2002 GM CNC Ported Z06/LS6 Heads (INFO)
07-12-2002 | 11:06 AM
#1
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Joined: Nov 2001
Posts: 44,817
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From: Chicago, IL
2002 GM CNC Ported Z06/LS6 Heads (INFO) 2002 ZO6/LS6 Cylinder Heads - Bare and CNC Ported
First, several questions have been asked about the price difference and why there are two different part numbers for the 2001 and 2002 bare LS6 cylinder heads. One of the most important facts to know about GM part numbers is that
there are about four basic distinct styles of part numbers within the GM hierarchy(internal, industrial, service replacement, and racing), only two of these have any real concern to the typical consumer. One being service replacement part numbers, such as the 2001 and 2002 LS6 cylinder heads.
These parts have a very strict set of guidelines, as in zero tolerance from the engineering print and specification. Something as simple as tapping one threaded hole an additional 0.100" deeper will require a complete new set of prints, validation testing, and a new part number in the GM system. If a change is made in suppliers, even though the part is still being manufactured to the same engineering spec and nothing else has changed, a new part number can and more than likely will be generated. How a part is
packaged can cause part number changes! In a nutshell and without divulging any internal secrets, the 2001 head was a very limited production run. Small production runs equal increased cost. There was an anticipation by
engineering that a change might be required for the 2002 LS6 head to meet specific assembly line requirements, hence a new part number. The change had absolutely nothing to do with fit, form, or function of the LS6 cylinder head. It was also determined the '02 head would be used for the '03 models and that the new part number would also replace the 2001 service replacement part number when that stock was depleted. Therefore a lot more production and a lot less cost. For all practical purposes the bare cylinder heads are
identical.
The LS6 CNC cylinder heads fall under the GM Racing category. These part numbers can have radically different production changes in the finished product to enhance performance, without experiencing any part number changes. They are not intended to be service replacement parts for your car, in fact the sole purpose of parts that are produced by GM Racing is to win races. GM Racing has its own dedicated engineers for parts development and these parts are continuously being updated and improved to meet the demands
of racing. Therefore the block that you ordered two years ago may not be exactly the same the one you purchased today, even though it has the same
part number.
GM Racing changed the part number for the CNC LS6 heads this week, the new number is 88958622. If you purchased a set of 12480176 heads last year, then you received the 2001 LS6 assemblies with the 2001 GM CNC racing program. If you purchased a set of 12480176 heads this year (as long as it was not some dealer's old stock that had been sitting on the shelf for 9-months), you would have received a set 2002 LS6 assembled heads and the 2002 GM CNC porting. The part number change was made to avoid the internal problems of providing the correct parts for race teams with CNC ported heads, i.e.; do we need the '01 valves and valve springs or do we need the '02 springs and valves for repair and maintenance.
Besides the fact that the '01 and '02 heads have different valves and valve springs, the CNC porting was also changed for the '02 head. The sole intent of the CNC LS6 head from GM Racing is to support Corvettes competing in SCCA. I believe they are currently being used in the American LeMans series class known as Grand Am Cup. I have listed below the flow figures for the '02 CNC LS6 cylinder heads as tested on a SF1020 at 28" H2O on a 4.030" bore plate.
Lift Int Exh
.100 65 58
.200 138 113
.300 214 157
.400 261 191
.500 292 210
.525 295 212
.550 285 214
.600 282 218
One of the key things to remember about this particular head is that this CNC port was developed for a particular camshaft, hence the intake peaking in the 0.525" area. It was designed to provide maximum flow under the entire
lift curve! Air flow is a dynamic process occurring over a timed event. When comparing heads we look at the entire flow thru the cam profile. Also you should note these numbers are with the stock diameter valves. We have flowed
heads in back-to-back comparisons with larger intake valves that will not flow any more air than these and in some cases less. Port design, velocity past the valve, and flow quality are all very important features when evaluating cylinder head flow. Let's face it, GM has a bigger bank account to R&D head flow than all of us put together. They have done their homework on this head. Problem? These heads are very limited production and they are very hard to get. We are pushing them to increase their production. And yes
this CNC program is proprietary to GM Racing, so no you can not buy the same CNC port and valve job from anyone else.
We know for a fact from own testing that the light weight valves have a huge impact on performance. I think people tend to under rate the value of the '02 valves. This is kind of like getting titanium valves for the price of production stock valves, it is a real bargain.
The heads are milled 0.055", this brings the combustion chamber down to approximately 60.7cc's. This causes several concerns for installation, the least of which could be your compression ratio increase. One, you do need to
check the piston to valve clearance to verify that you have enough. We recommend a minimum of 0.080" on the intake and 0.100" on the exhaust. These are minimum numbers!
Next this means that it is absolutely necessary to check the pushrod length. I have read about some of your members wanting to upgrade their
lifters for high performance applications and/or having problems with lifters. We have found that a lot of lifter problems are the result of the
incorrect pushrod length, most of the time it is too long. The GM lifters are very good, especially with the '02 light weight valves and the correct pushrod length. The GM lifters are capable of supporting 7400rpm's on aggressive cam profiles. Obviously these heads will require a shorter pushrod if nothing else has changed except for the cylinder heads. Depending upon your camshaft and what base circle it has, you could need anywhere from a 7.200" to a 7.350" pushrod length(in most applications). We keep pushrods from 7.000" to 9.250" in 0.050" increments, FYI. Last, you must verify the
mounting of the intake to the heads. If you will notice, there are two brass inserts that are used as alignment dowels on the intake that are located at the passenger's side front corner (#2 intake port) and one at the driver's side rear (#7). With milled cylinder heads, these dowels can prevent the intake from fully seating against the intake gasket and causing a vacuum leak. These alignment dowels can easily be removed from the intake, at which point we will machine 0.050" off of the length then re-install the dowels
into the intake manifold. Make sure you check this!
Just FYI, we have had one customer report to us that by just changing the cylinder heads on his '02 ZO6 to the CNC version he picked-up 28 rwhp. He did this in a one-day session! Baselined the car, backed it off and changed the heads and pushrods, and back on!
Hope this answers most of the questions concerning the CNC ported heads. They are steal at $1970.00 per pair, but get in line. We have a waiting list now!
Nicky Fowler
SDPC
First, several questions have been asked about the price difference and why there are two different part numbers for the 2001 and 2002 bare LS6 cylinder heads. One of the most important facts to know about GM part numbers is that
there are about four basic distinct styles of part numbers within the GM hierarchy(internal, industrial, service replacement, and racing), only two of these have any real concern to the typical consumer. One being service replacement part numbers, such as the 2001 and 2002 LS6 cylinder heads.
These parts have a very strict set of guidelines, as in zero tolerance from the engineering print and specification. Something as simple as tapping one threaded hole an additional 0.100" deeper will require a complete new set of prints, validation testing, and a new part number in the GM system. If a change is made in suppliers, even though the part is still being manufactured to the same engineering spec and nothing else has changed, a new part number can and more than likely will be generated. How a part is
packaged can cause part number changes! In a nutshell and without divulging any internal secrets, the 2001 head was a very limited production run. Small production runs equal increased cost. There was an anticipation by
engineering that a change might be required for the 2002 LS6 head to meet specific assembly line requirements, hence a new part number. The change had absolutely nothing to do with fit, form, or function of the LS6 cylinder head. It was also determined the '02 head would be used for the '03 models and that the new part number would also replace the 2001 service replacement part number when that stock was depleted. Therefore a lot more production and a lot less cost. For all practical purposes the bare cylinder heads are
identical.
The LS6 CNC cylinder heads fall under the GM Racing category. These part numbers can have radically different production changes in the finished product to enhance performance, without experiencing any part number changes. They are not intended to be service replacement parts for your car, in fact the sole purpose of parts that are produced by GM Racing is to win races. GM Racing has its own dedicated engineers for parts development and these parts are continuously being updated and improved to meet the demands
of racing. Therefore the block that you ordered two years ago may not be exactly the same the one you purchased today, even though it has the same
part number.
GM Racing changed the part number for the CNC LS6 heads this week, the new number is 88958622. If you purchased a set of 12480176 heads last year, then you received the 2001 LS6 assemblies with the 2001 GM CNC racing program. If you purchased a set of 12480176 heads this year (as long as it was not some dealer's old stock that had been sitting on the shelf for 9-months), you would have received a set 2002 LS6 assembled heads and the 2002 GM CNC porting. The part number change was made to avoid the internal problems of providing the correct parts for race teams with CNC ported heads, i.e.; do we need the '01 valves and valve springs or do we need the '02 springs and valves for repair and maintenance.
Besides the fact that the '01 and '02 heads have different valves and valve springs, the CNC porting was also changed for the '02 head. The sole intent of the CNC LS6 head from GM Racing is to support Corvettes competing in SCCA. I believe they are currently being used in the American LeMans series class known as Grand Am Cup. I have listed below the flow figures for the '02 CNC LS6 cylinder heads as tested on a SF1020 at 28" H2O on a 4.030" bore plate.
Lift Int Exh
.100 65 58
.200 138 113
.300 214 157
.400 261 191
.500 292 210
.525 295 212
.550 285 214
.600 282 218
One of the key things to remember about this particular head is that this CNC port was developed for a particular camshaft, hence the intake peaking in the 0.525" area. It was designed to provide maximum flow under the entire
lift curve! Air flow is a dynamic process occurring over a timed event. When comparing heads we look at the entire flow thru the cam profile. Also you should note these numbers are with the stock diameter valves. We have flowed
heads in back-to-back comparisons with larger intake valves that will not flow any more air than these and in some cases less. Port design, velocity past the valve, and flow quality are all very important features when evaluating cylinder head flow. Let's face it, GM has a bigger bank account to R&D head flow than all of us put together. They have done their homework on this head. Problem? These heads are very limited production and they are very hard to get. We are pushing them to increase their production. And yes
this CNC program is proprietary to GM Racing, so no you can not buy the same CNC port and valve job from anyone else.
We know for a fact from own testing that the light weight valves have a huge impact on performance. I think people tend to under rate the value of the '02 valves. This is kind of like getting titanium valves for the price of production stock valves, it is a real bargain.
The heads are milled 0.055", this brings the combustion chamber down to approximately 60.7cc's. This causes several concerns for installation, the least of which could be your compression ratio increase. One, you do need to
check the piston to valve clearance to verify that you have enough. We recommend a minimum of 0.080" on the intake and 0.100" on the exhaust. These are minimum numbers!
Next this means that it is absolutely necessary to check the pushrod length. I have read about some of your members wanting to upgrade their
lifters for high performance applications and/or having problems with lifters. We have found that a lot of lifter problems are the result of the
incorrect pushrod length, most of the time it is too long. The GM lifters are very good, especially with the '02 light weight valves and the correct pushrod length. The GM lifters are capable of supporting 7400rpm's on aggressive cam profiles. Obviously these heads will require a shorter pushrod if nothing else has changed except for the cylinder heads. Depending upon your camshaft and what base circle it has, you could need anywhere from a 7.200" to a 7.350" pushrod length(in most applications). We keep pushrods from 7.000" to 9.250" in 0.050" increments, FYI. Last, you must verify the
mounting of the intake to the heads. If you will notice, there are two brass inserts that are used as alignment dowels on the intake that are located at the passenger's side front corner (#2 intake port) and one at the driver's side rear (#7). With milled cylinder heads, these dowels can prevent the intake from fully seating against the intake gasket and causing a vacuum leak. These alignment dowels can easily be removed from the intake, at which point we will machine 0.050" off of the length then re-install the dowels
into the intake manifold. Make sure you check this!
Just FYI, we have had one customer report to us that by just changing the cylinder heads on his '02 ZO6 to the CNC version he picked-up 28 rwhp. He did this in a one-day session! Baselined the car, backed it off and changed the heads and pushrods, and back on!
Hope this answers most of the questions concerning the CNC ported heads. They are steal at $1970.00 per pair, but get in line. We have a waiting list now!
Nicky Fowler
SDPC
07-12-2002 | 11:25 AM
#3
Re: 2002 GM CNC Ported Z06/LS6 Heads (INFO) AWESOME INFO!!!! THANK YOU SO MUCH!
so when is someone going to get a set of these to test with large duration cams? is there a cam that is designed with these heads?
so when is someone going to get a set of these to test with large duration cams? is there a cam that is designed with these heads?
07-12-2002 | 01:18 PM
#4
Re: 2002 GM CNC Ported Z06/LS6 Heads (INFO) Thanks for posting the info PSJ.
These heads look like a nice match for a hotcam or other lower lift grinds.
Any ideas where the 60.7cc chamber would put compression?
These heads look like a nice match for a hotcam or other lower lift grinds.
Any ideas where the 60.7cc chamber would put compression?
07-12-2002 | 04:43 PM
#5
Thread Starter
Joined: Nov 2001
Posts: 44,817
Likes: 1,244
From: Chicago, IL
Re: 2002 GM CNC Ported Z06/LS6 Heads (INFO) Oh and Ryan, LPE is the porter for the heads, but they CANNOT sell them to the public...
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Yes, the heads are machined at LPE. Actually that says a lot about the
quality of work that is done at LPE. It is incredibly difficult to become a
supplier to GM for any product.
But the problem is when we decide to announce to the world that LPE machines
the heads for GM, everyone wants to call LPE and try to buy the heads at a
better price or the proverbial, "I can't get any from my dealer and can ya
help out of a jam". LPE spends all of their time explaining why they can not
sell the GM heads and not enough time selling their own product and/or
developing new products for all of us to use on our hot rods. It is a
Catch-22.
It is not a secret that LPE machines the heads for GM. The serial number on
each head has the LPE stamping and each head has an LPE tag attached that
indicates - date of machining, valve size, CC of combustion chamber, guide
clearance, seat run-out, spring pressures, and coil bind.
If you want to see one these tags, then you will have to buy the heads from
a GM dealer!
Nicky Fowler
Scoggin-Dickey Parts Center
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Yes, the heads are machined at LPE. Actually that says a lot about the
quality of work that is done at LPE. It is incredibly difficult to become a
supplier to GM for any product.
But the problem is when we decide to announce to the world that LPE machines
the heads for GM, everyone wants to call LPE and try to buy the heads at a
better price or the proverbial, "I can't get any from my dealer and can ya
help out of a jam". LPE spends all of their time explaining why they can not
sell the GM heads and not enough time selling their own product and/or
developing new products for all of us to use on our hot rods. It is a
Catch-22.
It is not a secret that LPE machines the heads for GM. The serial number on
each head has the LPE stamping and each head has an LPE tag attached that
indicates - date of machining, valve size, CC of combustion chamber, guide
clearance, seat run-out, spring pressures, and coil bind.
If you want to see one these tags, then you will have to buy the heads from
a GM dealer!
Nicky Fowler
Scoggin-Dickey Parts Center
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">
07-12-2002 | 06:22 PM
#6
Re: 2002 GM CNC Ported Z06/LS6 Heads (INFO) PSJ You are the Man!
<img border="0" alt="[hail]" title="" src="graemlins/gr_hail.gif" /> <img border="0" alt="[hail]" title="" src="graemlins/gr_hail.gif" /> <img border="0" alt="[hail]" title="" src="graemlins/gr_hail.gif" /> <img border="0" alt="[hail]" title="" src="graemlins/gr_hail.gif" /> <img border="0" alt="[hail]" title="" src="graemlins/gr_hail.gif" />
This sounds wonderful but someone spell this out for a dummy like me:
What cams are a good match for these heads?
02 LS6 cam?
B1, T1? Hammer C1 or C2?
TR 220?
What compression do you end up with? at 60cc chambers? 11 to 1?
What length push rods would I need with a B1 cam or a TR 220?
I was thinking these could be a killer set up for a daily driver with a mild to medium cam with reasonable lift.
<small>[ July 12, 2002, 06:25 PM: Message edited by: 99 Black Bird T/A ]</small>
<img border="0" alt="[hail]" title="" src="graemlins/gr_hail.gif" /> <img border="0" alt="[hail]" title="" src="graemlins/gr_hail.gif" /> <img border="0" alt="[hail]" title="" src="graemlins/gr_hail.gif" /> <img border="0" alt="[hail]" title="" src="graemlins/gr_hail.gif" /> <img border="0" alt="[hail]" title="" src="graemlins/gr_hail.gif" />
This sounds wonderful but someone spell this out for a dummy like me:
What cams are a good match for these heads?
02 LS6 cam?
B1, T1? Hammer C1 or C2?
TR 220?
What compression do you end up with? at 60cc chambers? 11 to 1?
What length push rods would I need with a B1 cam or a TR 220?
I was thinking these could be a killer set up for a daily driver with a mild to medium cam with reasonable lift.
<small>[ July 12, 2002, 06:25 PM: Message edited by: 99 Black Bird T/A ]</small>
07-12-2002 | 07:11 PM
#7
Re: 2002 GM CNC Ported Z06/LS6 Heads (INFO) I think the heads are probably designed for two different cams. For the mild-medium set-up you have the hot cam. For a nice set-up that will produce more power than the hotcam, you have the ASA cam. If they still have these heads next year in january or so you can see the results of these heads and an asa cam on my car. The ASA cam is being put in within the next 2 weeks, and the heads will be on at the turn of the year. PSJ, whats the difference between these and the ASA heads? Whcih would be better for the cam? I've been unable to find any info on the ASA heads, can you provide the same info? Thanks!!
Jason
Jason
Trending Topics
07-14-2002 | 11:32 AM
#9
Re: 2002 GM CNC Ported Z06/LS6 Heads (INFO) Can we get some R&R results on how different cams react with this head? What cam owuld be cooonsidered the best to produce the most power. Thanks.
07-14-2002 | 06:07 PM
#11
Re: 2002 GM CNC Ported Z06/LS6 Heads (INFO) </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 98SS#2018:
<strong>IMHO the ASA cam would produce the most power... 226/236 .525/.525 110lsa... The max lift is at max flow, just my thoughts...
Jason</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">If you rev it extremely high it will produce the most power. For a street car I would go with the '02 LS6 cam, you have the springs and valves to make it work and it would be a wonderfull piece to use with these heads. Remember when you increase the flow you do not have to increase the duration as much to get better power levels.
Bret
<strong>IMHO the ASA cam would produce the most power... 226/236 .525/.525 110lsa... The max lift is at max flow, just my thoughts...
Jason</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">If you rev it extremely high it will produce the most power. For a street car I would go with the '02 LS6 cam, you have the springs and valves to make it work and it would be a wonderfull piece to use with these heads. Remember when you increase the flow you do not have to increase the duration as much to get better power levels.
Bret
07-14-2002 | 11:58 PM
#13
Re: 2002 GM CNC Ported Z06/LS6 Heads (INFO) So would the TEA 5.3L stage II ported heads. They flow a little better and they are about the same price.
Both the LS6 cams would be a great cam with these heads.
Bret
Both the LS6 cams would be a great cam with these heads.
Bret
07-16-2002 | 03:30 PM
#14
On The Tree
Joined: Mar 2002
Posts: 172
Likes: 0
From: Plano, TX USA
Re: 2002 GM CNC Ported Z06/LS6 Heads (INFO) Are you saying that there are two 2002 LS6 Head Versions?
Like a CNC 2002 LS6 Head and also a normal everday 2002 Z06 LS6 Head? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
Like a CNC 2002 LS6 Head and also a normal everday 2002 Z06 LS6 Head? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
07-16-2002 | 03:36 PM
#15
Re: 2002 GM CNC Ported Z06/LS6 Heads (INFO) the CNC LS6 head is a factory head that has been treated to a CNC program to allow for better flow. instead of hand porting them, they are machine ported. CNC=computer numerically controled.
07-18-2002 | 07:50 PM
#19
Re: 2002 GM CNC Ported Z06/LS6 Heads (INFO) I have a question. I noticed the 4.030" bore plate when the heads were flowed and I was wondering if this means that the head is designed for this size piston or can these heads be bolted on to a stock 5.7 setup? Also with the peak flow being at .525 what would the most amount of lift over that would you go. I understand that this was probably designed for the ASA cam or something of that nature, but would something like the TR224 work well with these heads? Thanks for any answers.
Chris
Chris
