[Z06] Maybe The PRC Heads Are NOT The Answer To Guide Wear
10-03-2013, 12:33 PM
#1
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St. Jude Donor '08
Maybe The PRC Heads Are NOT The Answer To Guide Wear
We installed a complete set of PRC heads on a customers car back in March, almost 7,000 miles ago. It was on a 2006 Z06 and the customer was worried about the LS7 guide wear issue so he elected to go with the PRC heads to avoid the down time of having a good set built by WCCH. The complete heads were put on the car, along with a baby smog cam, new lifters, gaskets, bolts etc.
The car returned this week with a loud ticking noise that originally sounded like a lifter. After closer examination, we found that all of the intake valve to guide clearances are extremely out of spec. We have measurements from .010"-.019" across the board. Keep in mind that GM spec is .0037" so we are talking waaaaaaaaaaaaaaay out of spec. The exhaust measurements are all close to spec or slightly less, but the intakes are scary. You can move all of them without even removing the valve springs.
This particular one has about .016" play in EACH direction
The car returned this week with a loud ticking noise that originally sounded like a lifter. After closer examination, we found that all of the intake valve to guide clearances are extremely out of spec. We have measurements from .010"-.019" across the board. Keep in mind that GM spec is .0037" so we are talking waaaaaaaaaaaaaaay out of spec. The exhaust measurements are all close to spec or slightly less, but the intakes are scary. You can move all of them without even removing the valve springs.
This particular one has about .016" play in EACH direction
10-03-2013, 12:37 PM
#2
Melting Slicks
We installed a complete set of PRC heads on a customers car back in March, almost 7,000 miles ago. It was on a 2006 Z06 and the customer was worried about the LS7 guide wear issue so he elected to go with the PRC heads to avoid the down time of having a good set built by WCCH. The complete heads were put on the car, along with a baby smog cam, new lifters, gaskets, bolts etc.
The car returned this week with a loud ticking noise that originally sounded like a lifter. After closer examination, we found that all of the intake valve to guide clearances are extremely out of spec. We have measurements from .010"-.019" across the board. Keep in mind that GM spec is .0037" so we are talking waaaaaaaaaaaaaaay out of spec. The exhaust measurements are all close to spec or slightly less, but the intakes are scary. You can move all of them without even removing the valve springs.
This particular one has about .016" play in EACH direction
The car returned this week with a loud ticking noise that originally sounded like a lifter. After closer examination, we found that all of the intake valve to guide clearances are extremely out of spec. We have measurements from .010"-.019" across the board. Keep in mind that GM spec is .0037" so we are talking waaaaaaaaaaaaaaay out of spec. The exhaust measurements are all close to spec or slightly less, but the intakes are scary. You can move all of them without even removing the valve springs.
This particular one has about .016" play in EACH direction
Round and round we go. Thanks Rich.
I don't know much about PRC heads. What kind of rockers are used? Valves? Guides?
Thanks
10-03-2013, 01:17 PM
#11
Safety Car
Its my car and the entire thing sucks ***!
I bought those heads with the best available parts to prevent future valve guide issues in the first place (my LS7 was fine) and now I'm screwed with double shipping, labor and all the other crap.
TSP only offered to send me new guides or send the heads back to them for rework, nothing else. After some consideration I decided to send them back and have them completely inspected because I don't want to be blamed again in 7K miles.
Last edited by andy82; 10-03-2013 at 01:22 PM.
10-03-2013, 01:38 PM
#14
Team Owner
Seen a few WCCH heads come back too with guide wear. I wonder if the 1.8 rockers are just too much.
10-03-2013, 01:44 PM
#16
Safety Car
10-03-2013, 01:55 PM
#17
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St. Jude Donor '08
Stainless intake and exhaust.
Yes, they were in the .002"-.003" range.
I guess that we are removing the heads to send back to TSP for inspection. Apparently they were only going to send the customer a new bag of guides and he would have to pay R/R of the heads and a local machine shop to swap the guides over. He wasn't thrilled about that so they offered to inspect the heads if he paid for all labor, gaskets, fluids and the shipping
How gracious of them 
He is being told that having the lifter preload at ~1.25 turns on the rocker bolts caused the issue so they are not standing behind anything.
10-03-2013, 01:58 PM
#18
Melting Slicks
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Wow. So aftermarket rockers can't be the culprit for this one.
Who's to say the WCCH heads with stock rockers can't wear, too?
Who's to say the WCCH heads with stock rockers can't wear, too?
Last edited by TheDingo; 10-03-2013 at 02:01 PM.
10-03-2013, 02:04 PM
#20
Melting Slicks
Nope. Going back to the last thread I am thinking the bronze guides cant stand up to the 1.8 rockers.
This is my point with all of this, introduce another element in trying to fix the problem and now you are left with more questions when it fails or shows wear again. Was it the guides? The rockers? The guide geometry? The SS valves? The springs? Oil starvation? (That's an old one I know)
Sorry to the OP for this mess. I know if it were me I would be really angry trying to fix the problem based on "experts" and spending a lot of money only to be back in the same boat again. Hope it gets sorted out without you having to open your wallet again.
This is my point with all of this, introduce another element in trying to fix the problem and now you are left with more questions when it fails or shows wear again. Was it the guides? The rockers? The guide geometry? The SS valves? The springs? Oil starvation? (That's an old one I know)
Sorry to the OP for this mess. I know if it were me I would be really angry trying to fix the problem based on "experts" and spending a lot of money only to be back in the same boat again. Hope it gets sorted out without you having to open your wallet again.