[Z06] GM replacement heads
04-15-2015, 01:17 AM
#41
Race Director
The guides in the warranty replacement heads were not the problem.
The replacement heads had a number of valve seats with excessive runout. Rather than wait for a second set of replacement heads, because time was of the essence due to the car in question being the Lead Car for the 2014 National Corvette Caravan out of California 10 days later, I ordered my cylinder head service to repair them. Because of the circumstances my repair of the replacement heads was covered under warranty.
It is true that Linimar was not holding the required tolerance for seat runout on a consistent basis, however, it is a distortion of fact to say:
The replacement heads had a number of valve seats with excessive runout. Rather than wait for a second set of replacement heads, because time was of the essence due to the car in question being the Lead Car for the 2014 National Corvette Caravan out of California 10 days later, I ordered my cylinder head service to repair them. Because of the circumstances my repair of the replacement heads was covered under warranty.
It is true that Linimar was not holding the required tolerance for seat runout on a consistent basis, however, it is a distortion of fact to say:
Hib, I value your input but I just don't understand how GM can say there is 100% inspection and continue to have Linemar provide out of spec heads.
Then they reward Linemar with a contract for C7 Z06 e-difs and Linemar fails to properly fill the dif with fluid and having 1000's of them underfilled, PDI doesn't pick it up and a guy from CA picks up his car at the NCM and only gets to TX before being stranded with a failed dif.
04-15-2015, 01:47 AM
#42
After watching these videos as I suspected bronze guides is not a fix for our heads. So my question is, the head design for the ls7 must be causing this issue, if heads are being reworked by vendors and properly being assembled correctly something is definitely wrong with the design.
04-15-2015, 09:09 AM
#43
After watching these videos as I suspected bronze guides is not a fix for our heads. So my question is, the head design for the ls7 must be causing this issue, if heads are being reworked by vendors and properly being assembled correctly something is definitely wrong with the design.
04-15-2015, 01:04 PM
#44
I'm on my 3 set of heads and done a different guide each time and right now on my other set being done by Darin Morgan. So we can all argue and speculate and so on and measure all we want? What's the cause still there's no answer..like I said before on tests almost immediately less than 1000 miles guides get shot instantly. Now I have not tried a mast head or other brand but all ls7 heads, last head was off 10-11 z06 less than 7k miles shot. So my opinion is no head Is good from gm. Yes my first set went 64k but were out of spec... So what's next to do.
04-15-2015, 02:14 PM
#45
Team Owner
I'm on my 3 set of heads and done a different guide each time and right now on my other set being done by Darin Morgan. So we can all argue and speculate and so on and measure all we want? What's the cause still there's no answer..like I said before on tests almost immediately less than 1000 miles guides get shot instantly. Now I have not tried a mast head or other brand but all ls7 heads, last head was off 10-11 z06 less than 7k miles shot. So my opinion is no head Is good from gm. Yes my first set went 64k but were out of spec... So what's next to do.
04-15-2015, 03:15 PM
#46
I'm on my 3 set of heads and done a different guide each time and right now on my other set being done by Darin Morgan. So we can all argue and speculate and so on and measure all we want? What's the cause still there's no answer..like I said before on tests almost immediately less than 1000 miles guides get shot instantly. Now I have not tried a mast head or other brand but all ls7 heads, last head was off 10-11 z06 less than 7k miles shot. So my opinion is no head Is good from gm. Yes my first set went 64k but were out of spec... So what's next to do.
For example, if the guides with excessive clearance are within spec at the bottom (valve seat end), but are showing excessive clearance at the top (rocker end), then you know that the valve has been side loaded by the rocker. Now look again at your map. Is the wear uniform? – this will be very unlikely. Is the wear in the direction from the front of the engine to the back? Or, is it in the direction across the head from intake to exhaust? Knowing this will tell you how the rocker was loading the valve stem. Normally, you’ll see it in the intake to exhaust direction, and that will tell you that you either have too much lift for the OE rocker, or there was too much friction from impropper tip or rocker pad finish, or a combination of both. You can at this point decide if you would rather run less lift, or move to a roller tipped rocker.
If the wear is at the bottom of the guide (seat end), then you know you have a seat to guide concentricity issue.
If wear is in an hour glass shape, which end has more wear? Again, that will tell you where the problem originated from. If it is equal at the top and bottom, then the guide clearance was too much after initial machine work was done.
So really, without thoroughly mapping the wear with precision instruments, you should not make assumptions and just change worn components, because you may not be addressing the problem that caused the wear.
If you have wear from rocker loading, it doesn’t matter what type of guild you go with, or cylinder head manufacture. The same problem will happen again, unless you do something to fix the rocker loading issue.
04-15-2015, 07:18 PM
#48
All heads were done by Darin. Still going 17k on these. Just different guides, matching cam. Ferrea valves this time. Current has the rev.
Last edited by RamAir972003; 04-15-2015 at 07:58 PM.
04-15-2015, 07:55 PM
#49
Well…..before you do any work to the heads, you (or someone you trust) must first disassemble the heads and clean them thoroughly, making sure to mark each valve and spring assembly in a way that you know where they were in the heads. Then you measure the guide bores with a small hole dial bore gauge. I prefer a pin type bore gauge, as I can map the entire bore and jot down direction of wear and taper. After you have this data for all guides, you will have data to apply logic to.
For example, if the guides with excessive clearance are within spec at the bottom (valve seat end), but are showing excessive clearance at the top (rocker end), then you know that the valve has been side loaded by the rocker. Now look again at your map. Is the wear uniform? – this will be very unlikely. Is the wear in the direction from the front of the engine to the back? Or, is it in the direction across the head from intake to exhaust? Knowing this will tell you how the rocker was loading the valve stem. Normally, you’ll see it in the intake to exhaust direction, and that will tell you that you either have too much lift for the OE rocker, or there was too much friction from impropper tip or rocker pad finish, or a combination of both. You can at this point decide if you would rather run less lift, or move to a roller tipped rocker.
If the wear is at the bottom of the guide (seat end), then you know you have a seat to guide concentricity issue.
If wear is in an hour glass shape, which end has more wear? Again, that will tell you where the problem originated from. If it is equal at the top and bottom, then the guide clearance was too much after initial machine work was done.
So really, without thoroughly mapping the wear with precision instruments, you should not make assumptions and just change worn components, because you may not be addressing the problem that caused the wear.
If you have wear from rocker loading, it doesn’t matter what type of guild you go with, or cylinder head manufacture. The same problem will happen again, unless you do something to fix the rocker loading issue.
For example, if the guides with excessive clearance are within spec at the bottom (valve seat end), but are showing excessive clearance at the top (rocker end), then you know that the valve has been side loaded by the rocker. Now look again at your map. Is the wear uniform? – this will be very unlikely. Is the wear in the direction from the front of the engine to the back? Or, is it in the direction across the head from intake to exhaust? Knowing this will tell you how the rocker was loading the valve stem. Normally, you’ll see it in the intake to exhaust direction, and that will tell you that you either have too much lift for the OE rocker, or there was too much friction from impropper tip or rocker pad finish, or a combination of both. You can at this point decide if you would rather run less lift, or move to a roller tipped rocker.
If the wear is at the bottom of the guide (seat end), then you know you have a seat to guide concentricity issue.
If wear is in an hour glass shape, which end has more wear? Again, that will tell you where the problem originated from. If it is equal at the top and bottom, then the guide clearance was too much after initial machine work was done.
So really, without thoroughly mapping the wear with precision instruments, you should not make assumptions and just change worn components, because you may not be addressing the problem that caused the wear.
If you have wear from rocker loading, it doesn’t matter what type of guild you go with, or cylinder head manufacture. The same problem will happen again, unless you do something to fix the rocker loading issue.
Last edited by RamAir972003; 04-16-2015 at 11:55 AM.
04-15-2015, 09:13 PM
#50
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ppl might want to think about getting rid of the ls7 casting an going with an ls3 heads and intake rockes ect. may loose some power but its worth a try, getting ready to test this soon. And what you posted about Darin is the reason I wont touch another ls7 head. for anyone
Last edited by chadyellowz; 04-15-2015 at 09:26 PM.
04-15-2015, 10:51 PM
#51
there isn't a fix that i can see with the stock casting. i've seen the same thing you talk about with Darin, thats why I knew it was never valve seat run out or valve seat concentricity issue. to many ppl have checked this and still wearing guides ppl might want to think about getting rid of the ls7 casting an going with an ls3 heads and intake rockes ect. may loose some power but its worth a try, getting ready to test this soon. And what you posted about Darin is the reason I wont touch another ls7 head. for anyone
ppl might want to think about getting rid of the ls7 casting an going with an ls3 heads and intake rockes ect. may loose some power but its worth a try, getting ready to test this soon. And what you posted about Darin is the reason I wont touch another ls7 head. for anyone
04-15-2015, 11:54 PM
#52
That's what I'm thinking of maybe doing next, Mast is what I'm thinking. I am just tapped out with spending time and money on assumption's, you know I have always tried to help everyone here but when there's no cure there's only trial and error I guess. It would be nice I would do it I can get some money and just totally do a custom head for the ls7 Maybe copy ls3 but keep the chambers and flow about the same. I just don't know. If we could all get together and I would def get Darin or ask him to design a set. Prob looking at around 5 or 6k or so...which is no problem if people really want to go through with it I'm all in. Now by far the ls7 is and probably the best ever made small block with that kind of power to go in an American vehicle I just think well if its beating 8.0 liter motors and making up to 200hp more with heads cam e85 or race gas I personally think that motor is just a work of art, some quality control issues and head issues but look at the Ls3 bolt on supercharger and your making serious power. I just can't figure this out.
Last edited by RamAir972003; 04-16-2015 at 12:04 AM.
04-16-2015, 09:33 AM
#53
Yes. Just keep in mind that that valve side of the rocker pivot; mass-MOI will be increased. So, if used, additional spring rate will be required to maintain current peak RPM. And, with added spring pressure, you will increase friction and wear to the valve train. There is no free lunch.
At this point in the conversation with you, I have no frigging idea what you have done. You might consider taking a writing class. Is English your first language? Maybe that's why I can't follow you.
There is a solution - careful analysis of the failure by a competent person. I have not seen a single measurement from you yet. All I hear is, "heads bad" from you. Show me your guide wear map. What is your total lift? Did you check rocker scrub? What are your spring pressures? What is your spring install height? Did you verify seat run-out? What was it?
I'd just love to hear your theories that support you hypothesis that GM LS7 cylinder head castings can't be fixed. And to go with an LS3 head on a 4.125 bore? That's not a good idea.
Excessive seat concentricity is, in fact, something that has been measured and confirmed on new GM castings. Is it the only problem with stock set ups? Probably not. But to say it is not an issue, is simply incorrect.
I do have one theory, that could very well lead to exhaust valve failure. Has to do with coolant. I won't spoil the ending till I hear your theories.
There is a solution - careful analysis of the failure by a competent person. I have not seen a single measurement from you yet. All I hear is, "heads bad" from you. Show me your guide wear map. What is your total lift? Did you check rocker scrub? What are your spring pressures? What is your spring install height? Did you verify seat run-out? What was it?
there isn't a fix that i can see with the stock casting. i've seen the same thing you talk about with Darin, thats why I knew it was never valve seat run out or valve seat concentricity issue. to many ppl have checked this and still wearing guides ppl might want to think about getting rid of the ls7 casting an going with an ls3 heads and intake rockes ect. may loose some power but its worth a try, getting ready to test this soon. And what you posted about Darin is the reason I wont touch another ls7 head. for anyone
ppl might want to think about getting rid of the ls7 casting an going with an ls3 heads and intake rockes ect. may loose some power but its worth a try, getting ready to test this soon. And what you posted about Darin is the reason I wont touch another ls7 head. for anyoneExcessive seat concentricity is, in fact, something that has been measured and confirmed on new GM castings. Is it the only problem with stock set ups? Probably not. But to say it is not an issue, is simply incorrect.
I do have one theory, that could very well lead to exhaust valve failure. Has to do with coolant. I won't spoil the ending till I hear your theories.
04-16-2015, 11:38 AM
#55
T
I dont know what your problem is with your post about my English has nothing to do with what I wrote. I have spoken to you before on the phone I sent this from my phone so if you can't interpretate what I wrote then I guess dont respond please. Measurements for what they were seen by the naked eye just a waste of time to get measurements. If you think you have figured out a solution about this issue please elaborate instead of sitting here and trying to tell me about measurements. What is you said put up or shut up. No offense Michael I will fly you out here so you can show me and Darin your theory's on this excessive failure. My opinion is still that there is no fix, you can machine everything correctly and use expensive parts.So what happens when you pull the heads at 20k and there is guide wear again. Rockers and spring pressures were matched with cam or cams always. Pm if you need to me to better explain to you, I have no problem talking over a lan line. With all due respect. Michael I can get another set of heads if you like I will ship them to you and you can do your magic, I will pay for your time if you like hopefully that will be fair and understanding. Money is the universal language.
Yes. Just keep in mind that that valve side of the rocker pivot; mass-MOI will be increased. So, if used, additional spring rate will be required to maintain current peak RPM. And, with added spring pressure, you will increase friction and wear to the valve train. There is no free lunch.
At this point in the conversation with you, I have no frigging idea what you have done. You might consider taking a writing class. Is English your first language? Maybe that's why I can't follow you.
There is a solution - careful analysis of the failure by a competent person. I have not seen a single measurement from you yet. All I hear is, "heads bad" from you. Show me your guide wear map. What is your total lift? Did you check rocker scrub? What are your spring pressures? What is your spring install height? Did you verify seat run-out? What was it?
The measurements on my first set were posted in my past threads by Darin Morgan. The second set is what I'm currently running now. Its the get-20 cam on a 112 lsa ...I bealive its 20 degrees of over lap. Rockers are stock with grunion upgrade. Springs are PAC 650 lift max. 5w30 mobile one. 64k was install currently 81222 miles. Now pictured of my guide wear can be seen on my build in my previous posts.
I'd just love to hear your theories that support you hypothesis that GM LS7 cylinder head castings can't be fixed. And to go with an LS3 head on a 4.125 bore? That's not a good idea.
Excessive seat concentricity is, in fact, something that has been measured and confirmed on new GM castings. Is it the only problem with stock set ups? Probably not. But to say it is not an issue, is simply incorrect.
I do have one theory, that could very well lead to exhaust valve failure. Has to do with coolant. I won't spoil the ending till I hear your theories.
At this point in the conversation with you, I have no frigging idea what you have done. You might consider taking a writing class. Is English your first language? Maybe that's why I can't follow you.
There is a solution - careful analysis of the failure by a competent person. I have not seen a single measurement from you yet. All I hear is, "heads bad" from you. Show me your guide wear map. What is your total lift? Did you check rocker scrub? What are your spring pressures? What is your spring install height? Did you verify seat run-out? What was it?
The measurements on my first set were posted in my past threads by Darin Morgan. The second set is what I'm currently running now. Its the get-20 cam on a 112 lsa ...I bealive its 20 degrees of over lap. Rockers are stock with grunion upgrade. Springs are PAC 650 lift max. 5w30 mobile one. 64k was install currently 81222 miles. Now pictured of my guide wear can be seen on my build in my previous posts.
I'd just love to hear your theories that support you hypothesis that GM LS7 cylinder head castings can't be fixed. And to go with an LS3 head on a 4.125 bore? That's not a good idea.
Excessive seat concentricity is, in fact, something that has been measured and confirmed on new GM castings. Is it the only problem with stock set ups? Probably not. But to say it is not an issue, is simply incorrect.
I do have one theory, that could very well lead to exhaust valve failure. Has to do with coolant. I won't spoil the ending till I hear your theories.
I dont know what your problem is with your post about my English has nothing to do with what I wrote. I have spoken to you before on the phone I sent this from my phone so if you can't interpretate what I wrote then I guess dont respond please. Measurements for what they were seen by the naked eye just a waste of time to get measurements. If you think you have figured out a solution about this issue please elaborate instead of sitting here and trying to tell me about measurements. What is you said put up or shut up. No offense Michael I will fly you out here so you can show me and Darin your theory's on this excessive failure. My opinion is still that there is no fix, you can machine everything correctly and use expensive parts.So what happens when you pull the heads at 20k and there is guide wear again. Rockers and spring pressures were matched with cam or cams always. Pm if you need to me to better explain to you, I have no problem talking over a lan line. With all due respect. Michael I can get another set of heads if you like I will ship them to you and you can do your magic, I will pay for your time if you like hopefully that will be fair and understanding. Money is the universal language.
Last edited by RamAir972003; 04-16-2015 at 12:25 PM.
04-16-2015, 12:10 PM
#56
Team Owner
there isn't a fix that i can see with the stock casting. i've seen the same thing you talk about with Darin, thats why I knew it was never valve seat run out or valve seat concentricity issue. to many ppl have checked this and still wearing guides ppl might want to think about getting rid of the ls7 casting an going with an ls3 heads and intake rockes ect. may loose some power but its worth a try, getting ready to test this soon. And what you posted about Darin is the reason I wont touch another ls7 head. for anyone
ppl might want to think about getting rid of the ls7 casting an going with an ls3 heads and intake rockes ect. may loose some power but its worth a try, getting ready to test this soon. And what you posted about Darin is the reason I wont touch another ls7 head. for anyoneIs that flaw also in the aftermarket heads, such as the PRC265 heads?
Can the LS3 head be made to flow as well as the LS7 head at the same valve lift using the stock cam without having to go with a more aggressive cam profile?
If one goes with a LS3 head, don't you have to go with a LS3 intake manifold? Will it flow as well as the LS7 intake manifold?
04-16-2015, 12:20 PM
#57
T
I dont know what your problem is with your post about my English has nothing to do with what I wrote. I have spoken to you before on the phone I sent this from my phone so if you can't interpretate what I wrote then I guess dont respond please. Measurements for what they were seen by the naked eye just a waste of time to get measurements. If you think you have figured out a solution about this issue please elaborate instead of sitting here and trying to tell me about measurements. What is you said put up or shut up. No offense Michael I will fly you out here so you can show me and Darin your theory's on this excessive failure. My opinion is still that there is no fix, you can machine everything correctly and use expensive parts so what happens when you pull the heads at 20k and there is guide wear again. Rockers and spring pressures were matched with cam or cams always. Pm if you need to me to better explain to you, I have no problem talking over a lan line.
I dont know what your problem is with your post about my English has nothing to do with what I wrote. I have spoken to you before on the phone I sent this from my phone so if you can't interpretate what I wrote then I guess dont respond please. Measurements for what they were seen by the naked eye just a waste of time to get measurements. If you think you have figured out a solution about this issue please elaborate instead of sitting here and trying to tell me about measurements. What is you said put up or shut up. No offense Michael I will fly you out here so you can show me and Darin your theory's on this excessive failure. My opinion is still that there is no fix, you can machine everything correctly and use expensive parts so what happens when you pull the heads at 20k and there is guide wear again. Rockers and spring pressures were matched with cam or cams always. Pm if you need to me to better explain to you, I have no problem talking over a lan line.
If you don’t take measurements, and you just “look” at the valve moving around, then you do not know what the cause of the wear was/is. If you would have read, and understood my earlier post, you would realize that by not taking measurements, you are just guessing. So….you obviously do not understand a topic that you are being quite vocal about.
“Put up or shut up”? What the *** are you saying??? You better calm down there buckwheat. I’m not some zit faced 13 YO girl hiding behind a keyboard on mommy’s basement.
So one more time, you gunna provide answers to my earlier questions? Telling me “rockers and spring pressures were matched with cam or cams always” is a bullshiit statement. You didn't tell me anything, other than you just don’t know.
So one more time: What’s the total lift? Are you running OEM rockers? What is your spring rates? Is the guide wear more towards the top of the guide, or the bottom?
04-16-2015, 12:40 PM
#58
My “problem” as you put it, is you are not clear with what you’ve done, or what you are doing. I asked about English, as your writing indicates that you have problems with following a line of conversation. And yes, I remember the phone conversation. I called you, per your request. I was also quite clear, but you apparently did not comprehend.
If you don’t take measurements, and you just “look” at the valve moving around, then you do not know what the cause of the wear was/is. If you would have read, and understood my earlier post, you would realize that by not taking measurements, you are just guessing. So….you obviously do not understand a topic that you are being quite vocal about.
“Put up or shut up”? What the *** are you saying??? You better calm down there buckwheat. I’m not some zit faced 13 YO girl hiding behind a keyboard on mommy’s basement.
So one more time, you gunna provide answers to my earlier questions? Telling me “rockers and spring pressures were matched with cam or cams always” is a bullshiit statement. You didn't tell me anything, other than you just don’t know.
So one more time: What’s the total lift? Are you running OEM rockers? What is your spring rates? Is the guide wear more towards the top of the guide, or the bottom?
If you don’t take measurements, and you just “look” at the valve moving around, then you do not know what the cause of the wear was/is. If you would have read, and understood my earlier post, you would realize that by not taking measurements, you are just guessing. So….you obviously do not understand a topic that you are being quite vocal about.
“Put up or shut up”? What the *** are you saying??? You better calm down there buckwheat. I’m not some zit faced 13 YO girl hiding behind a keyboard on mommy’s basement.
So one more time, you gunna provide answers to my earlier questions? Telling me “rockers and spring pressures were matched with cam or cams always” is a bullshiit statement. You didn't tell me anything, other than you just don’t know.
So one more time: What’s the total lift? Are you running OEM rockers? What is your spring rates? Is the guide wear more towards the top of the guide, or the bottom?
Last edited by RamAir972003; 04-16-2015 at 01:03 PM.
04-16-2015, 12:59 PM
#59
Team Owner
The reason in being vocal is because I explained to you remember I told you I was going to go with gt-20 cam on a 112 lsa with about a 20 degree overlap, rockers are stock you said I should be fine, also did trunion upgrade. So springs are PAC 650 max lift springs. You told me I should be fine if previous rockers showed no signs of uneven surfaces on head. Verified and assembled by Darin Morgan. Heads are milled for stock compression maybe 0.15 to make them flat and even. Sorry if I upset you Michael I just wanted to get your attention no offense I hope. So question to you is am I fine or should I pull the heads and check for guide wear again. I measured everything before I sent heads in , ok ill go over this again in case you forgot. Heads were orginally sold to me assembled and new I disassembled and remeasured everything before I installed milled the heads and I am currently at 81k miles. Car is always running at 178f Texas heat it has gone up to 210f... I mean what more can I possibly have missed. In your opinion should I pull them now or wait. Currently at have not checked the guide wear, and no MIchael_D I dont have my spring rates sorry, but I'm sure I can get them for you. Please pm. Or i can call you thanks sorry if I upset you brother.
04-16-2015, 01:15 PM
#60