Newly Updated PRC LS7 CNC Heads Break 400CFM!!
07-03-2008, 08:17 PM
#61
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Once again, it's time to dispell old myth from current fact..... as this quote from David Reher of Reher-Morrison racing engines attests - "Textbooks would lead you to believe that an exhaust to intake flow ratio of 80 percent is ideal - yet a typical Pro Stock head has exhaust ports that flow less than 60 percent of the intake runners." He goes on the say "You can improve the exhaust flow tremendously with about 40 minutes of work with a hand grinder - but the supposed improvements will just about kill the engine's on-track performance. I know because I've been there." And you know what.... he's dead right. After over 100 dyno pulls with 3 different 400+ cube LS engines, I can say without a doubt that there is NOTHING wrong with the exhaust ports on these heads. Take the L92 headed 427 which we dynoed, then pulled the heads and changed the valve seat angles from 45 degrees to 55 degrees (significantly hurting the flow numbers across the board) and then re-installed them on the motor and pulled it again.... the results: ZERO change in power and torque EVERYWHERE. So much for exhaust flowbench numbers meaning anything. And then there's the 454 we built w/ L92 heads and an LS7 intake manifold that makes 706 HP and 631 tq on pump gas w/ a hydraulic roller cam. Tried 3 different exhaust valve size and shape combos, didn't make any difference either. The intake port on the other hand was a different story....when ported to flow 360 cfm, in a configuration identical to everyone elses L92 heads, the motor wouldn't make more than 640 HP. After deciding to forget the flow bench and make the port LOOK right (this included a little TIG welding in the port and chamber, btw), the port LOST flow on the bench but miraculously gained 45 HP. Another item of note, the single plane manifold we tried made the same torque and hp as the LS7.... so much for the plastic manifold not making any power. The real limit on the L92 head is the valve length limiting the roof height at the guide and it is this that causes them to quit making power..... NOT the manifold or the exhaust port. The LS7 head has a valve that's about .350" longer it is because of this that we can make even more power with them over the L92/LS3's.
07-03-2008, 10:52 PM
#63
Launching!
Once again, it's time to dispell old myth from current fact..... as this quote from David Reher of Reher-Morrison racing engines attests - "Textbooks would lead you to believe that an exhaust to intake flow ratio of 80 percent is ideal - yet a typical Pro Stock head has exhaust ports that flow less than 60 percent of the intake runners." He goes on the say "You can improve the exhaust flow tremendously with about 40 minutes of work with a hand grinder - but the supposed improvements will just about kill the engine's on-track performance. I know because I've been there." And you know what.... he's dead right. After over 100 dyno pulls with 3 different 400+ cube LS engines, I can say without a doubt that there is NOTHING wrong with the exhaust ports on these heads. Take the L92 headed 427 which we dynoed, then pulled the heads and changed the valve seat angles from 45 degrees to 55 degrees (significantly hurting the flow numbers across the board) and then re-installed them on the motor and pulled it again.... the results: ZERO change in power and torque EVERYWHERE. So much for exhaust flowbench numbers meaning anything. And then there's the 454 we built w/ L92 heads and an LS7 intake manifold that makes 706 HP and 631 tq on pump gas w/ a hydraulic roller cam. Tried 3 different exhaust valve size and shape combos, didn't make any difference either. The intake port on the other hand was a different story....when ported to flow 360 cfm, in a configuration identical to everyone elses L92 heads, the motor wouldn't make more than 640 HP. After deciding to forget the flow bench and make the port LOOK right (this included a little TIG welding in the port and chamber, btw), the port LOST flow on the bench but miraculously gained 45 HP. Another item of note, the single plane manifold we tried made the same torque and hp as the LS7.... so much for the plastic manifold not making any power. The real limit on the L92 head is the valve length limiting the roof height at the guide and it is this that causes them to quit making power..... NOT the manifold or the exhaust port. The LS7 head has a valve that's about .350" longer it is because of this that we can make even more power with them over the L92/LS3's.
Interesting data on the exhaust port tests. Given that the bulk of exhaust flow occurs at high pressure and velocity, it is perhaps not surprising that you got better results with steeper valve seat angles - exactly the opposite of what works at low pressure/velocity on the flow bench.
07-04-2008, 02:12 AM
#64
check this post out. https://ls1tech.com/forums/showthrea...193&highlight=
07-05-2008, 09:46 AM
#65
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Interesting data on the exhaust port tests. Given that the bulk of exhaust flow occurs at high pressure and velocity, it is perhaps not surprising that you got better results with steeper valve seat angles - exactly the opposite of what works at low pressure/velocity on the flow bench.
07-08-2008, 11:30 AM
#66
Guys all we ever ship is the smaller port heads. They move about 390 cfm & work really well. We've never seen less than 30rwhp from installing these in place of factory heads.
The bigger runner head will be dyno tested on a ls7 454 shortly. I'll let you guys know if it's worth the extra port size on the dyno.
The bigger runner head will be dyno tested on a ls7 454 shortly. I'll let you guys know if it's worth the extra port size on the dyno.
Thanks!
09-21-2008, 03:27 PM
#67
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Exhaust Flow I'm new into looking at the LS7 and other heads for LS engines but in general they all appear to have lower flow exhaust flow than would be optimal. Being a guy who has put together a few BBC engines, exhaust flow is the key to performance on this motor - suspect same is true of the new little brother. It would be nice if someone could match AFR's CNC 335 BBC head performance in the LS series - now you would be talking real power.
09-22-2008, 09:12 PM
#69
Launching!
I'm new into looking at the LS7 and other heads for LS engines but in general they all appear to have lower flow exhaust flow than would be optimal. Being a guy who has put together a few BBC engines, exhaust flow is the key to performance on this motor - suspect same is true of the new little brother. It would be nice if someone could match AFR's CNC 335 BBC head performance in the LS series - now you would be talking real power.
To another point, the LS7 head can never match the AFR 335 in combined intake and exhaust flow, for the simple reason that the AFR 335 is designed for a 4.5 bore, and the LS7 for a 4.125 bore. The AFR has a huge built-in advantage because the 4.5 bore allows for .375 more diameter to be allocated between intake and exhaust valve. Given that advantage, it's astonishing how close the LS7 head comes in maximum HP potential.
09-23-2008, 11:06 AM
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09-27-2008, 10:26 PM
#72
and still waiting........................................... .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. ........................ding time's up I guess I'll buy the tfs's. Waited on you guys since you announced them. Mabe if you'd even post up in your own post I would still buy them but since it's been a few days I'll have to buy somewhere else.
09-29-2008, 09:36 AM
#73
The 6 bolt head is not ready to be released yet. We'll post up everywhere when they are for sale.
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05-16-2010, 10:18 AM
#74
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Truth be told Guys I appreciate you going out of your way to move the original thread off-course. Here we are again doing the best we can to try to cloud & discredit the newest PRC cylinder head. I can't blame people for being negative about it, it's hands down the most powerful LS7 cylinder head available at this time!
We spend tons of time during the R&D stages of cylinder head development & testing. While you guys are reading magazines & getting "hardcore" information off the internet, we're dyno testing our cylinder heads on both chassis dynos & engine dynos.
In the future I will flow all the exhaust ports with a exhaust pipe to hype up the exhaust numbers so you guys can feel warm & fuzzy about it. The bottom line is a lot of time went into the development of both the intake & exhaust port on our PRC LS7 Cylinder Heads. I'm damn tired of people getting on the internet with absolutely no cylinder head knowledge, & attempting to discredit a really good product. You can argue all you want that big airflow from the LS7 cylinder head doesn't matter because the LS7 intake is a restricition, but I'll take the 30rwhp gains & 600rwhp LS7 power potential ANYDAY!!
The PRC cylinder heads are built with only 7cc's of additional material removed from the original ports. Your getting huge airflow gains with minimal changes in port volume! As a result you get throttle response that matches the stock heads with power potential that completely smashes the stock LS7 head.
The ports on our LS7 cylinder head were designed by one of the leading LS cylinder head guys in the country. These cylinder heads have pushed a pump gas 454lsx over 750fwhp & consistantly makes 30rwhp over a stock cylinder head. My personal z06 makes 605rwhp to the tire with our out of the box head & a ported LS7 intake. So I guess to answer your question, not every ported LS7 head only makes 15rwhp. You don't have to take my word for it, go search corvetteforum. We sell to tons of the vendors there & they constantly see 30+rwhp gains! I even had a phone call from a customer in Abu Dhabi UAE that made a additional 32rwhp after installing our cylinders heads.
I've personally never seen less than 30rwhp gains from our ls7 heads.
I guess I could sit here all day & discuss what magazines told you, but I've got a Pro Stock car to work on today! So in a effort to save time I've got a few results I found with the help of the trusty search button.
Here's my dyno sheet from my LS7 Z06
Here's the engine dyno results from stock LS7 heads to the PRC LS7 heads at a independent engine dyno shop!
http://www.texasquadperformance.com/lsx454.mpg
Testing was done with both cylinder heads using the same valves & set to 70cc chambers.
Dyno test with stock GM cnc ported LS7 cylinder heads:
Dyno test with Precision Race Components CNC Ported LS7 Cylinder Heads:
We spend tons of time during the R&D stages of cylinder head development & testing. While you guys are reading magazines & getting "hardcore" information off the internet, we're dyno testing our cylinder heads on both chassis dynos & engine dynos.
In the future I will flow all the exhaust ports with a exhaust pipe to hype up the exhaust numbers so you guys can feel warm & fuzzy about it. The bottom line is a lot of time went into the development of both the intake & exhaust port on our PRC LS7 Cylinder Heads. I'm damn tired of people getting on the internet with absolutely no cylinder head knowledge, & attempting to discredit a really good product. You can argue all you want that big airflow from the LS7 cylinder head doesn't matter because the LS7 intake is a restricition, but I'll take the 30rwhp gains & 600rwhp LS7 power potential ANYDAY!!
The PRC cylinder heads are built with only 7cc's of additional material removed from the original ports. Your getting huge airflow gains with minimal changes in port volume! As a result you get throttle response that matches the stock heads with power potential that completely smashes the stock LS7 head.
The ports on our LS7 cylinder head were designed by one of the leading LS cylinder head guys in the country. These cylinder heads have pushed a pump gas 454lsx over 750fwhp & consistantly makes 30rwhp over a stock cylinder head. My personal z06 makes 605rwhp to the tire with our out of the box head & a ported LS7 intake. So I guess to answer your question, not every ported LS7 head only makes 15rwhp. You don't have to take my word for it, go search corvetteforum. We sell to tons of the vendors there & they constantly see 30+rwhp gains! I even had a phone call from a customer in Abu Dhabi UAE that made a additional 32rwhp after installing our cylinders heads.
I've personally never seen less than 30rwhp gains from our ls7 heads.
I guess I could sit here all day & discuss what magazines told you, but I've got a Pro Stock car to work on today! So in a effort to save time I've got a few results I found with the help of the trusty search button.
Here's my dyno sheet from my LS7 Z06
Here's the engine dyno results from stock LS7 heads to the PRC LS7 heads at a independent engine dyno shop!
http://www.texasquadperformance.com/lsx454.mpg
Testing was done with both cylinder heads using the same valves & set to 70cc chambers.
Dyno test with stock GM cnc ported LS7 cylinder heads:
Dyno test with Precision Race Components CNC Ported LS7 Cylinder Heads:
Anyhow, i know of guy in AbuDhabi with your heads and yes he did get over 30RWHP on his C6Z. I also had a set on my car from Jason, it actually had my name on them, but unfortunately when i sent my motor to be rebuilt by someone in the US, i got back something different.
I have to be fair here, I felt the power and tq instantly. i didnt dyno the car, but if you take street performce and motor revs at mid and higher RPMs as an indication of power, then those heads were a welcomed addition to my motor. unfortunately they are no longer part of my motor.
BTW, the 30rwhp that guy got, was on a stock motor with add ons. No cam at that time.
Now for your 285cc, did you finalize your ports yet? Also, if we go with bigger springs, would there be a need to retain the Ti intake valves?
What can you do to the FAST intake to make it compliment the head?
05-16-2010, 10:29 AM
#75
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Different Intakes Jason
Can you elaborate on the results of the Carb and Beck's test on these heads?
That being said a better flowing intake could be a big positive, but it all depends on how you get to that point. We've tested carb intakes & sheet metal beck intakes on our cylinder heads with interesting results. The intake changes power output drastically & modifying the intake can change power output characteristics as drastically as a huge cam change! That being said if you could create a intake similar to the stock LS7 intake with better airflow you'd definately see a power gain. Unfortunately it wouldn't be anything near that 2.2hp per cfm figure the magazines taught you.
Can you elaborate on the results of the Carb and Beck's test on these heads?
That being said a better flowing intake could be a big positive, but it all depends on how you get to that point. We've tested carb intakes & sheet metal beck intakes on our cylinder heads with interesting results. The intake changes power output drastically & modifying the intake can change power output characteristics as drastically as a huge cam change! That being said if you could create a intake similar to the stock LS7 intake with better airflow you'd definately see a power gain. Unfortunately it wouldn't be anything near that 2.2hp per cfm figure the magazines taught you.
