[Z06] Qustions for Darrin Morgan.......
07-02-2015, 10:27 AM
#121
Team Owner
Darin, care to weigh in on valve control/spintron/etc. Lots of people here think you can't control a SS valve, that dual springs are bad.
07-02-2015, 10:39 AM
#122
Le Mans Master
07-02-2015, 03:37 PM
#123
Safety Car
I'm the type that enjoys seeing things, more than reading about it. Hope you change your mind or find a way to share with those with interest.
07-02-2015, 06:19 PM
#124
Safety Car
I appreciate your change of heart.I'm not here to take sides or stir pots or stroke anyones ego. I'm just interested in learning what's going on with this.
I hope we can all forget the sandbox fighting and stay on subject. Thanks.
07-02-2015, 06:35 PM
#125
Le Mans Master
These are awesome Vettes and the more we can learn and get corrected, the better imo.
07-03-2015, 12:27 PM
#126
I don’t like hollow exhaust valves in any engine.
In my opinion, they should never be used in a high performance engine. Not that they won’t function perfectly in this rare instance but in all other instances the results have been less than favorable. I can only think of one instance in high performance engines where hollow exhaust valves are used and that’s only because there rule book outlawed Titanium valves otherwise they would be running Titanium. There are instances in racing where engine builders MUST use hollow stem exhaust valves due to the fact that there rule book outlaws Titanium or other nonferrous metals (NHRA Super Stock for instance). Given a choice in the matter, I will run either a solid stem exhaust valve designed for reduced weight or use Titanium once the valve train control becomes a problem.
(1) My solid stem high nickel stainless exhaust valves for the LS7 weigh in at 94.5grams. Surely anyone can control a 95gram exhaust valve to 7000rpm using the springs we have at our disposable today. People forget that the exhaust gas is helping the exhaust valve close so having it slightly heavier than the intake is not a factor.
(2) If you operate your engine to 7500rpm or higher, you need Titanium valves. I said you need them I didn't say you cant get way with turning an engine 7500rpm with steal valves. Just wanted to head this question off at the pass. LOL You can get way with it but Ti valves will make a LOT more power and cost less in the long run because they control the valve train better.
As far as changing seat material goes, yes you should. Can you get away with not doing it? Sure you can. The stock seat material seems to work rather well with Ti valves. That’s not to say you won’t get more valve life out of copper seats, you will. I have been pleasantly surprised at the lack of seat wear in the LS7 road race heads that utilize Ti exhaust valves. We don’t use any coatings on the exhaust valves because to date, all coating on the exhaust valves in race engines have failed. Some quickly some slowly over time.
I did not mean oil doesn’t matter simply by omitting it from my answer. It’s not really specific to this discussion. I left a lot of stuff out of my answer because I wanted to narrow things down to the root causes and not get off on tangents as these threads so often do. Will oil with the proper amount of ZDDP help with valve guide problems, yes. The proper oil helps with everything! Ring seal, ring life, valve guide life, Rocker arm tip life, bearing life, reduced component operating temperature, I could go on and on.
In my opinion, they should never be used in a high performance engine. Not that they won’t function perfectly in this rare instance but in all other instances the results have been less than favorable. I can only think of one instance in high performance engines where hollow exhaust valves are used and that’s only because there rule book outlawed Titanium valves otherwise they would be running Titanium. There are instances in racing where engine builders MUST use hollow stem exhaust valves due to the fact that there rule book outlaws Titanium or other nonferrous metals (NHRA Super Stock for instance). Given a choice in the matter, I will run either a solid stem exhaust valve designed for reduced weight or use Titanium once the valve train control becomes a problem. (1) My solid stem high nickel stainless exhaust valves for the LS7 weigh in at 94.5grams. Surely anyone can control a 95gram exhaust valve to 7000rpm using the springs we have at our disposable today. People forget that the exhaust gas is helping the exhaust valve close so having it slightly heavier than the intake is not a factor.
(2) If you operate your engine to 7500rpm or higher, you need Titanium valves. I said you need them I didn't say you cant get way with turning an engine 7500rpm with steal valves. Just wanted to head this question off at the pass. LOL You can get way with it but Ti valves will make a LOT more power and cost less in the long run because they control the valve train better.
As far as changing seat material goes, yes you should. Can you get away with not doing it? Sure you can. The stock seat material seems to work rather well with Ti valves. That’s not to say you won’t get more valve life out of copper seats, you will. I have been pleasantly surprised at the lack of seat wear in the LS7 road race heads that utilize Ti exhaust valves. We don’t use any coatings on the exhaust valves because to date, all coating on the exhaust valves in race engines have failed. Some quickly some slowly over time.
I did not mean oil doesn’t matter simply by omitting it from my answer. It’s not really specific to this discussion. I left a lot of stuff out of my answer because I wanted to narrow things down to the root causes and not get off on tangents as these threads so often do. Will oil with the proper amount of ZDDP help with valve guide problems, yes. The proper oil helps with everything! Ring seal, ring life, valve guide life, Rocker arm tip life, bearing life, reduced component operating temperature, I could go on and on.
I really don't want to belabor the same question, but can you provide some more detail on what it is you find, or have seen with respect to hollow stemmed exh valve problems? What exactly does "less than favorable" mean? Other than the most obvious, PTVC, I'd like to know what else can, or does happen.
With the exception of some older Ford engines, this LS7 is the first engine I've screwed with that uses these valves on the exh.
Controlling this valve train to 7000 isn't the concern, it's the over revs. There are some, myself included, who want a good 600-800rpm over fuel cutoff speed for these situations (I have personally seen 7600rpm twice now). Until someone shows me verified sprin rig results of a 95g valve staying in control at 7600rpm, I will not consider using one.
The next time I yank these damn heads off, I'm stuffing Ti valves in both sides, like I had intended to do several years ago, but was talked out of doing so....
07-03-2015, 01:09 PM
#128
Le Mans Master
Thanks for that respond Darin.
I really don't want to belabor the same question, but can you provide some more detail on what it is you find, or have seen with respect to hollow stemmed exh valve problems? What exactly does "less than favorable" mean? Other than the most obvious, PTVC, I'd like to know what else can, or does happen.
With the exception of some older Ford engines, this LS7 is the first engine I've screwed with that uses these valves on the exh.
Controlling this valve train to 7000 isn't the concern, it's the over revs. There are some, myself included, who want a good 600-800rpm over fuel cutoff speed for these situations (I have personally seen 7600rpm twice now). Until someone shows me verified sprin rig results of a 95g valve staying in control at 7600rpm, I will not consider using one.
The next time I yank these damn heads off, I'm stuffing Ti valves in both sides, like I had intended to do several years ago, but was talked out of doing so....
I really don't want to belabor the same question, but can you provide some more detail on what it is you find, or have seen with respect to hollow stemmed exh valve problems? What exactly does "less than favorable" mean? Other than the most obvious, PTVC, I'd like to know what else can, or does happen.
With the exception of some older Ford engines, this LS7 is the first engine I've screwed with that uses these valves on the exh.
Controlling this valve train to 7000 isn't the concern, it's the over revs. There are some, myself included, who want a good 600-800rpm over fuel cutoff speed for these situations (I have personally seen 7600rpm twice now). Until someone shows me verified sprin rig results of a 95g valve staying in control at 7600rpm, I will not consider using one.
The next time I yank these damn heads off, I'm stuffing Ti valves in both sides, like I had intended to do several years ago, but was talked out of doing so....
07-03-2015, 01:22 PM
#129
Team Owner
Forgive my ignorance as I am very new to the LS7 and there is a lot of reading for me to do in this section....but could the failure issues be more associated with cars that are being spun past 7000 rpms? It's crazy that some motors have 50k or more miles and no issues and then others go south with less that 15k on them.
07-03-2015, 01:36 PM
#131
Le Mans Master
The thing is with cars with higher mileage, very few of those people are checking. So while they haven't dropped a valve yet, I would be surprised if many, or any of them are in spec guide wise. I think that leads more towards variation in the valves, were some on the thicker side of wall thickness can withstand more of a beating, and those unlucky cars with thinner valves get the heads beat off.
07-03-2015, 01:43 PM
#132
Team Owner
One of my friends here, CPR customer had a radial crack forming around the base of one of the exhaust valves when he pulled his heads. That is the closest to failure I've seen a car. You could see the crack going about 1/2 way around the head of the valve. Guides were 3-4x the service limit. There is variation in all parts made. Unless you pull the valves and do some sort of x-ray/ultrasonic depth/etc to measure wall thickness and inspect all the valves, really no way to tell if you have valves with good solid thickness or lack of defects.
07-03-2015, 02:12 PM
#133
Le Mans Master
One of my friends here, CPR customer had a radial crack forming around the base of one of the exhaust valves when he pulled his heads. That is the closest to failure I've seen a car. You could see the crack going about 1/2 way around the head of the valve. Guides were 3-4x the service limit. There is variation in all parts made. Unless you pull the valves and do some sort of x-ray/ultrasonic depth/etc to measure wall thickness and inspect all the valves, really no way to tell if you have valves with good solid thickness or lack of defects.
Also, met Joe (CPR) when I lived in Phoenix. Did some brake work on my GS. Great guy and great shop.
07-03-2015, 05:58 PM
#134
Drifting
I'm really torn on what to do with mine when it gets to CA. Part of me wants to just get it to AHP to get done right and part of me says to leave it be. I have never been hard on my vehicles and maintain them well....I did get a GMMGP ( GM Major Guard Package ) good for 4 years from the dealer I just bought the car from.
Also, met Joe (CPR) when I lived in Phoenix. Did some brake work on my GS. Great guy and great shop.
Also, met Joe (CPR) when I lived in Phoenix. Did some brake work on my GS. Great guy and great shop.
07-06-2015, 04:38 PM
#135
Intermediate
Usually its very difficult to control a SS valve train past 7000rpm. Up to 7000 is a snap just so long as your not trying to control 120g+ solid stem valves. Putting steal intakes in an LS7 is just crazy as far as I am concerned. I see heads sold that way but refuse to do it myself. The intake is far to heavy to control up to 7000rpm.
07-06-2015, 04:48 PM
#136
Intermediate
Thanks for that respond Darin.
I really don't want to belabor the same question, but can you provide some more detail on what it is you find, or have seen with respect to hollow stemmed exh valve problems? What exactly does "less than favorable" mean? Other than the most obvious, PTVC, I'd like to know what else can, or does happen.
With the exception of some older Ford engines, this LS7 is the first engine I've screwed with that uses these valves on the exh.
Controlling this valve train to 7000 isn't the concern, it's the over revs. There are some, myself included, who want a good 600-800rpm over fuel cutoff speed for these situations (I have personally seen 7600rpm twice now). Until someone shows me verified sprin rig results of a 95g valve staying in control at 7600rpm, I will not consider using one.
The next time I yank these damn heads off, I'm stuffing Ti valves in both sides, like I had intended to do several years ago, but was talked out of doing so....
I really don't want to belabor the same question, but can you provide some more detail on what it is you find, or have seen with respect to hollow stemmed exh valve problems? What exactly does "less than favorable" mean? Other than the most obvious, PTVC, I'd like to know what else can, or does happen.
With the exception of some older Ford engines, this LS7 is the first engine I've screwed with that uses these valves on the exh.
Controlling this valve train to 7000 isn't the concern, it's the over revs. There are some, myself included, who want a good 600-800rpm over fuel cutoff speed for these situations (I have personally seen 7600rpm twice now). Until someone shows me verified sprin rig results of a 95g valve staying in control at 7600rpm, I will not consider using one.
The next time I yank these damn heads off, I'm stuffing Ti valves in both sides, like I had intended to do several years ago, but was talked out of doing so....
07-07-2015, 01:31 AM
#137
Valve seals
Great info Darin . Thanks for taking the time.
You said along with removing the spring from the seals you also slit the seal to allow more oil on the race heads . Would you recommend this for a street car and would you discribe how you do that.
Thanks
You said along with removing the spring from the seals you also slit the seal to allow more oil on the race heads . Would you recommend this for a street car and would you discribe how you do that.
Thanks
07-10-2015, 10:48 PM
#140
Burning Brakes
Any Hint on the Heads you would lean towards...?