[Z06] Have any "fixed heads" failed ?
09-02-2015, 11:32 AM
#161
Former Vendor
Member Since: Aug 2005
Location: Lewisville TX
Posts: 16,898
Received 407 Likes
on
301 Posts
St. Jude Donor '03-'04-'05-'06-'07-'08-'09-'10-'11-'12-'13
Thank you very much for your candid reply.
I have the PRC265 heads(Ti intakes, SS exhaust, dual springs) using the original GM rocker arms, no milling and using GM head gaskets, with 21,500 miles on them. Everything else on my engine is stock. No leaks, no broken springs and it put out 453.23 rwhp and 437.52 lb-ft(SAE) on your dyno on an August morning that was 101.17 degrees in your dyno room. On another dyno(ambient 91.82 degrees in their shop) it put out 468.97 rwhp and 439.13 lb-ft but that was on STD, not SAE correction factor. I understand that the STD normally runs around 3% higher than SAE, so both dyno's measured very close to one another.
That's a little more horsepower than the ~445rwhp most stock LS7's put out, so I gained some horsepower(even though that's not the reason I changed out my heads).
I guess I lucked out with my aftermarket heads.
I have the PRC265 heads(Ti intakes, SS exhaust, dual springs) using the original GM rocker arms, no milling and using GM head gaskets, with 21,500 miles on them. Everything else on my engine is stock. No leaks, no broken springs and it put out 453.23 rwhp and 437.52 lb-ft(SAE) on your dyno on an August morning that was 101.17 degrees in your dyno room. On another dyno(ambient 91.82 degrees in their shop) it put out 468.97 rwhp and 439.13 lb-ft but that was on STD, not SAE correction factor. I understand that the STD normally runs around 3% higher than SAE, so both dyno's measured very close to one another.
That's a little more horsepower than the ~445rwhp most stock LS7's put out, so I gained some horsepower(even though that's not the reason I changed out my heads).
I guess I lucked out with my aftermarket heads.
I have seen stock dyno numbers range from 425 rwhp and 474. That is a huge range for what ever reason but if you wanted to do an average 445-458 rwhp is about on average. My 2008 Z06 put down 463 rwhp bone stock with no changes and 26k miles on it. The highest dyno I did was on a 2007 with zero changes and 8k miles on the clock after a handful of track day events.
Yes STD numbers always read higher and I am not sure why shops use it other than to give a high number. Factory uses SAE correction standards so we do as well.
09-02-2015, 12:25 PM
#162
Melting Slicks
It's like anything on a modified car. Nothing lasts for ever. Don't think because you have a head that is "fixed" that it would go 100,000 miles without touching it. By making a blanket statement saying all is well and good.....then you run into someone that has a 0.750" lift cam, 13.5:1 compression and a 300 shot of nitrous thinking they can go years and thousands of miles on end without working on it.
Sure if you did the correct work on stock heads on a completely stock car they should last you years of trouble free driving. Not knowing your (or everyone on here) combo I can not make that statement.
Does that explain it a little better?
Sure if you did the correct work on stock heads on a completely stock car they should last you years of trouble free driving. Not knowing your (or everyone on here) combo I can not make that statement.
Does that explain it a little better?
09-02-2015, 12:54 PM
#163
Team Owner
I have seen stock dyno numbers range from 425 rwhp and 474. That is a huge range for what ever reason but if you wanted to do an average 445-458 rwhp is about on average. My 2008 Z06 put down 463 rwhp bone stock with no changes and 26k miles on it. The highest dyno I did was on a 2007 with zero changes and 8k miles on the clock after a handful of track day events.
Yes STD numbers always read higher and I am not sure why shops use it other than to give a high number. Factory uses SAE correction standards so we do as well.
Yes STD numbers always read higher and I am not sure why shops use it other than to give a high number. Factory uses SAE correction standards so we do as well.
You have dyno'ed from 425 to 474. I don't believe that there is that much of a spread in horsepower from the engines as built by GM, so there must be other factors that are causing the wide range of readings on a chassis dyno.
I've seen one chassis dyno run on a LS7 where absolutely no changes were made to the engine or tune, yet a 10 minute later pull, resulted in a 23 rwhp increase.
That's why I asked about the ambient temp changes and my horsepower results on your dyno. We know that the ECM starts pulling timing at 89 degrees(I believe that's the number) IAT, and as the IAT increases the ECM pulls even more timing, so at 101 degrees IAT my engine should read lower horsepower than if the IAT was 80 degrees. Am I correct?
Then you get into the ECM pulling timing as the coolant starts going above 213 degrees(I think that's the starting number). That would decrease the horsepower also, correct?
The SAE correction factor doesn't get into those variables, does it?
I believe that most of the people in this tread are asking about getting their heads fixed for reliability( by not dropping a valve on their stock engine), not asking about how much horsepower they can get using radical cams, spinning to 7,500 RPM's, etc. so throwing those variables in the pot, isn't answering their questions.
Last edited by JoesC5; 09-02-2015 at 01:25 PM.
09-02-2015, 02:14 PM
#164
Former Vendor
Member Since: Aug 2005
Location: Lewisville TX
Posts: 16,898
Received 407 Likes
on
301 Posts
St. Jude Donor '03-'04-'05-'06-'07-'08-'09-'10-'11-'12-'13
I edited my post after you quoted it and asked a question about dyno readings at different ambient temps.
You have dyno'ed from 425 to 474. I don't believe that there is that much of a spread in horsepower from the engines as built by GM, so there must be other factors that are causing the wide range of readings on a chassis dyno.
I've seen one chassis dyno run on a LS7 where absolutely no changes were made to the engine or tune, yet a 10 minute later pull, resulted in a 23 rwhp increase.
That's why I asked about the ambient temp changes and my horsepower results on your dyno. We know that the ECM starts pulling timing at 89 degrees(I believe that's the number) IAT, and as the IAT increases the ECM pulls even more timing, so at 101 degrees IAT my engine should read lower horsepower than if the IAT was 80 degrees. Am I correct?
Then you get into the ECM pulling timing as the coolant starts going above 213 degrees(I think that's the starting number). That would decrease the horsepower also, correct?
The SAE correction factor doesn't get into those variables, does it?
I believe that most of the people in this tread are asking about getting their heads fixed for reliability( by not dropping a valve on their stock engine), not asking about how much horsepower they can get using radical cams, spinning to 7,500 RPM's, etc. so throwing those variables in the pot, isn't answering their questions.
You have dyno'ed from 425 to 474. I don't believe that there is that much of a spread in horsepower from the engines as built by GM, so there must be other factors that are causing the wide range of readings on a chassis dyno.
I've seen one chassis dyno run on a LS7 where absolutely no changes were made to the engine or tune, yet a 10 minute later pull, resulted in a 23 rwhp increase.
That's why I asked about the ambient temp changes and my horsepower results on your dyno. We know that the ECM starts pulling timing at 89 degrees(I believe that's the number) IAT, and as the IAT increases the ECM pulls even more timing, so at 101 degrees IAT my engine should read lower horsepower than if the IAT was 80 degrees. Am I correct?
Then you get into the ECM pulling timing as the coolant starts going above 213 degrees(I think that's the starting number). That would decrease the horsepower also, correct?
The SAE correction factor doesn't get into those variables, does it?
I believe that most of the people in this tread are asking about getting their heads fixed for reliability( by not dropping a valve on their stock engine), not asking about how much horsepower they can get using radical cams, spinning to 7,500 RPM's, etc. so throwing those variables in the pot, isn't answering their questions.
No the dyno can not adjust for what the computer does....all it can do is adjust for what it sees as air temp / humidity / and elevation.
on a stock car yes it will start pulling timing at approx 86 degrees and it varies with cylinder load on where it is how much....under WOT it can pull up to 8 degree's of timing by 122 degree air intake temp.
Now that is just that table.. You also have to take into account the modifier tables that go along with that. Some will make it remove less during different parts of the RPM range than others.
ECT temp is also one, and it will start removing timing around 212 degree's ....again modifier tables with that as well. This table can also add timing. It will add in a degree as hot as 158 and can add as much as 18 degrees of timing at -4 ECT.
You also have the AFR table that will either remove or add timing depending again on RPM and A/F .....in this table above say 4400 RPM it can add 2 to 5 degree's of timing.
I guess what I am saying is that you can not just look at one table and say this is the only thing that is effecting timing.
Yes for sure conditions do play a roll into what the engine can produce on it. I generally try and make sure water temp is at normal range (190-205) and oil temp is 160-180 and air temp is close to the dyno room which can vary from 60-101 degree's depending on the weather outside.
You add all of that up and it is not going to effect that car 50 hp between my highest and lowest run. Yes it can affect 2-8 hp if you keep the cars in a 'normal' temp range but not that much.
To throw more into all of this you have cat overtemp fueling protection when it thinks the cats are running hot and it starts changing A/F by up to 1 full point.
Honestly it is amazing the cars stay that close pull after pull after pull.
ZR1....different story all together.
09-02-2015, 03:12 PM
#165
Maybe on my next trip to my shop I'll have them do the valve guide test and see how they measure.
I am on WCCH Stage 2 OEM heads w/ bronze guides, OEM Ti intake, and SS exhaust valves, mild cam.
It has been about 2.5 years, probably about 15000 miles, 100+ autocross runs, 10 hours of track time (7 HPDEs). I am not shy about hitting the rev limiter (7100rpm). Honestly I don't even worry about it anymore. It should be interesting to see whether they're still within spec.
I am on WCCH Stage 2 OEM heads w/ bronze guides, OEM Ti intake, and SS exhaust valves, mild cam.
It has been about 2.5 years, probably about 15000 miles, 100+ autocross runs, 10 hours of track time (7 HPDEs). I am not shy about hitting the rev limiter (7100rpm). Honestly I don't even worry about it anymore. It should be interesting to see whether they're still within spec.
09-02-2015, 04:06 PM
#166
Le Mans Master
I have seen stock dyno numbers range from 425 rwhp and 474. That is a huge range for what ever reason but if you wanted to do an average 445-458 rwhp is about on average. My 2008 Z06 put down 463 rwhp bone stock with no changes and 26k miles on it. The highest dyno I did was on a 2007 with zero changes and 8k miles on the clock after a handful of track day events.
Yes STD numbers always read higher and I am not sure why shops use it other than to give a high number. Factory uses SAE correction standards so we do as well.
Yes STD numbers always read higher and I am not sure why shops use it other than to give a high number. Factory uses SAE correction standards so we do as well.
09-02-2015, 04:53 PM
#167
Former Vendor
Member Since: Aug 2005
Location: Lewisville TX
Posts: 16,898
Received 407 Likes
on
301 Posts
St. Jude Donor '03-'04-'05-'06-'07-'08-'09-'10-'11-'12-'13
I had 69k miles on the car when I sold it. I did check them and I had a set of heads here ready to go on it, but baby came and I sold the car. they did show increased amounts of wear on a quick check but were not as bad as others I had seen. Given it's little track use I didn't worry about it to much.
09-02-2015, 05:46 PM
#168
Team Owner
Maybe on my next trip to my shop I'll have them do the valve guide test and see how they measure.
I am on WCCH Stage 2 OEM heads w/ bronze guides, OEM Ti intake, and SS exhaust valves, mild cam.
It has been about 2.5 years, probably about 15000 miles, 100+ autocross runs, 10 hours of track time (7 HPDEs). I am not shy about hitting the rev limiter (7100rpm). Honestly I don't even worry about it anymore. It should be interesting to see whether they're still within spec.
I am on WCCH Stage 2 OEM heads w/ bronze guides, OEM Ti intake, and SS exhaust valves, mild cam.
It has been about 2.5 years, probably about 15000 miles, 100+ autocross runs, 10 hours of track time (7 HPDEs). I am not shy about hitting the rev limiter (7100rpm). Honestly I don't even worry about it anymore. It should be interesting to see whether they're still within spec.
09-02-2015, 06:37 PM
#169
I don't have measurements of when they were new, so I can't measure wear, but there may be some ballpark estimates on what a new set of bronze guides should be at and we can see whether they're still in spec. The car doesn't have much track time on it, but it isn't a garage queen either.
09-02-2015, 07:39 PM
#170
welcome to my world - have a beer
so far it sounds like American heritage heads, YT rockers, powdered metal guides, tumble coated titanium intakes, and hollow SS exhaust valves is the way to go...ANNNDDD THHEEENNN have them pulled of every 6 months to check (~$800 bucks) if they are bad tack on 3-4k for new everything. not great but better than exotics maintenancealthough in the meantime im going nuts polling the whole member base for a better solution...after 3 days of nearly solid research....I think this is kind of end all solution to having the car for a while....everything else that falls under maintenance stuff handle by a good race shop or yourself.
Last edited by univerz06; 09-02-2015 at 07:46 PM.
09-02-2015, 08:05 PM
#171
Safety Car
welcome to my world - have a beer so far it sounds like American heritage heads, YT rockers, powdered metal guides, tumble coated titanium intakes, and hollow SS exhaust valves is the way to go...ANNNDDD THHEEENNN have them pulled of every 6 months to check (~$800 bucks) if they are bad tack on 3-4k for new everything. not great but better than exotics maintenance
although in the meantime im going nuts polling the whole member base for a better solution...after 3 days of nearly solid research....I think this is kind of end all solution to having the car for a while....everything else that falls under maintenance stuff handle by a good race shop or yourself.
so far it sounds like American heritage heads, YT rockers, powdered metal guides, tumble coated titanium intakes, and hollow SS exhaust valves is the way to go...ANNNDDD THHEEENNN have them pulled of every 6 months to check (~$800 bucks) if they are bad tack on 3-4k for new everything. not great but better than exotics maintenancealthough in the meantime im going nuts polling the whole member base for a better solution...after 3 days of nearly solid research....I think this is kind of end all solution to having the car for a while....everything else that falls under maintenance stuff handle by a good race shop or yourself.
09-02-2015, 08:11 PM
#172
Team Owner
welcome to my world - have a beer so far it sounds like American heritage heads, YT rockers, powdered metal guides, tumble coated titanium intakes, and hollow SS exhaust valves is the way to go...ANNNDDD THHEEENNN have them pulled of every 6 months to check (~$800 bucks) if they are bad tack on 3-4k for new everything. not great but better than exotics maintenance.
so far it sounds like American heritage heads, YT rockers, powdered metal guides, tumble coated titanium intakes, and hollow SS exhaust valves is the way to go...ANNNDDD THHEEENNN have them pulled of every 6 months to check (~$800 bucks) if they are bad tack on 3-4k for new everything. not great but better than exotics maintenance.
09-02-2015, 08:11 PM
#173
the other problems people have seem to come from adding HP (cause 505 isnt enough??) , cams, all this other stuff....the only other thing I think one could consider required is forged piston heads to prevent cylinder 7 from vaporizing...but even then...that seems like something caused from tuning the engine to run lean.
if tracking some oil stuff seems good (researching now)
intake as long as not forced induction /exhaust stuff doesnt seem to lead to major issues
the biggest issue Ive seen thus far is random engine death from valve/ cylinder head failure - seems some die from lack of oil under sustained turns.
if tracking some oil stuff seems good (researching now)
intake as long as not forced induction /exhaust stuff doesnt seem to lead to major issues
the biggest issue Ive seen thus far is random engine death from valve/ cylinder head failure - seems some die from lack of oil under sustained turns.
09-02-2015, 08:12 PM
#174
thats just a type of powdered metal - no offense to the developers but it seems like a materials engineering pet project/ is sort of gimmicky for something id consider a wear part....almost seems best to go with bronze guide for that reason actually
Last edited by univerz06; 09-02-2015 at 08:16 PM. Reason: a word
09-02-2015, 08:20 PM
#175
Supporting Vendor
Member Since: Sep 2013
Location: Harbor City California
Posts: 2,820
Received 1,015 Likes
on
534 Posts
MoldStar90 has been an F1/Indy car secret for 10+ years. Heavily tested and heavily proven as a solid material for the intended application.
All valve guides are a wear item/part (on any and every engine, not just the LS7).
We had some testing conducted by a third party source some time ago. The testing compared PM, Bronze and our MoldStar90 guides. Testing repeatedly showed that not only is MoldStar90 harder than Bronze (manganese or other) but it has better heat transferring ability as well. Another thing is MoldStar90 work hardens over time so unlike bronze it will get stronger the longer it is used.
09-02-2015, 08:21 PM
#176
Team Owner
You've seen the results of the guide hardness tests that AHP posted, yes? Compared stock, bronze, AHP's PM, and MS90. MS90 is slick stuff.
09-02-2015, 09:03 PM
#177
Pro
welcome to my world - have a beer so far it sounds like American heritage heads, YT rockers, powdered metal guides, tumble coated titanium intakes, and hollow SS exhaust valves is the way to go...ANNNDDD THHEEENNN have them pulled of every 6 months to check (~$800 bucks) if they are bad tack on 3-4k for new everything. not great but better than exotics maintenance
although in the meantime im going nuts polling the whole member base for a better solution...after 3 days of nearly solid research....I think this is kind of end all solution to having the car for a while....everything else that falls under maintenance stuff handle by a good race shop or yourself.
so far it sounds like American heritage heads, YT rockers, powdered metal guides, tumble coated titanium intakes, and hollow SS exhaust valves is the way to go...ANNNDDD THHEEENNN have them pulled of every 6 months to check (~$800 bucks) if they are bad tack on 3-4k for new everything. not great but better than exotics maintenancealthough in the meantime im going nuts polling the whole member base for a better solution...after 3 days of nearly solid research....I think this is kind of end all solution to having the car for a while....everything else that falls under maintenance stuff handle by a good race shop or yourself.
09-02-2015, 10:26 PM
#178
NO MoldStar90 is not a type of powder metal guide.
MoldStar90 has been an F1/Indy car secret for 10+ years. Heavily tested and heavily proven as a solid material for the intended application.
All valve guides are a wear item/part (on any and every engine, not just the LS7).
We had some testing conducted by a third party source some time ago. The testing compared PM, Bronze and our MoldStar90 guides. Testing repeatedly showed that not only is MoldStar90 harder than Bronze (manganese or other) but it has better heat transferring ability as well. Another thing is MoldStar90 work hardens over time so unlike bronze it will get stronger the longer it is used.
MoldStar90 has been an F1/Indy car secret for 10+ years. Heavily tested and heavily proven as a solid material for the intended application.
All valve guides are a wear item/part (on any and every engine, not just the LS7).
We had some testing conducted by a third party source some time ago. The testing compared PM, Bronze and our MoldStar90 guides. Testing repeatedly showed that not only is MoldStar90 harder than Bronze (manganese or other) but it has better heat transferring ability as well. Another thing is MoldStar90 work hardens over time so unlike bronze it will get stronger the longer it is used.
well damn....10/10
it lasts way longer then im assuming?? at the moment im trying to get an annual budget for maintenance together. Currently it includes head check every 6 months replace if needed... im willing to eat the cost of the hardcore material if its gunna mean significant savings/peace of mind over time.
Last edited by univerz06; 09-02-2015 at 11:29 PM.
09-02-2015, 10:32 PM
#179
wont lie...I glanced at the start of all this and thought its too good to be true....but 3 days later i see the name AH everywhere followed by phrases like "none have failed yet" and they just responded to a post...soooo its probably safe to assume its real. they also got my bizz with that when the time comes...wich is bitter sweet because the budget feels like its attached to a rocket at this point....someone let me get a student discount please
Last edited by univerz06; 09-02-2015 at 11:32 PM.
09-03-2015, 09:14 AM
#180
Team Owner
wont lie...I glanced at the start of all this and thought its too good to be true....but 3 days later i see the name AH everywhere followed by phrases like "none have failed yet" and they just responded to a post...soooo its probably safe to assume its real. they also got my bizz with that when the time comes...wich is bitter sweet because the budget feels like its attached to a rocket at this point....someone let me get a student discount please
