[Z06] Maybe The PRC Heads Are NOT The Answer To Guide Wear
10-03-2013, 03:01 PM
#41
The intakes are pretty large, bigger than any other LS valve out there. Moving from Ti to SS is pretty significant. It is possible that this size valve doesn't do well with SS on this valve train.
From PRC's site - http://www.texas-speed.com/p-1236-pr...cnc-heads.aspx
If you are going to run the stainless steel intake valves, we recommend limiting total valve lift to no more than .616" due to the weight of the intake valve. Upgrading to the hollow-stem intake valve will shed significant intake valve weight and allow for additional lift. The titanium intake valves will be the lightest choice of the three choices and offer the best lift possible!
What were the specs on the cam?
10-03-2013, 03:22 PM
#42
Safety Car
The intakes are pretty large, bigger than any other LS valve out there. Moving from Ti to SS is pretty significant. It is possible that this size valve doesn't do well with SS on this valve train.
From PRC's site - http://www.texas-speed.com/p-1236-pr...cnc-heads.aspx
If you are going to run the stainless steel intake valves, we recommend limiting total valve lift to no more than .616" due to the weight of the intake valve. Upgrading to the hollow-stem intake valve will shed significant intake valve weight and allow for additional lift. The titanium intake valves will be the lightest choice of the three choices and offer the best lift possible!
What were the specs on the cam?
PRC 6-Bolt LS7 Cylinder Heads with Thicker Deck Surface
Will Work on Both Standard GM 4-Bolt & Aftermarket LSx / RHS 6-Bolt Style Engine Blocks
2.200"/1.59" Valves
PRC Double Spring Kit Complete With PRC Double
Springs, Titanium Retainers, Seats, & Seals
Completely Assembled & Setup To Your Specs
Available With Stainless Steel, Hollow-Stem, or Titanium Intake Valves
Extensive CNC and dyno testing has resulted in one of the most affordable and powerful LS7-based cylinder heads available! Flowing up to 35 CFM more than the stock GM LS7 head, the all-new PRC cylinder heads offer both unmatched power and airflow!
The PRC Small Bore LS7 cylinder heads are designed for both stroker, and stock cube applications with a 4.060"-4.100" bore. For bores larger than 4.100" bore checkout the PRC LS7 270cc & 285cc cylinder heads!
The PRC LS7 cylinder heads is available with standard stainless valves, hollow-stem intake, and titanium intake valves. If you are going to run the stainless steel intake valves, we recommend limiting total valve lift to no more than .616" due to the weight of the intake valve. Upgrading to the hollow-stem intake valve will shed significant intake valve weight and allow for additional lift. The titanium intake valves will be the lightest choice of the three choices and offer the best lift possible!
10-03-2013, 03:51 PM
#43
Melting Slicks
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Any takers on this one?? I think you guys are referring to people using castings that aren't OEM, different push rods or aftermarket rockers. Correct?
Last edited by TheDingo; 10-03-2013 at 03:54 PM.
10-03-2013, 03:57 PM
#44
I wonder if anyone knows where they started.
For example, guide to stem clearances on heads done by the shop which did yours are .00125-.00150 when they leave.
What I'm getting at is, since it is probably unknown by anyone in here as to what the stem to guide clearances started at on those heads, I'm wondering just how much "wear" that .002"-.003" you speak of represents.
For reference, anything from .0010-.0026 is the production spec for stem to guide clearance in the stock heads.
.0037" as mentioned earlier, is the service limit.
[/IMG]Last edited by '06 Quicksilver Z06; 10-03-2013 at 04:58 PM.
10-03-2013, 04:30 PM
#45
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If this was a valve guide material issue, you would see the crazy wear on the intake AND exhaust guides. The fact that you only see them on the intake side is an indication of something happening otherwise. We use the best valve guide material we can possibly find. That being said, we don't have control of how a customer's valvetrain is setup. We recently had a 30,000 mile set of heads arrive, & they were well within spec. I expect there is something causing this additional wear. There is something amiss if the car got a new cam one month prior to the issue popping up. The customer told one of our salesmen, John, today that he has put 7,000 miles on the cylinder heads. If this were a problem with material, I would expect that you would see the issue in a lot fewer miles, as well as on the intake and exhaust guides.
Jason already ok'd the heads to come back for valve guide replacement, so I'm not sure where the confusion is on us not trying to help.
It's unfortunate that the car is having issues, but one thing I must warn you. If you swap guides & put the heads right back on, whatever has caused these issues will no doubt cause it again. I would highly recommend checking your valvetrain. Considering that the valvetrain was upgraded one month prior to the issue, that raises a red flag for me.
We have used over 20,000 bronze guides in cylinder heads all over the world. Whenever someone ends up with bronze guide wear, it's typically a valvetrain issue. We sell a LOT of PRC LS7 cylinder heads, and we have not had one other issue reported with excessive wear on the bronze guides. If that were the case, you would see threads just like this one posted on multiple forums from multiple customers.
Let us know if you have any other questions or concerns.
Trevor
Texas Speed & Performance
Jason already ok'd the heads to come back for valve guide replacement, so I'm not sure where the confusion is on us not trying to help.
It's unfortunate that the car is having issues, but one thing I must warn you. If you swap guides & put the heads right back on, whatever has caused these issues will no doubt cause it again. I would highly recommend checking your valvetrain. Considering that the valvetrain was upgraded one month prior to the issue, that raises a red flag for me.
We have used over 20,000 bronze guides in cylinder heads all over the world. Whenever someone ends up with bronze guide wear, it's typically a valvetrain issue. We sell a LOT of PRC LS7 cylinder heads, and we have not had one other issue reported with excessive wear on the bronze guides. If that were the case, you would see threads just like this one posted on multiple forums from multiple customers.
Let us know if you have any other questions or concerns.
Trevor
Texas Speed & Performance
Last edited by Trevor @ Texas Speed; 10-03-2013 at 04:43 PM. Reason: more info
10-03-2013, 04:32 PM
#46
10-03-2013, 04:34 PM
#47
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Here's the link to the company that supplies our valve guides. Make no mistake there are a lot of cheap valve guides out there on the market. We use only the highest quality bronze available & even do random metallurgy tests.
A perfect example of this is we could buy bronze guides for well under $3 but we choose to use a higher quality bronze that costs us nearly $6 per guide!!
http://www.nbmmetals.com/
A perfect example of this is we could buy bronze guides for well under $3 but we choose to use a higher quality bronze that costs us nearly $6 per guide!!
http://www.nbmmetals.com/
10-03-2013, 04:35 PM
#48
Melting Slicks
Guys we use the best valve guide material we can possibly find. That being said we don't have control of how someones valvetrain is setup. We recently had a 30k mile set of heads arrive & they were fine. I expect there is something causing this additional wear.
Jason already ok'd the heads to come back for valve guide replacement so I'm not sure where the confusion is on us not trying to help.
It's unfortunate that the car is having issues, but one thing I must warn you. If you swap guides & put them right back on whatever has caused these issues will no doubt cause it again.
We have used over 20,000 bronze guides in cylinder heads all over the world. Whenever someone ends up with bronze guide wear it's usually a valvetrain issue.
Jason already ok'd the heads to come back for valve guide replacement so I'm not sure where the confusion is on us not trying to help.
It's unfortunate that the car is having issues, but one thing I must warn you. If you swap guides & put them right back on whatever has caused these issues will no doubt cause it again.
We have used over 20,000 bronze guides in cylinder heads all over the world. Whenever someone ends up with bronze guide wear it's usually a valvetrain issue.
10-03-2013, 04:44 PM
#49
Team Owner
Lifter preload in LS motors is set by pushrod length. Typically .040-.080". This can be equated to turns of the rocker arm bolts from zero preload based on the amount the rocker goes down per turn of the rocker arm bolt from a zero preload condition.
10-03-2013, 04:49 PM
#51
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10-03-2013, 04:51 PM
#52
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The valves in the customer's cylinder heads are titanium intakes, so there is not a valvetrain weight issue in that respect.
10-03-2013, 04:56 PM
#53
Team Owner
My valve train on my WWCH sounds the same as day one and they have over 16K miles and 9 track days
DH
10-03-2013, 04:56 PM
#54
Safety Car
We were told by the customer that they had 1.5 turns of the rocker bolt. This would equate to ~.120" of lifter pre-load, which is way too much. It doesn't sound like the person that assembled the valvetrain checked for proper lifter pre-load.
The valves in the customer's cylinder heads are titanium intakes, so there is not a valvetrain weight issue in that respect.
The valves in the customer's cylinder heads are titanium intakes, so there is not a valvetrain weight issue in that respect.
10-03-2013, 04:59 PM
#56
Melting Slicks
10-03-2013, 05:03 PM
#57
Safety Car
10-03-2013, 05:03 PM
#58
Melting Slicks
We were told by the customer that they had 1.5 turns of the rocker bolt. This would equate to ~.120" of lifter pre-load, which is way too much. It doesn't sound like the person that assembled the valvetrain checked for proper lifter pre-load.
The valves in the customer's cylinder heads are titanium intakes, so there is not a valvetrain weight issue in that respect.
The valves in the customer's cylinder heads are titanium intakes, so there is not a valvetrain weight issue in that respect.
10-03-2013, 05:08 PM
#59
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The problem with longer guides is it will kill flow if it extends further into the port. If it extends further up towards the springs, it will limit valve lift. The guide length has never been an issue for us or any other cylinder head porter or manufacturer. Again, the issue in question is only on the intake side. The guides for the intake and exhaust came out of the same box. If the guides are faulty, they would be bad on both the intake and exhaust.
10-03-2013, 05:10 PM
#60
Team Owner
