[Z06] Question about the valve drop issue some of the LS7 motors are having
10-27-2011, 11:00 PM
#21
Melting Slicks
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I bet some of you guys don't realize that LS7 Heads come Cnd'd ported from the factory, really not a lot to gain there, but milling the heads is the winning ticket to extract that little extra horsepower (lying within those very high performing/flowing stock LS7 heads). 
Mill the heads to make around 11:8 to compression to hit that 600rwhp mark (with aftermarket cam of course), and do all the other basic stuff that Jason at Katech recommonds if one wants to safe- guard against the dropping valve issue.
1. Bronze Valve Guides.
2. Valve Job
3. Stock TI vales unless your building a real CRAZY high HP motor or a racing engine (625+rhwp) then use Inconel (sp?) valves.
4. If using stock cam STICK with new OEM springs and STOCK rockers. Of course upgrade to proper sping and pushrod if she is cammed up.
!
Mill the heads to make around 11:8 to compression to hit that 600rwhp mark (with aftermarket cam of course), and do all the other basic stuff that Jason at Katech recommonds if one wants to safe- guard against the dropping valve issue.
1. Bronze Valve Guides.
2. Valve Job
3. Stock TI vales unless your building a real CRAZY high HP motor or a racing engine (625+rhwp) then use Inconel (sp?) valves.
4. If using stock cam STICK with new OEM springs and STOCK rockers. Of course upgrade to proper sping and pushrod if she is cammed up.
!I am aiming for about 525-550 RWHP once I am done with the vehicle, so no mention of replacing the valves came up. I should be fine in that department hopefully.
10-27-2011, 11:17 PM
#22
Safety Car
I bet some of you guys don't realize that LS7 Heads come Cnd'd ported from the factory, really not a lot to gain there, but milling the heads is the winning ticket to extract that little extra horsepower (lying within those very high performing/flowing stock LS7 heads).
Mill the heads to make around 11:8 to compression to hit that 600rwhp mark (with aftermarket cam of course), and do all the other basic stuff that Jason at Katech recommonds if one wants to safe- guard against the dropping valve issue.
1. Bronze Valve Guides.
2. Valve Job
3. Stock TI vales unless your building a real CRAZY high HP motor or a racing engine (625+rhwp) then use Inconel (sp?) valves.
4. If using stock cam STICK with new OEM springs and STOCK rockers. Of course upgrade to proper sping and pushrod if she is cammed up.!
Mill the heads to make around 11:8 to compression to hit that 600rwhp mark (with aftermarket cam of course), and do all the other basic stuff that Jason at Katech recommonds if one wants to safe- guard against the dropping valve issue.
1. Bronze Valve Guides.
2. Valve Job
3. Stock TI vales unless your building a real CRAZY high HP motor or a racing engine (625+rhwp) then use Inconel (sp?) valves.
4. If using stock cam STICK with new OEM springs and STOCK rockers. Of course upgrade to proper sping and pushrod if she is cammed up.
!But I'm curious why you say use stock springs? They both said it wouldn't hurt running springs good until 660lift or whatever Patriot Golds are good until I dont remember.
WCCH also said it'd be a good idea for extra security to do his Rocker mod to the stockers
10-27-2011, 11:19 PM
#23
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St. Jude Donor '06
NO, the common consensus even among most of the biggest shops who have rendered some info on this issue, is that is that there is nothing wrong with any portion of the stock rocker arms on the LS7 heads. That is pretty much common knowledge among all these threads.
Yes, 3 angle valve job, NO, regarding messing with any portion of the rocker arms.
Do yourself a favor, call KATECH, ask for Jason, tell him what that you want to take precautions and WANT to do some things to safeguard against the valve dropping scare, and take his advice 100%. He builds engines for GM racing and many other racing vettes, and that is where I am getting MOST of my info from.
If Katech told you/tells you something different follow their lead 100% on all issues sourrounding this topic.
Yes, 3 angle valve job, NO, regarding messing with any portion of the rocker arms.
Do yourself a favor, call KATECH, ask for Jason, tell him what that you want to take precautions and WANT to do some things to safeguard against the valve dropping scare, and take his advice 100%. He builds engines for GM racing and many other racing vettes, and that is where I am getting MOST of my info from.
If Katech told you/tells you something different follow their lead 100% on all issues sourrounding this topic.
Last edited by Mopar Jimmy; 10-27-2011 at 11:25 PM.
10-27-2011, 11:24 PM
#24
Safety Car
Katech get his Heads from WCCH so I figured I'd call the owner of WCCH Richard, he seem to know alot about the issues LS7s have had with the valves/guides.
But I will prolly give Jason a call tomorrow just to get his opinion as well, expensive stuff to mess up on
But I will prolly give Jason a call tomorrow just to get his opinion as well, expensive stuff to mess up on
10-27-2011, 11:30 PM
#25
Safety Car
I started to put SS valves but went back and changed it to read upgraded because I haven't seen research to back SS valves. Honestly my opinion is that the valve job, bronze guides, and "new" or at least undamaged valves would suffice.
10-27-2011, 11:37 PM
#26
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St. Jude Donor '06
That being said the reasoning with staying with NEW stock springs on a STOCK LS7 cam is rather simple. If you go with an aftermaret double spring which are made for aftermarket cams, those springs have more spring pressure than the stockers and are of course heavier, and you throw off the awesome lightweight valvetrain geometry of the stock LS7 engine. These cars DO NOT HAVE valve spring issues (when the cam is not touched and the springs are in good shape or new of course).
Going to a double spring is essentially OVERKILL for the STOCK LS7 cam application and may very well overtax your valvetrain, and will throw off the great lightweight valvetrain stock design, causing you more problems then if you just run the stockers. That is what my research has shown over the last 8 years since dealing with the stock TI valves in both C6 Z and C5 Zs.
That being said if I were you I would do what JASON at KATECH says to do. However, you don't need ALL THE BELLS AND WHISTLES that WCCH offers when your running a STOCK CAM!!!!!!! Make sure you tell them EXACTY what cam your running and how you will be using the car (road racing, drag racing, Sunday cruises, etc.).
Best of luck, keep us posted what the EXPERTS tell you to do and what you do!!
Last edited by Mopar Jimmy; 10-27-2011 at 11:57 PM.
10-27-2011, 11:44 PM
#27
Safety Car
Thanks Jimmy, Ya I will hit up Jason tomorrow.
Only reason I'd go with upgraded springs is I may or may not do a cam upgrade in the future so figured I'd save myself future install $ and do the springs now since they said it wouldn't hurt but I will double check now that you mention it. This is just my Daily Driver/Only car it will never see a road course, and maybe once a year see the drag strip. Mainly just going to be a highway terror if someone wants to play
Only reason I'd go with upgraded springs is I may or may not do a cam upgrade in the future so figured I'd save myself future install $ and do the springs now since they said it wouldn't hurt but I will double check now that you mention it. This is just my Daily Driver/Only car it will never see a road course, and maybe once a year see the drag strip. Mainly just going to be a highway terror if someone wants to play
10-28-2011, 12:48 AM
#28
The "Search" feature on this sight is your friend best of luck, you have many, many hours on this very subject you can read up on right at your disposal on this forum.
Because these threads are becoming WAY to repetitive and redundant and I am tired of repeating myself, that is the best advice I can give you.
Oh yeah, the bad news is after reading about 100 hours on this topic you will find out there is no definitive answer to your question!
Because these threads are becoming WAY to repetitive and redundant and I am tired of repeating myself, that is the best advice I can give you.
Oh yeah, the bad news is after reading about 100 hours on this topic you will find out there is no definitive answer to your question!
10-28-2011, 12:57 AM
#29
NO, the common consensus even among most of the biggest shops who have rendered some info on this issue, is that is that there is nothing wrong with any portion of the stock rocker arms on the LS7 heads. That is pretty much common knowledge among all these threads.
Yes, 3 angle valve job, NO, regarding messing with any portion of the rocker arms.
Do yourself a favor, call KATECH, ask for Jason, tell him what that you want to take precautions and WANT to do some things to safeguard against the valve dropping scare, and take his advice 100%. He builds engines for GM racing and many other racing vettes, and that is where I am getting MOST of my info from.
If Katech told you/tells you something different follow their lead 100% on all issues sourrounding this topic.
Yes, 3 angle valve job, NO, regarding messing with any portion of the rocker arms.
Do yourself a favor, call KATECH, ask for Jason, tell him what that you want to take precautions and WANT to do some things to safeguard against the valve dropping scare, and take his advice 100%. He builds engines for GM racing and many other racing vettes, and that is where I am getting MOST of my info from.
If Katech told you/tells you something different follow their lead 100% on all issues sourrounding this topic.
10-28-2011, 02:15 PM
#31
Drifting
I just went with a comp cams 231 247 cam in my 06z. while doing the cam I got spooked by all the threads about the valve problems. I decided to pull the heads and change the guides to be safe. while the heads were off I had .040 shaved off to bump comp for a little more power. I also had the heads ported. while the work was being done the machine shop calls and says the guides were bad and the exhaust valves were shot and needed to be replaced due to excessive wear. this very well may have saved my motor. if you are doing a cam I would do the heads as well. you will get more power and you may prevent a failure at the same time.
Mark
10-28-2011, 02:31 PM
#32
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St. Jude Donor '06
Hey jimmy, whats up? hope all is well. On the rocker arms, wouldnt you think it would be a good idea to atleast do the trunion bearing upgrade? along with the other things we have learned, such as valves, guides and springs just to be sure. its a bit more$$ but thats what i would do anyway just to take out the gremlins. whats your feeling?
I would simply follow the lead of what the expert LS7 head shop told me to do, like WCCH, after I cross examined him 5 times
, after telling him exactly what my goals, objectives and use of my Z would be for, and what type of power I was planning to make.
10-28-2011, 04:56 PM
#34
Why do people keep saying call Katech? Interesting Katech is directing people to WCCH. For the longest time Katech said that they never saw the guide problem. Now they are saying they are starting to see it. Doesn't seem like they know much about it and people keep acting like Katech knows it all. Well if they do then why not put out the exact problem and fix? Not meaning this as an attack on Katech but truely don't understand this.
10-28-2011, 10:42 PM
#36
Le Mans Master
yea. I did a search for a good two hours yesterday and solutions vary from trunions to replacing the rockers to replacing the guides.
at minimum, I am replacing the springs and pushrods. I noticed yesterday that some members were recommending changing out the valves while other members did not agree with the idea.
Some other input from others would be much appreciated on the topic.
at minimum, I am replacing the springs and pushrods. I noticed yesterday that some members were recommending changing out the valves while other members did not agree with the idea.
Some other input from others would be much appreciated on the topic.
10-29-2011, 04:17 AM
#37
Racer
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10-29-2011, 06:45 AM
#38
Great point, there is an issue for sure. I for one cannot believe people are blaming everything but design, there is a root cause issue and GM is not fixing it as we have seen the problem continue. IMO they will ride out the problem until warranty is over and be done with it, engine will not be made much longer, just dollars.
10-29-2011, 10:01 AM
#39
Race Director
The "Search" feature on this sight is your friend best of luck, you have many, many hours on this very subject you can read up on right at your disposal on this forum.
Because these threads are becoming WAY to repetitive and redundant and I am tired of repeating myself, that is the best advice I can give you.
Oh yeah, the bad news is after reading about 100 hours on this topic you will find out there is no definitive answer to your question!
Because these threads are becoming WAY to repetitive and redundant and I am tired of repeating myself, that is the best advice I can give you.
Oh yeah, the bad news is after reading about 100 hours on this topic you will find out there is no definitive answer to your question!
yup... just a bunch of speculation and the only thing anyone knows is the exhaust valve seems to be a weak link of the motor. Thats it.
10-29-2011, 10:29 AM
#40
There seams to be alot of misconception as far as a 3 valve job is concern. To located the center margine of a valve seat three angles need to be cut, thus the three angle valve job. Don't be paying for something that needs to performed to properly do the valve job. Makes me laugh when guys get quoted for a three angle job when its a normal practice on all valve jobs to begin with. I believe the issue lies it the side load the valve is under, compile this with heat soak and thus excessive wear occurs. With such a large lift and rocker ratio, full roller rocker would relive if not completely remedie the problem. Bronze guides still wear it a softer metal, but its better on the valves less chances of gauling , thus again less wear. Cast guides aren't bad but conditions within the valve train must be ideal to prevent excessive wear. And as we all know that's not the case with the ls7, its a monster engine. I would be interested in hearing from someone running stock guides with full rollers, and see their findings, bet it would be good.