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C6 Corvette ZR1 & Z06General info about GM’s Corvette Supercar, LS9 Corvette Technical Info, Performance Upgrades, Suspension Setup for Street or Track
Wow, that first link you posted is familiar! I wonder if he purchased them at the same time as me.
Originally Posted by '06 Quicksilver Z06
How?
The heads described in this thread are aftermarket heads with failed aftermarket intake valves.
"The fix" utilizes the stock heads, and involves "fixing" what are believed to be flaws in the OEM stock heads.
At any rate, best of luck to the OP of this thread as there have been a few cases of described issues in those particular heads now.
I can remember one owner of these heads in particular making comments and getting all up in arms about grinder marks on another set of competing heads in here.
These incident reports below make minimal grinder marks comparatively minor.
What route did you ultimately take to fix your issue? Was it concluded to be a valve issue or something else?
Looks like you weren't so lucky since I see a chunk of valve guide I'm guessing you lost a valve and blew the motor?
I'm certainly not blaming PRC/TSP since it's not 100% clear what the real issue is. Even if it's a valve issue the supplier is ultimately to blame but hopefully TSP can help me get it going without too much pocket book damage. I looked at the cost of a set of new manley Ti valves and they were almost a grand for 8.
Originally Posted by andy82
Me. I had the California BAR do an investigation. Just FYI: It was not TSP's fault, the heads geometry and installation was fine.
Well knowing seat load would be a data point, but not what I was looking for and it will not tell you where you are with coil bind. For the tip to break off like that, I'm leaning towards a defect with the valve, but if your under .050" from bind, that could be as bad, if not worse than bottoming out a lifter's plunger. It could be just enough to push the failure point off the ledge, so to speak…
If you are running the Comp 26926 springs with Ti retainers, you are running some really good springs. They are what I have been using. They were not my first choice, but I couldn’t find a PAC spring (my usual go to spring) with the same rate and distance to coil bind that could use with my valve lift, so I gave them a whirl. After 5000 miles of use, seated and open loads were within 2 pounds of spec. I was pleasantly surprised. If installed at 1.835”, you should have 129psi on the seat and 470psi at .675”. At an installed height if 1.835”, you can run a valve lift of .675” and will be .060” away from coil bind – which is perfect. If you are under .050”, or over .100”, you can have serious problems.
For anyone that's curious - this is what the hardened tips look like prior to being pressed into the valve. In all of these situations it looks like the knurled section separated from the top hat portion via a clean break/crack.
I'm using the PRC spring set which according to their description has been tested in excess of .700" lift but they advertise a .675 maximum lift. I don't think which brand they've re-branded though. My lift is .649/.660.
I'm leaning towards valve failure as well and I think I would feel pretty good about simply replacing all the intake valves with a different brand or ones that use lash caps.
Originally Posted by Michael_D
Well knowing seat load would be a data point, but not what I was looking for and it will not tell you where you are with coil bind. For the tip to break off like that, I'm leaning towards a defect with the valve, but if your under .050" from bind, that could be as bad, if not worse than bottoming out a lifter's plunger. It could be just enough to push the failure point off the ledge, so to speak…
If you are running the Comp 26926 springs with Ti retainers, you are running some really good springs. They are what I have been using. They were not my first choice, but I couldn’t find a PAC spring (my usual go to spring) with the same rate and distance to coil bind that could use with my valve lift, so I gave them a whirl. After 5000 miles of use, seated and open loads were within 2 pounds of spec. I was pleasantly surprised. If installed at 1.835”, you should have 129psi on the seat and 470psi at .675”. At an installed height if 1.835”, you can run a valve lift of .675” and will be .060” away from coil bind – which is perfect. If you are under .050”, or over .100”, you can have serious problems.
Yes, they mentioned that they've experienced this issue before and their new valves have lash caps instead of these hardened tips. I don't know what that means for me just yet but I'll have to wait and see.
Yes, they mentioned that they've experienced this issue before and their new valves have lash caps instead of these hardened tips. I don't know what that means for me just yet but I'll have to wait and see.
Hmmm..........interesting. I've had mine for about a year and a half now, purchase late winter in 2013 but only about 3000 miles since the install. I'm sure they'll make it right. Curious, how long have you heard the noice, how quickly and long did it take to get as you said 'progessively' worse ??
When I first installed the heads everything it was pretty quiet. In the last 500 miles or so I started to hear a bit of a sewing machine sound and I had to ask myself if it was normal or not. I started thinking to myself that maybe it's because I always had the radio on and never paid much attention to it. Within the last 60 miles I started to notice the noise was getting louder and it was enough for me to escalate my thought of normal/sewing machine sound to "I have a problem". When the upper half of the pressed in cap breaks off I don't think it adds much of a noise (maybe a little if you pay attention). When the the second portion of the pressed in cap (splined piece visible on my finger in the pic) breaks off then things accelerate real fast. You probably only have 20 miles from "Am I imagining it?" to "There's something really wrong".
Originally Posted by RedZ4me
Hmmm..........interesting. I've had mine for about a year and a half now, purchase late winter in 2013 but only about 3000 miles since the install. I'm sure they'll make it right. Curious, how long have you heard the noice, how quickly and long did it take to get as you said 'progessively' worse ??
thanks..........when my heads were installed, they sounded pretty much the same as stock........LS motors seem to not be the quietest, even after I added the Trunion upgrade...........I still have the light ticking from about 1500-2000 rpms, especially when the oil is hotter. Never got better or worst, just always there.....Not loud, just there and with all the LS7 crap, seems every drive I just listen to noises
What route did you ultimately take to fix your issue? Was it concluded to be a valve issue or something else?
Looks like you weren't so lucky since I see a chunk of valve guide I'm guessing you lost a valve and blew the motor?
I'm certainly not blaming PRC/TSP since it's not 100% clear what the real issue is. Even if it's a valve issue the supplier is ultimately to blame but hopefully TSP can help me get it going without too much pocket book damage. I looked at the cost of a set of new manley Ti valves and they were almost a grand for 8.
Actually I was REALLY lucky, although this looks bad the car was just pulled into the garage and was at idle. I heard a noise and turned it off immediately. No damage to the engine.
The California BAR association determined a valve issue were the hardened caps were not pressed into the valves all the way and as a result the tips broke off.
Ergo: Bad batch of valves. Heads (TSP) or install was not to blame.
That's an interesting conclusion since the pics you posted show that the hardened tip cracked and separated from the bottom half of the tip. Look at the pic I posted of the hardened tips and look at the tips on the pic you posted.
Originally Posted by andy82
Actually I was REALLY lucky, although this looks bad the car was just pulled into the garage and was at idle. I heard a noise and turned it off immediately. No damage to the engine.
The California BAR association determined a valve issue were the hardened caps were not pressed into the valves all the way and as a result the tips broke off.
Ergo: Bad batch of valves. Heads (TSP) or install was not to blame.
I have the noise recorded on my phone (m4a format). I can text it to you if you PM your number. It makes me cringe listening to it knowing how close it was to dropping that valve.
I have the noise recorded on my phone (m4a format). I can text it to you if you PM your number. It makes me cringe listening to it knowing how close it was to dropping that valve.
08-11-2014, 01:00 PM
I'm guessing you lost a valve and blew the motor? 
