LS6 CNC heads from GMPP
07-30-2002, 10:10 AM
#2
Re: LS6 CNC heads from GMPP Now that you mention it Ryan. I was looking at those very heads in my GM Parts book and I almost jumped on them.. Personally I think they would work well. I do not know the flow #'s, but I am sure they are better than stock. The LS6 heads flow better than LS1 heads by almost 30cfm from the factory. CNC'd they should be better.. I say try a set. It cant hurt.
07-30-2002, 10:40 AM
#3
LS1Tech Co-Founder
iTrader: (34)
Re: LS6 CNC heads from GMPP Here is the info from Nicky Fowler...
**************
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
Scoggin-Dickey Parts Center
**************
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
Scoggin-Dickey Parts Center
07-30-2002, 02:12 PM
#4
Re: LS6 CNC heads from GMPP That sounds like a deal. The midrange would be killer.. I should have gone with these heads a while ago.. These heads and the ASA cam would be killer on the street..
<small>[ July 30, 2002, 02:17 PM: Message edited by: VINCE ]</small>
<small>[ July 30, 2002, 02:17 PM: Message edited by: VINCE ]</small>
