[Z06] KATECH PSA: LS7/LS9 cylinder heads, valve guides, valves and rocker arms
03-21-2012, 10:41 AM
#41
Melting Slicks
I'll be surprised if anyone, including Jason will ever be able to say with 100% certainty why some guides in LS7's and LS9's show more wear than other engines. Personally I think that nearly .600 lift, with a 5/16 valve stem, along with the possibility that some owners run these things at 1400-1600rpm in 6th gear, for extended periods under heavy load, could have something to do with it. Think about it..........low rpm, low volume of oil splashing on the valve stems, lean intake mixture, heavy load, and elevated coolant temp. Under those conditions that one and a half to two thousands clearance between the stem and the guide can disappear in a hurry. When that happens, any remaining oil gets cooked, the valve galls the guide, material transfers onto the stem, and the clearance opens up. Can't prove it.......just saying, seems plausible to me.
03-21-2012, 10:59 AM
#42
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AzDave.....In response to your question.... indeed, think big long hills. In fact, they don't even need to be that big. Just long, and in 6th gear around 70-75mph.
Just saying that heavy loading of the engine up a grade in 6th will raise combustion temps rapidly, and potentially overheat the valves.
Just saying that heavy loading of the engine up a grade in 6th will raise combustion temps rapidly, and potentially overheat the valves.
03-21-2012, 11:06 AM
#43
..... If this concerns you, replace the stock guides with bronze. When doing so, you need to change the intake valves to Katech titanium/molybdenum valves because the molybdenum coating has better material compatibility with the bronze. These valves also have steel tip that eliminates the lash caps. ..... What you read above in this paragraph is what we know and what you need to know. We don't know what the root cause of the wear is, but the fix is noted above.
That is all.
That is all.
03-21-2012, 11:12 AM
#44
Race Director
Since it takes about 20HP to cruise on the level at 65 mph, my guess is going up a big long hill would possibly take 100HP, maybe even 200hp, but in no way should that be a stress on our LS7 engines. I bet my HP estimates are high, given the fuel mileage we get on the highway. Since I drive from Phoenix up into the mountains and have done other similar long grades while still getting great mileage, it can't be taking that much HP.
BTW, I got 18.8 MPH doing the Silver State Challenge, 90 miles at 110MPH average with almost exclusively 6th gear cruise last September, which would also confirm the lower HP estimate.
BTW, I got 18.8 MPH doing the Silver State Challenge, 90 miles at 110MPH average with almost exclusively 6th gear cruise last September, which would also confirm the lower HP estimate.
03-21-2012, 11:19 AM
#45
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03-21-2012, 11:20 AM
#46
Race Director
AzDave.....In response to your question.... indeed, think big long hills. In fact, they don't even need to be that big. Just long, and in 6th gear around 70-75mph.
Just saying that heavy loading of the engine up a grade in 6th will raise combustion temps rapidly, and potentially overheat the valves.
Just saying that heavy loading of the engine up a grade in 6th will raise combustion temps rapidly, and potentially overheat the valves.
I'll check the oil temp the next time I go up a big, long hill. Since it normally runs about 150*, maybe it will go up to 180* (which would be a better range anyway).
03-21-2012, 11:49 AM
#47
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If I'm tooting along at 70mph in 6th on level ground, it may in fact only take 20HP to maintain that speed, I dunno. For this discussion, what matters is loading and RPM. If a hill happens to get in the way and the car starts to slow down I have two choices to maintain my speed, either squeeze the throttle which will increase the load on the engine and raise combustion chamber temp, or downshift to a lower gear which will reduce reduce loading and combustion temp. Simple deal.
As far as oil and coolant temp are concerned what happens to them is to a great extent the result of what's going on with combustion temps.
As far as oil and coolant temp are concerned what happens to them is to a great extent the result of what's going on with combustion temps.
03-21-2012, 12:06 PM
#49
Thanks for posting this Jason. I commend you for stepping up and call BS.
I believe most head shops who recommend a solid exh valve do so because it is difficult to find a hollow stem valve. There are a couple options out there, but they are expensive, with a rather long lead time and they are not a simple drop in 8mm stem replacement. I just went through this and my porter was not able to get me an alternative hollow stem valve for several weeks as the blanks were coming out of Argentina. There is an Israeli supplier that has a hollow stem valve that will work nicely, but they are $80 a piece and at that price, Ti becomes a more attractive option. But with Ti, Mold Star seats are required and you loose some heat transfer efficiencies. I decided to just stick with OE valves and DMBK guide liners.
And then of course there is the misconceived paranoia around hollow stem or two piece valve use that the ignorant expound on. If a head shop were to recommend staying OE, they know the misinformed potential customer would have a come-apart and take their business elsewhere - just a theory. A lot of this paranoia I suspect is a carryover from 351 C Ford FE motors in the 70's that were dropping valves left and right.
Oh, and we might as well put the whole "dual springs are better than one" wives's tale to rest too. I can't help but laugh when I hear this. A good beehive will outperform a dual spring any day of the week (provided it has the correct rate of course). "But if one spring fails, the second will keep the valve from dropping"...lol... If one spring is unhappily rubbing against another spring, do you really think the other spring will be happy? lol...
I believe most head shops who recommend a solid exh valve do so because it is difficult to find a hollow stem valve. There are a couple options out there, but they are expensive, with a rather long lead time and they are not a simple drop in 8mm stem replacement. I just went through this and my porter was not able to get me an alternative hollow stem valve for several weeks as the blanks were coming out of Argentina. There is an Israeli supplier that has a hollow stem valve that will work nicely, but they are $80 a piece and at that price, Ti becomes a more attractive option. But with Ti, Mold Star seats are required and you loose some heat transfer efficiencies. I decided to just stick with OE valves and DMBK guide liners.
And then of course there is the misconceived paranoia around hollow stem or two piece valve use that the ignorant expound on. If a head shop were to recommend staying OE, they know the misinformed potential customer would have a come-apart and take their business elsewhere - just a theory. A lot of this paranoia I suspect is a carryover from 351 C Ford FE motors in the 70's that were dropping valves left and right.
Oh, and we might as well put the whole "dual springs are better than one" wives's tale to rest too. I can't help but laugh when I hear this. A good beehive will outperform a dual spring any day of the week (provided it has the correct rate of course). "But if one spring fails, the second will keep the valve from dropping"...lol... If one spring is unhappily rubbing against another spring, do you really think the other spring will be happy? lol...
03-21-2012, 12:06 PM
#50
Race Director
C6 Mayhem & musicmankeb: I've not run into a hill so steep that I can't maintain 1600RPM in 6th, mostly even at part throttle, which is less than 150HP. Since our engines get used under far more stressful conditions (twisties uphill in 2nd & 3rd gear, full throttle runs, HPDE's, 1/4 mile's), I just can't see uphill in 6th gear at 1600 RPM being so stressful as to create valve problems discussed in this thread - no way.
Actually this is about Katech's update on their experience and findings, which I appreciate.
Actually this is about Katech's update on their experience and findings, which I appreciate.
Last edited by AzDave47; 03-21-2012 at 12:09 PM.
03-21-2012, 12:08 PM
#51
I've been told by an industry expert that Dell West Nitride coated titanium valves originally were very rough and were causing accelerated valve guide wear with all valve guide materials. About 18 months ago they improved the coating and now there is no issue.
If the 'rough' version of these valves have been in a head for some time the original guides have sacrificed themselves to the job of 'smoothing out' this original roughness. There should be no issue in reusing these valves with new guides. Just for insurance, it doesn't hurt to check them for residual roughness.
This helps explain the source of the odd intake valve guide wear many LS7s have experienced.
I did not know about this until I spoke with the expert today. He said this was well known in the industry.
The fact that Katech is recommending titanium/molybdenum for new engines doesn't hurt; however, this advice does not take into account the improvement that Dell West has recently made to their Nitride coating process; nor, does it apply to the use of 'smoothed-in-use' older OEM intake valves.
Jason, why don't you verify this and clarify Katech's recommendations.
If the 'rough' version of these valves have been in a head for some time the original guides have sacrificed themselves to the job of 'smoothing out' this original roughness. There should be no issue in reusing these valves with new guides. Just for insurance, it doesn't hurt to check them for residual roughness.
This helps explain the source of the odd intake valve guide wear many LS7s have experienced.
I did not know about this until I spoke with the expert today. He said this was well known in the industry.
The fact that Katech is recommending titanium/molybdenum for new engines doesn't hurt; however, this advice does not take into account the improvement that Dell West has recently made to their Nitride coating process; nor, does it apply to the use of 'smoothed-in-use' older OEM intake valves.
Jason, why don't you verify this and clarify Katech's recommendations.
03-21-2012, 12:11 PM
#52
Burning Brakes
You're oil temps are very low, how do you burn out the condensation in your oil?
Since dyno runs aren't done down at 1600 RPM, I don't have a solid number, but projecting back on the runs on my stock 09 Z06, it is making between 80-100HP at 1600 RPM. It made 150HP at 2200 RPM. The oil temp may go up some but the water temp stays below 200* at 75MPH.
I'll check the oil temp the next time I go up a big, long hill. Since it normally runs about 150*, maybe it will go up to 180* (which would be a better range anyway).
I'll check the oil temp the next time I go up a big, long hill. Since it normally runs about 150*, maybe it will go up to 180* (which would be a better range anyway).
03-21-2012, 12:14 PM
#53
Le Mans Master
Know if its the valves or the valve guides makes no difference. Both are going to be damaged when you open it up. Secondly it seems to be a heat issue from every which way you look at it. Now if I am going to point fingers at something I am going to choose the oil pump. Here is my reasoning. Most failures happen at the extremes of low low low rpm or high high high rpm. Both points are where either an oil pump isn't pumping enough due to the low rpms or its pumping at full max but isn't efficient enough to keep up with the demands. Sorry but it makes absolutely no sense to add the larger tank as a solution. The only benefit from that is larger volume of fluid to carry more heat and give it longer to heat/cool. Also the larger tank isn't something to stop cavitation of the pump. The tank is an auxiliary zone added to the side. Not following me? Fill a glass half way up with water and tip it. The outlet for your oil to your pumps is at that bottom of your tank. Now whats interesting is the ZR1 has an upgraded oil pump and I am yet to see a documented case of a dropped valve or blown motor yet. I would be more concerned that the cause is oil pump related also due to the argument of bearings getting toasted due to oil not being pumped. It has been reported that the issue is only seen when making hard left handers. Hmmmmm seems the pump cannot oppose the G-forces applied against the oil it is pushing. If it was a tank issue then you would see it when making hard right handers too. Also if I am correct the LS9 runs the same valves and guides. What I would be interested to see is if the 09-12 Z06 runs the same pump as the ZR1.
And another thing to say oh latent damage to a HOLLOW 2 PIECE valve is the cause is just stupid. YOU DON'T JUST BEND ONE VALVE WHEN YOU MIS-SHIFT. Also I am pretty sure we have all driven tons of cars before. We have raced cars before. Why all of the sudden are we bending valves.
Jason I think you are on point with what you are saying. The root cause isn't really definable, and most of the thoughts are just theories.
A suggestion to people that keep on wondering what to do. I would just cover all my bases by replacing all the worrisome parts or sell the car and get something else.
And another thing to say oh latent damage to a HOLLOW 2 PIECE valve is the cause is just stupid. YOU DON'T JUST BEND ONE VALVE WHEN YOU MIS-SHIFT. Also I am pretty sure we have all driven tons of cars before. We have raced cars before. Why all of the sudden are we bending valves.
Jason I think you are on point with what you are saying. The root cause isn't really definable, and most of the thoughts are just theories.
A suggestion to people that keep on wondering what to do. I would just cover all my bases by replacing all the worrisome parts or sell the car and get something else.
Last edited by whatcop?; 03-21-2012 at 12:35 PM.
03-21-2012, 12:28 PM
#54
Race Director
I'm running M1 5w-30EP right now and back off at HPDE events when the oil gets to 260*. My next fill will probably be M1 0w-40 and I will likely run it higher. The oil temp gauge doesn't seem concerned until the oil gets to 300* which I've never seen and wouldn't want to run any street oils to that temp.
03-21-2012, 12:41 PM
#56
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Drew..If your question is directed at me...45 years combined experience as a machinist/engine builder, technician and dealership service manager, with a few years thrown in working for an engineering company producing components for Cup and IRL. As far as how many LS7's I've wrenched on...only one, mine. I'm retired.
Point of fact, the LS7 is not the eighth wonder of the world. It's just a big pushrod V8 with a very high lift cam (for a street application), good compression, and a great set of heads. All the old rules learned in the 60's still apply. A lot of heads crossed my bench when I was a machinist. I saw lots of loose guides and pounded valve seats. Based on what I know, I'm just expressing an opinion....If you run it long enough, up a grade under sustained load at low RPM there's a risk of overheating the valves, exhaust first.
Point of fact, the LS7 is not the eighth wonder of the world. It's just a big pushrod V8 with a very high lift cam (for a street application), good compression, and a great set of heads. All the old rules learned in the 60's still apply. A lot of heads crossed my bench when I was a machinist. I saw lots of loose guides and pounded valve seats. Based on what I know, I'm just expressing an opinion....If you run it long enough, up a grade under sustained load at low RPM there's a risk of overheating the valves, exhaust first.
03-21-2012, 12:47 PM
#57
Le Mans Master
Drew..If your question is directed at me...45 years combined experience as a machinist/engine builder, technician and dealership service manager, with a few years thrown in working for an engineering company producing components for Cup and IRL. As far as how many LS7's I've wrenched on...only one, mine. I'm retired.
Point of fact, the LS7 is not the eighth wonder of the world. It's just a big pushrod V8 with a very high lift cam (for a street application), good compression, and a great set of heads. All the old rules learned in the 60's still apply. A lot of heads crossed my bench when I was a machinist. I saw lots of loose guides and pounded valve seats. Based on what I know, I'm just expressing an opinion....If you run it long enough, up a grade under sustained load at low RPM there's a risk of overheating the valves, exhaust first.
Point of fact, the LS7 is not the eighth wonder of the world. It's just a big pushrod V8 with a very high lift cam (for a street application), good compression, and a great set of heads. All the old rules learned in the 60's still apply. A lot of heads crossed my bench when I was a machinist. I saw lots of loose guides and pounded valve seats. Based on what I know, I'm just expressing an opinion....If you run it long enough, up a grade under sustained load at low RPM there's a risk of overheating the valves, exhaust first.
: lol
03-21-2012, 01:28 PM
#60
Le Mans Master
I've been told by an industry expert that Dell West Nitride coated titanium valves originally were very rough and were causing accelerated valve guide wear with all valve guide materials. About 18 months ago they improved the coating and now there is no issue.
If the 'rough' version of these valves have been in a head for some time the original guides have sacrificed themselves to the job of 'smoothing out' this original roughness. There should be no issue in reusing these valves with new guides. Just for insurance, it doesn't hurt to check them for residual roughness.
This helps explain the source of the odd intake valve guide wear many LS7s have experienced.
I did not know about this until I spoke with the expert today. He said this was well known in the industry.
The fact that Katech is recommending titanium/molybdenum for new engines doesn't hurt; however, this advice does not take into account the improvement that Dell West has recently made to their Nitride coating process; nor, does it apply to the use of 'smoothed-in-use' older OEM intake valves.
Jason, why don't you verify this and clarify Katech's recommendations.
If the 'rough' version of these valves have been in a head for some time the original guides have sacrificed themselves to the job of 'smoothing out' this original roughness. There should be no issue in reusing these valves with new guides. Just for insurance, it doesn't hurt to check them for residual roughness.
This helps explain the source of the odd intake valve guide wear many LS7s have experienced.
I did not know about this until I spoke with the expert today. He said this was well known in the industry.
The fact that Katech is recommending titanium/molybdenum for new engines doesn't hurt; however, this advice does not take into account the improvement that Dell West has recently made to their Nitride coating process; nor, does it apply to the use of 'smoothed-in-use' older OEM intake valves.
Jason, why don't you verify this and clarify Katech's recommendations.
