will fit with a LS7 oil pump, but not the other way around.
To answer the OP, there is nothing wrong with the LS7 exhaust valves. There is a frenzy of people on the Corvette Forum who refuse to accept that conclusion, but we are continuing to use them in racing engines that we have to stand behind and we do not see a problem. We are seeing excessive guide wear (intake and exhaust) on LS7 and LS9 (especially with higher lift camshafts) which we are continuing to gather data on, but we do have a fix that we are doing for any track-going car which is bronze guides and our titanium/molybdenum intake valves.
To answer the OP, there is nothing wrong with the LS7 exhaust valves. There is a frenzy of people on the Corvette Forum who refuse to accept that conclusion, but we are continuing to use them in racing engines that we have to stand behind and we do not see a problem. We are seeing excessive guide wear (intake and exhaust) on LS7 and LS9 (especially with higher lift camshafts) which we are continuing to gather data on, but we do have a fix that we are doing for any track-going car which is bronze guides and our titanium/molybdenum intake valves.
Come on guys, do you really think a shop that helped with the development of the mighty LS7 will admit to any problems
08-22-2012, 11:23 PM
#24
I have some really nasty miles on a set of stock ls7 heads with stock guides valves and rockers. And I can break anything. The motor in my mustang was describes as the 2nd most beat to **** motor this machine shop as ever seen. Which I took pride in, because I give my stuff hell. And my ls7 is in a 4k lb car with high compression and nitrous
08-23-2012, 09:25 PM
#25
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I would certainly be checking the rocker arm bearings if you are getting a noise. Way more of a problem then the dropped valve syndrome . None the less I replaced the exhaust valves on my ls7 with stainless. And upgraded the rocker trunnions to comps.
08-24-2012, 02:07 PM
#27
To answer the OP, there is nothing wrong with the LS7 exhaust valves. There is a frenzy of people on the Corvette Forum who refuse to accept that conclusion, but we are continuing to use them in racing engines that we have to stand behind and we do not see a problem. We are seeing excessive guide wear (intake and exhaust) on LS7 and LS9 (especially with higher lift camshafts) which we are continuing to gather data on, but we do have a fix that we are doing for any track-going car which is bronze guides and our titanium/molybdenum intake valves.
08-24-2012, 10:29 PM
#29
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I have noticed this. But over on cf, there are a few failures with ss valves. I guess the question now is ; what's causing the excessive guide wear?
08-25-2012, 12:46 AM
#30
08-28-2012, 04:24 PM
#31
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I agree with everything you have said so far. And I like how Katech gives their recommendations for upgrading the heads for "racing". What about the guy I heard in my town that had a ex. valve break on his 2010 z06 after pulling out of his garage? Car had less than 20k miles, bone stock.
I know of a reputable shop here in so-cal that suggests not even getting a tune on a c6 z06, let alone big mods, if you still have a warranty as they don't have much faith in the exhaust valves. And yes I own an 09.
08-28-2012, 07:26 PM
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Most shops hardly see failures compared to the amount they mod. Atleast for street cars.
What shop anyways? One of the biggest shops down in SoCal told me they havent seen a failure on a street car except 1 that had a huge cam, they do agree its the Exhaust Valves but dont see many failures
What shop anyways? One of the biggest shops down in SoCal told me they havent seen a failure on a street car except 1 that had a huge cam, they do agree its the Exhaust Valves but dont see many failures
08-29-2012, 07:09 AM
#33
I agree with everything you have said so far. And I like how Katech gives their recommendations for upgrading the heads for "racing". What about the guy I heard in my town that had a ex. valve break on his 2010 z06 after pulling out of his garage? Car had less than 20k miles, bone stock.
I know of a reputable shop here in so-cal that suggests not even getting a tune on a c6 z06, let alone big mods, if you still have a warranty as they don't have much faith in the exhaust valves. And yes I own an 09.
I know of a reputable shop here in so-cal that suggests not even getting a tune on a c6 z06, let alone big mods, if you still have a warranty as they don't have much faith in the exhaust valves. And yes I own an 09.
08-29-2012, 03:52 PM
#35
Hahahaha, not drinking your coolaid Jason... sorry. Did you see the couple stock valves that were cut open and all the inconsistant wall thickness!?? You said on the CF almost a year ago you guys were checking into this very closely and were going to report back with your findings? What happened there my friend??
08-29-2012, 04:06 PM
#37
Hahahaha, not drinking your coolaid Jason... sorry. Did you see the couple stock valves that were cut open and all the inconsistant wall thickness!?? You said on the CF almost a year ago you guys were checking into this very closely and were going to report back with your findings? What happened there my friend??
No, I didn't see a thread about inconsistent wall thickness but it doesn't concern me. The valves aren't the problem and we know that.
We are still monitoring valve guide wear on as many engines as we can. We have come to the the conclusion that bronze valve guides fixes the problem.
There is nothing wrong with stock rocker arms unless you fall into the small batch problem of 2007 that is well known.
08-29-2012, 10:45 PM
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Does anyone have any info on these? Good, no good, etc? Are PRC Springs good?
https://www.texas-speed.com/p-488-pr...cfm-heads.aspx
https://www.texas-speed.com/p-488-pr...cfm-heads.aspx
09-01-2012, 06:55 PM
#39
Does anyone have any info on these? Good, no good, etc? Are PRC Springs good?
https://www.texas-speed.com/p-488-pr...cfm-heads.aspx
https://www.texas-speed.com/p-488-pr...cfm-heads.aspx
02-17-2013, 10:21 PM
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Why is the guide wear only on the exhaust side?
Service limit is .0037.
What is "high enough to cause breakage"?
.0050? .0100? .0200?
Many people are finding clearance at or above .0100 and no obvious increase in noise.
Service limit is .0037.
What is "high enough to cause breakage"?
.0050? .0100? .0200?
Many people are finding clearance at or above .0100 and no obvious increase in noise.