do i need porting - Pontiac G8 Forum: G8 Forums - G8Board.com
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post #1 of 16 (permalink) Old 01-18-2018, 06:18 PM Thread Starter
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do i need porting

so i bought a cam from lingenfelter gt12 "227/235 duration @ .050 lift - .614/.621 lift with 1.7 rocker" and i am just wondering would you guys recommend porting the head and change intake valve if yes which intake valve?

the car is 2009 g8 gt it has cai, full exhaust system, deleted dod and soon cam when i am done i will post a video
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post #2 of 16 (permalink) Old 01-18-2018, 06:41 PM
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I priced it out with Advanced Induction. It's pricey, and for the street it just wasn't worth it.

'09 PSM G8 GT - OPG Intake, DOD-Delete w/ Stage 1C 218/229 .600 Lift 117.5LSA, Kooks 1 7/8 Mids, Solo Axle-Back w/ X-Pipe, SuperPro Bushings (Front and Rear). BMR Sway Bars (Red)
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post #3 of 16 (permalink) Old 01-18-2018, 06:53 PM Thread Starter
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how much hp did you gain
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post #4 of 16 (permalink) Old 01-18-2018, 07:03 PM
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I elected not to port them. It was about $1,100 bucks for the porting job you'd want.

Sorry, that was unclear how they put it. I just meant that I priced it out and elected not to do it since it's just a street car.

'09 PSM G8 GT - OPG Intake, DOD-Delete w/ Stage 1C 218/229 .600 Lift 117.5LSA, Kooks 1 7/8 Mids, Solo Axle-Back w/ X-Pipe, SuperPro Bushings (Front and Rear). BMR Sway Bars (Red)
Power: 400HP/392TQ


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post #5 of 16 (permalink) Old 01-18-2018, 07:14 PM Thread Starter
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oh ok
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post #6 of 16 (permalink) Old 01-18-2018, 09:58 PM
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Not where I would spend my money, our heads flow good enough. Get the LS3 intake valves they will rev higher and you can utilized that with the cam. Get them backcut and maybe a good 3 angle valve job.

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post #7 of 16 (permalink) Old 01-19-2018, 06:20 AM
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And mill the heads to get the CR up.


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2009 SRM G8 GT, GMPP CNC heads milled .035", RCR backcut intake valves, RCR Lunati 219/223 .612/.615 112+1, PSI 1511ML springs, Ti retainers, BTR 7.375 pushrods, Straub trunion bushings, RCR Airram intake, IWIS chain, Melling hi-vol hi-pressure oil pump, oil bypass blockoff, LS7 MAF in Spectre 4", Blox velocity stack, Rotofab, Kooks 1-3/4" LT's, Kooks catted X, Hooker Maxflow axlebacks. 426/383.
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post #8 of 16 (permalink) Old 01-19-2018, 08:36 AM
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And mill the heads to get the CR up.


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Yep, milling them will raise the Compression. How about "Pocket Porting the heads", that can't cost that much. A full on Porting job, yes. A tuner would give the best advice on the "Pro's & Con's" of the outcome.
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post #9 of 16 (permalink) Old 01-19-2018, 09:16 AM
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Originally Posted by G8 GoaT View Post
Yep, milling them will raise the Compression. How about "Pocket Porting the heads", that can't cost that much. A full on Porting job, yes. A tuner would give the best advice on the "Pro's & Con's" of the outcome.
It's still spending money just to spend money. L92s are not going to benefit much from porting anyways until you get into forced induction where you need to enhance the flow.

It would maybe be half the cost, but then you might find negligible gains. That money is best spent elsewhere.

'09 PSM G8 GT - OPG Intake, DOD-Delete w/ Stage 1C 218/229 .600 Lift 117.5LSA, Kooks 1 7/8 Mids, Solo Axle-Back w/ X-Pipe, SuperPro Bushings (Front and Rear). BMR Sway Bars (Red)
Power: 400HP/392TQ


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post #10 of 16 (permalink) Old 01-19-2018, 10:23 AM
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How about the RCR Airram intake? Most people feel it is worthy, based mostly on track numbers. I bought one.

2009 SRM G8 GT, GMPP CNC heads milled .035", RCR backcut intake valves, RCR Lunati 219/223 .612/.615 112+1, PSI 1511ML springs, Ti retainers, BTR 7.375 pushrods, Straub trunion bushings, RCR Airram intake, IWIS chain, Melling hi-vol hi-pressure oil pump, oil bypass blockoff, LS7 MAF in Spectre 4", Blox velocity stack, Rotofab, Kooks 1-3/4" LT's, Kooks catted X, Hooker Maxflow axlebacks. 426/383.
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post #11 of 16 (permalink) Old 01-19-2018, 12:15 PM
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It's still spending money just to spend money. L92s are not going to benefit much from porting anyways until you get into forced induction where you need to enhance the flow.

It would maybe be half the cost, but then you might find negligible gains. That money is best spent elsewhere.

Hold the fort, '09 G8/GT had a L76, not L92. Same bottom end I'm presuming, but the Induction was different correct?
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post #12 of 16 (permalink) Old 01-19-2018, 12:50 PM
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Originally Posted by G8 GoaT View Post
Hold the fort, '09 G8/GT had a L76, not L92. Same bottom end I'm presuming, but the Induction was different correct?
The L76 uses the base LS2 block with an increased bore and AFM channels (I am not clear on other modifications). Also, it utilizes the LS3 Intake Manifold and the L92 cylinder heads. Since we were talking about head porting, I was referring to the heads being L92. Casting 821.

Essentially, it was the culmination of the best from the Gen III Platform; quite a solid motor.
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'09 PSM G8 GT - OPG Intake, DOD-Delete w/ Stage 1C 218/229 .600 Lift 117.5LSA, Kooks 1 7/8 Mids, Solo Axle-Back w/ X-Pipe, SuperPro Bushings (Front and Rear). BMR Sway Bars (Red)
Power: 400HP/392TQ


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post #13 of 16 (permalink) Old 01-19-2018, 04:15 PM
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LS3 heads "almost" flow too much as they are stock. Porting to increase flow isnt necessarily a good thing if it slows down your intake velocities, which can and will effect power, especially under the curve. It can actually have a negative effect. Now some people will argue they made X amount more HP on the dyno at X rpm, but generally the gains are negligible and are usually at the upper RPM range where you dont spend much time. The 4" bore is a little on the small side for LS3 heads, they work better with 4.065 and larger bores. Unless your going forced induction, stroker, larger bore or a combination of those, i wouldn't bother. The cost vs HP gain just isnt worth it.

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2009 G8 GT - Self Built - Kooks 1 7/8" LT, Catted connection Pipes, Corsa Cat Back Exhaust, VCM OTR, LS7 MAF, Custom Cam w/ DoD Delete, Ferrea L92 Hollow Stem Intake Valves, PSI 1511ML Valve Springs, LS7 Lifters, Cometic .040" Head Gaskets, Cloyes Hex-a-Just timing gear, 7.350" Comp Cams Magnum Pushrods, Flycut Pistons, 11.45:1 Compression, HP/TQ TBD, Pat G tuned.
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post #14 of 16 (permalink) Old 01-19-2018, 08:58 PM
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Originally Posted by jgeorger View Post
And mill the heads to get the CR up.
Yes definitely mill the heads, These motor love the increased compression. Can't believe I didn't mention that. RCR modified intake manifold didn't get mentioned either and is definitely money well spent.

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Rotofab CAI, Kook's 1 3/4 LTs, HF Cats, 3" X-pipe, GXP Mufflers, PLX WB O2 & Aeroforce gauges
Rick C Manifold/TB/LS3 valves/Little Lunati/Tune, BTR Spring kit, many appearance mods
VMR Solar Rain V701 Staggered 19x9.5+50 & 19x8.5+35, Hankook V12 285/35 & 255/40
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post #15 of 16 (permalink) Old 01-19-2018, 09:12 PM
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If your milling the heads, you should be checking PTV clearance. There isn't a whole lot of room to cut depending on cam selection. You should be checking PTV clearance even without milling the heads. I had my heads milled .024" and had to eyebrow my piston for clearance. This was to get 11.5:1 compression on a CamMotion cam 220/224 111+1. Part of that was I used different intake valves that took up some PTV clearance. You will never know unless you actually check. I'm betting most people don't check and have no idea how close the really are to piston contact.

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2009 G8 GT - Self Built - Kooks 1 7/8" LT, Catted connection Pipes, Corsa Cat Back Exhaust, VCM OTR, LS7 MAF, Custom Cam w/ DoD Delete, Ferrea L92 Hollow Stem Intake Valves, PSI 1511ML Valve Springs, LS7 Lifters, Cometic .040" Head Gaskets, Cloyes Hex-a-Just timing gear, 7.350" Comp Cams Magnum Pushrods, Flycut Pistons, 11.45:1 Compression, HP/TQ TBD, Pat G tuned.
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post #16 of 16 (permalink) Old 01-20-2018, 08:14 AM
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PTV is why I contacted Rick and went with his recommendations on cam and how much to mill the heads. I had never measured PTV before, but I went through it and with my setup I am near the minimums of .080 and .100" with untouched pistons & stock head gasket.
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2009 SRM G8 GT, GMPP CNC heads milled .035", RCR backcut intake valves, RCR Lunati 219/223 .612/.615 112+1, PSI 1511ML springs, Ti retainers, BTR 7.375 pushrods, Straub trunion bushings, RCR Airram intake, IWIS chain, Melling hi-vol hi-pressure oil pump, oil bypass blockoff, LS7 MAF in Spectre 4", Blox velocity stack, Rotofab, Kooks 1-3/4" LT's, Kooks catted X, Hooker Maxflow axlebacks. 426/383.
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