Hi. Preparing for the DoD delete build. I ordered the GMPP CNC heads from JEGS but they are backordered, so I'm beginning to question my choice. I wanted to upgrade my intake valves, which would also require new seals, and the price of the CNC heads at $1200 just made sense to me. The factory LS3 heads from JEGS are only $700. What do you think? Am I wasting money on my build with the CNC heads? Some day I may want to stroke it or do something more so the cost of the CNC heads at $500 more seem to make sense. But my 6.0 may do better with the LS3 heads. In any event, I will sell my factory heads to recoup some of the money. For those that have the CNC heads, was it worth it performance wise? And since I am not replacing rods and rod bolts will I see enough "safe" rpms to benefit from the ported heads?
Factory LS3 heads vs. CNC heads
deb0650
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Not that I disagree with you because obviously your much more knowledgable in this department than me or even most people, but how can LS3 heads out power cathedral heads with a good intake?
When I read Pats thread on the other board I was quite convinced that, his is the highest power ive scene made on a NA G8 GT. What NA car has made more power than that? Here is the fist post....
I am so happy, you can't even believe it. Ever since the L92 heads came out, a lot of people think that a cathedral port head can't keep up. I didn't believe it and neither did Tony Mamo from Airflow Research (AFR). I own a 2009 Pontiac G8 with a 6.0L L76 engine. With ARH 1 7/8" headers, FAST 102 intake, Yella Terra 1.85 rockers, ASP 25% UD pulley, and Vararam CAI, the G8 made 397rwhp/395rwtq. This was one of the higher dynoing bolt-on 6.0L G8s. Most 6.0L G8s make in the 420-440rwhp range with bolt ons and a 230/238 cam. The highest number I've seen for a 6.0L G8 automatic has been 470rwhp and this one had ported L92 heads.
Tony Mamo and I decided to go "old school" and take off the Gen IV L92 heads and install a set of AFRs brand new 230 V2 heads. We called this our "Back to the Future Project". I had these heads milled to 65cc chamber so they matched the cc volume of an LS2 head (11.0:1 SCR). Then Tony Mamo did one of his famous porting jobs on a cathedral port FAST 102 intake. We used a fairly mild 231/231 .617/.617" 114LSA +2 advance Comp LSL cam. The gains were staggering: 504rwhp/440rwtq. A gain of 107rwhp/45rwtq. Keep in mind, this is through a locked-up automatic. Most people think that there is little to be gained over L92 heads, but thanks to the huge flow numbers and high airspeed of the AFR 230 and the "mamofied" FAST 102, substantial gains can be had.
There is still more power to be gained with a 102mm throttle body and larger airbox as we were pulling 5-6 kPa vacuum at WOT. Stay tuned for more details on the "Back to the Future Project". There's another 10-15rwhp to be gained with reducing inlet restrictions.
When I read Pats thread on the other board I was quite convinced that, his is the highest power ive scene made on a NA G8 GT. What NA car has made more power than that? Here is the fist post....
I am so happy, you can't even believe it. Ever since the L92 heads came out, a lot of people think that a cathedral port head can't keep up. I didn't believe it and neither did Tony Mamo from Airflow Research (AFR). I own a 2009 Pontiac G8 with a 6.0L L76 engine. With ARH 1 7/8" headers, FAST 102 intake, Yella Terra 1.85 rockers, ASP 25% UD pulley, and Vararam CAI, the G8 made 397rwhp/395rwtq. This was one of the higher dynoing bolt-on 6.0L G8s. Most 6.0L G8s make in the 420-440rwhp range with bolt ons and a 230/238 cam. The highest number I've seen for a 6.0L G8 automatic has been 470rwhp and this one had ported L92 heads.
Tony Mamo and I decided to go "old school" and take off the Gen IV L92 heads and install a set of AFRs brand new 230 V2 heads. We called this our "Back to the Future Project". I had these heads milled to 65cc chamber so they matched the cc volume of an LS2 head (11.0:1 SCR). Then Tony Mamo did one of his famous porting jobs on a cathedral port FAST 102 intake. We used a fairly mild 231/231 .617/.617" 114LSA +2 advance Comp LSL cam. The gains were staggering: 504rwhp/440rwtq. A gain of 107rwhp/45rwtq. Keep in mind, this is through a locked-up automatic. Most people think that there is little to be gained over L92 heads, but thanks to the huge flow numbers and high airspeed of the AFR 230 and the "mamofied" FAST 102, substantial gains can be had.
There is still more power to be gained with a 102mm throttle body and larger airbox as we were pulling 5-6 kPa vacuum at WOT. Stay tuned for more details on the "Back to the Future Project". There's another 10-15rwhp to be gained with reducing inlet restrictions.
I read that thread, he's not the only one finding out that a decent cathedral port will make more power than the ls3 style head. It's hard to change peoples mind sets though when you see ls3 flow numbers and the dollar value on them but they ignore port velocity and etc...
The ls3 blocks with their larger bore seem to benefit more with the larger valved ls3 heads than 6.0 blocked cars.
agreed, seen a friend gain hp after taking his txgiant cam out of his ls3 stroker and dropping in a smaller cam spec'd for the ls3 style heads.
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What you didnt read is how Pat G's NA "Beast" of a car blew up on the track not long after it was built...
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I really dont know any of the details, and as far as I know non were ever posted....I just wanted to throw it out there that that set up that made all that power did pop on the track not long after it was built. I know that for a fact :secret:
I would love to know exactly what went wrong but I have a feeling those details may never be revealed.
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Pat is also selling a product and his car didn't exactly put up the most amazing times for the power it supposedly put down. Cars that Rick has worked on with less actual work done to them are putting up similar times to his "500 rwhp" or whatever it was G8.
Oh, and I had no idea the car blew up. Makes sense. It was running like crap with the horsepower it supposedly made. Doesn't exactly surprise me.
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Also, Rick and Damian are pretty much killing it in this thread. Some serious knowledge bombs. This thread should be ****ing stickied.
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I believe he used a .620"+ lobe and had 12.0 comp. It was a great build and made awesome power but people tend to jump the gun thinking LS3 wont make comparable power. The LS3 is a large volume head which makes it easy to hurt power with duartion and lift. If you wanted to build a matching setup, it would need 12.0 comp and a 223/223 or 227/227 .630+ lift cam on a 112-114LSA+0,+1, ported heads/intake/TB, and all the rest of the hard work he put into his build. You could use a 231/231 cam but it would have to be under .590" lift. I have made impressive power with a 228/228 .598/.589 112+2 cam when using ported H/I/TB. He holds the record so it is hard to argue but have been working on building something close to it if I can ever get time to work on it.
Another thing is the Cathedral intake has shorter runners that helps with power above 6000. The raised runner of the LS3 increases port length and intake arch.
Going back to LS3 heads, I don't see any reason to switch. The heads do very well ported. Can't say how well the cnc'd heads flow. The few CnC'd I have flowed were a little big on the exhaust which hurt flow compared to where it should flow at and they seem to be a little weak .300-.400 on the intake.
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It says .624/.624" but I have read .639/639" also somewhere. Either way, even it is a LSK .643/.643", when going for a kill you don't leave anything on the table......
Just saw this thread so I should clear up some misinformation. When I built my G8 three years ago, I used the best cylinder heads available at the time. There were no hand ported or CNC ported heads & intake that could keep up with the AFR 230 V2 cathedral port heads and ported FAST 102 intake in the power making department. Keep in mind, this was 3 years ago.
Cylinder head technology has advanced since then and now there are some killer splayed valve aftermarket LS3 heads by MAST, PRC and Trick Flow that move the large intake valve away from the chamber wall & cylinder bore and make huge gains in power. These new LS3 aftermarket castings will make more power than the AFR V2 cathedral heads when cammed properly. Like I said, technology marches on. If they were available 3 years ago, I would have run them.
Back to my old G8...it ran a 231/231 .617/.617 114LSA cam ground with Comp LSL lobes. Certainly not LSK lobes. The heads were 65cc so the static compression was right at 11.0:1. Certainly nowhere near 12.0:1. The combo was run with a mild 3200 Yank stall and was never designed to be a drag strip terror. It was a daily driver and a rolling experiment to advancing the cause of combo development for the 6.0L engine. I just chose to follow a different path than most by choosing the cathedral port route. It was my money to risk. The car was never run with a really high stall converter nor did I get the opportunity to run in mine shaft air that would have dropped times even lower than the 11.41 at 122mph. Internet records are not important to me. A good running combo was and I still have not tuned a G8 that had better throttle response and made as much power for such a mild combo as my old G8.
Now to address the part about the car blowing up...you're not hearing the whole story. In February of 2010, I was ready to sell the car so I put in a milder 222/226 .602/.604" 116LSA cam and put back in the stock torque converter and I traded in the car to a local GM dealership. A young man bought the car from the dealership in March 2010 and went off to modding the car and racing it on his own. Nobody knows what exactly happened, but the engine let go under the care of the second owner. Could have been a broken piston, a dropped valve...nobody really knows. The owner of the car dropped in a 454 LSX engine, then had problems with it and had the dealers warranty replace it. The second 454 LSX engine ran great until the car was involved in a terrible accident and was totalled in 2011.
So the engine that failed was not running the combo that made over 500rwhp. It was making about 20-25 less and was more of a stealth combo. So that as they say, is the rest of the story.
Cylinder head technology has advanced since then and now there are some killer splayed valve aftermarket LS3 heads by MAST, PRC and Trick Flow that move the large intake valve away from the chamber wall & cylinder bore and make huge gains in power. These new LS3 aftermarket castings will make more power than the AFR V2 cathedral heads when cammed properly. Like I said, technology marches on. If they were available 3 years ago, I would have run them.
Back to my old G8...it ran a 231/231 .617/.617 114LSA cam ground with Comp LSL lobes. Certainly not LSK lobes. The heads were 65cc so the static compression was right at 11.0:1. Certainly nowhere near 12.0:1. The combo was run with a mild 3200 Yank stall and was never designed to be a drag strip terror. It was a daily driver and a rolling experiment to advancing the cause of combo development for the 6.0L engine. I just chose to follow a different path than most by choosing the cathedral port route. It was my money to risk. The car was never run with a really high stall converter nor did I get the opportunity to run in mine shaft air that would have dropped times even lower than the 11.41 at 122mph. Internet records are not important to me. A good running combo was and I still have not tuned a G8 that had better throttle response and made as much power for such a mild combo as my old G8.
Now to address the part about the car blowing up...you're not hearing the whole story. In February of 2010, I was ready to sell the car so I put in a milder 222/226 .602/.604" 116LSA cam and put back in the stock torque converter and I traded in the car to a local GM dealership. A young man bought the car from the dealership in March 2010 and went off to modding the car and racing it on his own. Nobody knows what exactly happened, but the engine let go under the care of the second owner. Could have been a broken piston, a dropped valve...nobody really knows. The owner of the car dropped in a 454 LSX engine, then had problems with it and had the dealers warranty replace it. The second 454 LSX engine ran great until the car was involved in a terrible accident and was totalled in 2011.
So the engine that failed was not running the combo that made over 500rwhp. It was making about 20-25 less and was more of a stealth combo. So that as they say, is the rest of the story.
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Great info! Thanks for sharing
Now the real question is why you haven't built yourself another one?!?
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Two kids in college (with two more behind them) put a dent in my hot rod fund. One graduates in May so I'm going to use that raise to save up for a C7 Vette. But honestly, I'm so busy working on other people's combos that I rarely have time for my own.
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I fully understand. I see it with Rick C over in our neck of the woods. Its really cool that we have guys like you and him that are truly dedicated to helping other G8'ers out, I for one am very thankful and Im sure many others on here feel the same way. Without y'alls hard work people like me would be dead in the water...Keep up the good work and good luck on the C7.
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