LS6 CNC heads flowed @ MTI - Interesting info
11-13-2002, 11:45 PM
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LS6 CNC heads flowed @ MTI - Interesting info My buddy John bought a set of CNC LS6 heads from SDPC. Before he bolted them on he decided to take them to MTI to have them flowed. MTI was interested since I do not think they had seen a set up to this point to compare to their heads.
A valve was popped loose and the intake and exhaust ports were flowed. Several interesting fact came to light during this test.
First, if there was ever and question that these heads were done for GM by LPE, there isn't now. They have a tag from Lingenfelter, and they have a serial number LPExxxx stamped into the head. So, I would say they are definitely LPE stuff.
The next interesting thing is that the head is welded up. What I mean by that is that they go high into the top of the runner and actually break through the top of the port. They build it up with a bit of weld metal to close the hole. I suspect this is done before they are ported. There are several people out there who do this. MTI however is not one of them. According to their head porter instead of going up in the port, he goes into the floor. I found this unusual as most people try to stay off the floor of a port and work to raise the runner. But, this is what they do, and it seems to work for them.
I know there has been concern over the heads being milled .055 don't let this worry you if you are considering them. The chambers are reshaped during the CNC process and metal around the valve has been removed. By milling the head you get to about a 60cc combustion chamber. According to MTI that is exactly what they shoot for on their heads 60-61cc.
In looking at the intake flow numbers they appear to correlate with some early numbers posted by SDPC. The post with pictures of the heads. Well, let me say, they matched on the intake dead on. On the exhaust they were about 7CFM lower on Jason's bench vs the SDPC numbers.
They were nice enough to bring up the graph of the heads and overlay some of their own heads for comparison. The first graph they brough up was the graph for the heads on Jayson's own car. These are the "best" heads they know how to do. I think peak flow numbers were around +340 cfm. They absolutely destroyed the CNC heads when comparing the two. Better across the board by a wide margin. I think Jayson's heads are Stage III Ls6 heads on his 422 but I am not 100% certain.
John asked to see a graph of the LS6CNC vs a "typical" MTI head. So, they scrolled down and pulled up some other head. I do not know whose heads these were. I believe these were some Stage II Ls1 heads, but I don't know for sure. In looking at the graphs layed over one another the thing that was clear that the CNC heads outflowed the MTI heads until about .500 at that point the graphs converged together. at .550 the MTI heads were pulling away, and at .600 the CNC heads went turbulent and dropped like a stone. As a side note, the MTI heads never went turbulent and would continue to flow until .700. The LS6 CNC head flowed until .590. Once you opened the port to .600 it got noisy and really turbulent (it was obvious when you were listening). So these heads should not be used with more than .590 lift on the intake period. I think the MTI heads were making 318 @ either .500 or .550 I can't remember which, and I only have the numbers for the LS6 in front of me.
Here are the numbers off Jayson's bench.
Intake
.100 - 67
.200 - 142
.300 - 210
.400 - 254
.500 - 290
.550 - 304
.600 - 286
Exhaust
.100 - 50
.200 - 104
.300 - 150
.400 - 185
.500 - 203
.550 - 210
.600 - 212
One of the other things that was noted is that the CNC heads exhaust flowed about 70% more or less across the board. MTI heads flowed MUCH better on the exhaust side. They were consistently ahead by about 50 CFM in the higher lifts if memory serves me correctly.
In discussing this with John we began to come up with several points that we began to discuss. If you look at the ASA and the World Cup cams you will notice they are MUCH bigger on the exhaust side. If you look at the "tuner" cams they are either even, and some tuner cams are working on "reverse split". I don't know if this is due to the fact that the percentages on the exhaust are much closer than on the CNC heads. Also, there was some question as to whether the exhaust ports were too efficent, and the cams were being used to make up for insuficient intake flow vs exhaust flow.
Overall I think it was an interesting test. Jayson and his head porting folks seemed to feel that for the price these heads were certainly a pretty good bargain. One of the other things the porter noted that he felt that smoothing out the CNC imperfections left by the tooling could be worth 6-8 CFM on the intake alone.
Anyhow, props to Jayson and the crew @ MTI for their help...
If you wish to see the flow numbers MTI has them saved under the filename Lingenfelter. So, no those aren't heads hand ported by Lingenfelter, they are just plain old CNC heads.
<small>[ November 14, 2002, 12:00 AM: Message edited by: J-Rod ]</small>
A valve was popped loose and the intake and exhaust ports were flowed. Several interesting fact came to light during this test.
First, if there was ever and question that these heads were done for GM by LPE, there isn't now. They have a tag from Lingenfelter, and they have a serial number LPExxxx stamped into the head. So, I would say they are definitely LPE stuff.
The next interesting thing is that the head is welded up. What I mean by that is that they go high into the top of the runner and actually break through the top of the port. They build it up with a bit of weld metal to close the hole. I suspect this is done before they are ported. There are several people out there who do this. MTI however is not one of them. According to their head porter instead of going up in the port, he goes into the floor. I found this unusual as most people try to stay off the floor of a port and work to raise the runner. But, this is what they do, and it seems to work for them.
I know there has been concern over the heads being milled .055 don't let this worry you if you are considering them. The chambers are reshaped during the CNC process and metal around the valve has been removed. By milling the head you get to about a 60cc combustion chamber. According to MTI that is exactly what they shoot for on their heads 60-61cc.
In looking at the intake flow numbers they appear to correlate with some early numbers posted by SDPC. The post with pictures of the heads. Well, let me say, they matched on the intake dead on. On the exhaust they were about 7CFM lower on Jason's bench vs the SDPC numbers.
They were nice enough to bring up the graph of the heads and overlay some of their own heads for comparison. The first graph they brough up was the graph for the heads on Jayson's own car. These are the "best" heads they know how to do. I think peak flow numbers were around +340 cfm. They absolutely destroyed the CNC heads when comparing the two. Better across the board by a wide margin. I think Jayson's heads are Stage III Ls6 heads on his 422 but I am not 100% certain.
John asked to see a graph of the LS6CNC vs a "typical" MTI head. So, they scrolled down and pulled up some other head. I do not know whose heads these were. I believe these were some Stage II Ls1 heads, but I don't know for sure. In looking at the graphs layed over one another the thing that was clear that the CNC heads outflowed the MTI heads until about .500 at that point the graphs converged together. at .550 the MTI heads were pulling away, and at .600 the CNC heads went turbulent and dropped like a stone. As a side note, the MTI heads never went turbulent and would continue to flow until .700. The LS6 CNC head flowed until .590. Once you opened the port to .600 it got noisy and really turbulent (it was obvious when you were listening). So these heads should not be used with more than .590 lift on the intake period. I think the MTI heads were making 318 @ either .500 or .550 I can't remember which, and I only have the numbers for the LS6 in front of me.
Here are the numbers off Jayson's bench.
Intake
.100 - 67
.200 - 142
.300 - 210
.400 - 254
.500 - 290
.550 - 304
.600 - 286
Exhaust
.100 - 50
.200 - 104
.300 - 150
.400 - 185
.500 - 203
.550 - 210
.600 - 212
One of the other things that was noted is that the CNC heads exhaust flowed about 70% more or less across the board. MTI heads flowed MUCH better on the exhaust side. They were consistently ahead by about 50 CFM in the higher lifts if memory serves me correctly.
In discussing this with John we began to come up with several points that we began to discuss. If you look at the ASA and the World Cup cams you will notice they are MUCH bigger on the exhaust side. If you look at the "tuner" cams they are either even, and some tuner cams are working on "reverse split". I don't know if this is due to the fact that the percentages on the exhaust are much closer than on the CNC heads. Also, there was some question as to whether the exhaust ports were too efficent, and the cams were being used to make up for insuficient intake flow vs exhaust flow.
Overall I think it was an interesting test. Jayson and his head porting folks seemed to feel that for the price these heads were certainly a pretty good bargain. One of the other things the porter noted that he felt that smoothing out the CNC imperfections left by the tooling could be worth 6-8 CFM on the intake alone.
Anyhow, props to Jayson and the crew @ MTI for their help...
If you wish to see the flow numbers MTI has them saved under the filename Lingenfelter. So, no those aren't heads hand ported by Lingenfelter, they are just plain old CNC heads.
<small>[ November 14, 2002, 12:00 AM: Message edited by: J-Rod ]</small>
11-13-2002, 11:55 PM
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Re: LS6 CNC heads flowed @ MTI - Interesting info Not bad for stock valves. Well not completely stock, the intake valves are backcut. I've often wondered how much bigger valves would affect the LS6 CNC'd heads.
11-14-2002, 12:02 AM
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Thread Starter
Re: LS6 CNC heads flowed @ MTI - Interesting info SDPC said they tried bigger valves and it made no difference on these heads. The port was designed around a stock sized valve. The 2001 heads had higher peak numbers and would flow well past .600 the 2002 heads were revised to work better with the stock valves and to pick up mid-lift over peak numbers.
11-14-2002, 12:03 AM
#5
Re: LS6 CNC heads flowed @ MTI - Interesting info Excellent info!
Would it be possible to get flow info with the LS6 intake attached? This would give an even better idea of how well the heads really flow.
Reason I asked is my heads dropped ~50cfm with the LS6 intake in place vs no intake.
Would it be possible to get flow info with the LS6 intake attached? This would give an even better idea of how well the heads really flow.
Reason I asked is my heads dropped ~50cfm with the LS6 intake in place vs no intake.
11-14-2002, 11:22 AM
#6
6600 rpm clutch dump of death Administrator
Thread Starter
Re: LS6 CNC heads flowed @ MTI - Interesting info I think everyone accepts that there is a signifcant drop in flow once the intake is in place. I believe there was a flow test done with the intake in place on some really good flowing heads. I think the went from 340 down to around 300-315 with the intake in place. The intake is a restriction no matter how you slice it. A lot of your gains that you pick up from head flow are negated by the intake. But in all motors, the intake ususally does drop flow to some degree. Good heads simply move the restriction back to the intake. If you fix the intake, then you have to fix the Throttle body, and so forth...
It would be nice if we could fix it all.
It would be nice if we could fix it all.
11-14-2002, 11:55 AM
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Re: LS6 CNC heads flowed @ MTI - Interesting info Very informitive post, J-Rod. A couple of things to keep in mind, that is a program that we use on the GM heads. When GM approached us to do the heads for them, they requested certain flow numbers at certain lifts, and that is what they are. GM also requires us to flow the heads with an intake attached, and with a 6" exhaust tube in place. We have our own program that we use on our in-house packages and out-the-door customers. Also, like you said, that is with no hand polishing or bigger valves. Just wanted to fill in some of the blank spaces that nobody in the 'outside world' would know!! <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
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11-14-2002, 02:13 PM
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6600 rpm clutch dump of death Administrator
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Re: LS6 CNC heads flowed @ MTI - Interesting info Absolutely Josh. You bring up two good points. GM and the SCCA had certain numbers at a certain lift they wanted to see. Your heads met those criteria, and did so with the stock valves. If not for those restrictions, these heads would most likely be quite a bit different in design. I do think it is important for folks to understand that these were purpose built heads.
So, people need to understand that these aren't the same as the heads that you sell out the door @ LPE. This is a GM specific CNC profile.
I would suspect that your "standard" head program is probably quite a bit different than these. I know in your response over on the Corvetteforum about these results you stated that there were some improvements that could be made on these heads.
For anyone considering a set of these heads what are some reasonable upgrades that could be done to the heads?
As I said I suspect a set of these heads differ from the heads you do for your customers. What upgrades can you do to these heads @ LPE? How much would that cost? Would it be more cost effective to simply buy heads outright from LPE if the numbers on the CNC heads aren't up to your liking?
One other qurestion. Do you have some flow numbers for your "customer" heads that go out the door @ LPE?
Thanks for your help, and for your posts.
<small>[ November 14, 2002, 02:14 PM: Message edited by: J-Rod ]</small>
So, people need to understand that these aren't the same as the heads that you sell out the door @ LPE. This is a GM specific CNC profile.
I would suspect that your "standard" head program is probably quite a bit different than these. I know in your response over on the Corvetteforum about these results you stated that there were some improvements that could be made on these heads.
For anyone considering a set of these heads what are some reasonable upgrades that could be done to the heads?
As I said I suspect a set of these heads differ from the heads you do for your customers. What upgrades can you do to these heads @ LPE? How much would that cost? Would it be more cost effective to simply buy heads outright from LPE if the numbers on the CNC heads aren't up to your liking?
One other qurestion. Do you have some flow numbers for your "customer" heads that go out the door @ LPE?
Thanks for your help, and for your posts.
<small>[ November 14, 2002, 02:14 PM: Message edited by: J-Rod ]</small>
11-14-2002, 02:36 PM
#10
Re: LS6 CNC heads flowed @ MTI - Interesting info The reason why the heads are what they are is due to the racing- ASA and World Challenge. They are not allowed to go BIG on valves, and we all know that the ASA cam (USED to be the spec cam for the World Challenge cars) has a max lift of 525. with those perameters outlined, LPE then went to work with in those perameters and did the best they could.
The ASA cars typically put down 420-430 @ the wheels but keep in mind the clutches they use are about 5-7" in diameter, and much lighter than what we use on the street, + a much more efficient drivetrain. <img border="0" title="" alt="[Cool]" src="gr_images/icons/cool.gif" />
Not a bad head IMO <img border="0" alt="[Burnout]" title="" src="graemlins/burnout.gif" />
The ASA cars typically put down 420-430 @ the wheels but keep in mind the clutches they use are about 5-7" in diameter, and much lighter than what we use on the street, + a much more efficient drivetrain. <img border="0" title="" alt="[Cool]" src="gr_images/icons/cool.gif" />
Not a bad head IMO <img border="0" alt="[Burnout]" title="" src="graemlins/burnout.gif" />
11-14-2002, 06:16 PM
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Re: LS6 CNC heads flowed @ MTI - Interesting info just curious. the plenum size on the ls6 intake is larger. are the ports also larger (wider) is that why they flow better?
11-14-2002, 06:39 PM
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Re: LS6 CNC heads flowed @ MTI - Interesting info IMO these heads are a great buy, $1800 out the door. No core charge (so you can sell your stock for $300 and have $1500 into the heads) You have a LS6 head that certainly could be upgraded with additional porting, in the future.
I'm sure that the majority are using a cam with a lift under the .590. So this would be a great buy.
I would like to know what cams have been matched to these heads?
I do know someone who is running 10's on motor, 346, with these heads. Not sure what the cam is. Great info on the heads, thanks.
I'm sure that the majority are using a cam with a lift under the .590. So this would be a great buy.
I would like to know what cams have been matched to these heads?
I do know someone who is running 10's on motor, 346, with these heads. Not sure what the cam is. Great info on the heads, thanks.
11-14-2002, 06:46 PM
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Re: LS6 CNC heads flowed @ MTI - Interesting info Thanks for all of the info <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
MTI <img border="0" alt="[Burnout]" title="" src="graemlins/burnout.gif" />
MTI <img border="0" alt="[Burnout]" title="" src="graemlins/burnout.gif" />
11-14-2002, 07:32 PM
#16
Re: LS6 CNC heads flowed @ MTI - Interesting 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 Josh @ LPE:
<strong>GM also requires us to flow the heads with an intake attached, and with a 6" exhaust tube in place.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">There has to a reason GM requires that. Can you give us any additional insight?
Thanks
<strong>GM also requires us to flow the heads with an intake attached, and with a 6" exhaust tube in place.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">There has to a reason GM requires that. Can you give us any additional insight?
Thanks
11-15-2002, 12:33 AM
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Re: LS6 CNC heads flowed @ MTI - Interesting info "It would be nice if we could fix it all. "
thats what Hillborn injection was designed for ;D
thats what Hillborn injection was designed for ;D
11-15-2002, 07:39 AM
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Re: LS6 CNC heads flowed @ MTI - Interesting 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 J-Rod:
<strong>Absolutely Josh. You bring up two good points. GM and the SCCA had certain numbers at a certain lift they wanted to see. Your heads met those criteria, and did so with the stock valves. If not for those restrictions, these heads would most likely be quite a bit different in design. I do think it is important for folks to understand that these were purpose built heads.
So, people need to understand that these aren't the same as the heads that you sell out the door @ LPE. This is a GM specific CNC profile.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">That is correct.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">For anyone considering a set of these heads what are some reasonable upgrades that could be done to the heads?
As I said I suspect a set of these heads differ from the heads you do for your customers. What upgrades can you do to these heads @ LPE? How much would that cost? Would it be more cost effective to simply buy heads outright from LPE if the numbers on the CNC heads aren't up to your liking? [/QB]</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">We could go and put bigger valves in the GM heads and get a reasonable gain in flow, but that may get you to our base (Stage I) LS6 program. Here are the #'s for our Stage I heads:
.200 153 120
.300 228 171
.400 276 205
.450 288 213
.500 294 220
.550 307 224
.600 314 225
These heads sell for $2995 outright ($1595 if you have a set of good cores).
The GM LS6 heads, in my opinion, would be a good choce for a guy that is just looking for a little more power for the street. On the other hand, if a guy is racing the car and wants every last bit of power, then I think our bigger-valve, hand finished LS6 heads would be a good choice. I don't have any flow #'s for these at this time, but I will try to round them up today sometime.
<strong>Absolutely Josh. You bring up two good points. GM and the SCCA had certain numbers at a certain lift they wanted to see. Your heads met those criteria, and did so with the stock valves. If not for those restrictions, these heads would most likely be quite a bit different in design. I do think it is important for folks to understand that these were purpose built heads.
So, people need to understand that these aren't the same as the heads that you sell out the door @ LPE. This is a GM specific CNC profile.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">That is correct.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">For anyone considering a set of these heads what are some reasonable upgrades that could be done to the heads?
As I said I suspect a set of these heads differ from the heads you do for your customers. What upgrades can you do to these heads @ LPE? How much would that cost? Would it be more cost effective to simply buy heads outright from LPE if the numbers on the CNC heads aren't up to your liking? [/QB]</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">We could go and put bigger valves in the GM heads and get a reasonable gain in flow, but that may get you to our base (Stage I) LS6 program. Here are the #'s for our Stage I heads:
.200 153 120
.300 228 171
.400 276 205
.450 288 213
.500 294 220
.550 307 224
.600 314 225
These heads sell for $2995 outright ($1595 if you have a set of good cores).
The GM LS6 heads, in my opinion, would be a good choce for a guy that is just looking for a little more power for the street. On the other hand, if a guy is racing the car and wants every last bit of power, then I think our bigger-valve, hand finished LS6 heads would be a good choice. I don't have any flow #'s for these at this time, but I will try to round them up today sometime.
11-15-2002, 01:09 PM
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Re: LS6 CNC heads flowed @ MTI - Interesting info SDPC are offering these heads. You can select Manley or Compcams springs/retainers. <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />
11-16-2002, 12:08 AM
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Re: LS6 CNC heads flowed @ MTI - Interesting info Those GM LS6 heads do really look like a good buy. The bigest weakness I see here are those valve springs. Don't you think that most of us would need to rip those things out? Is there any way to order those heads with a spring set up that will survive aftermarket cams?