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780 Posts
New mechanic ??
The L76 stock has the same part number injector as the LS3 and the LS7 .
My LS7 makes near 560 RWHP with stock 58 psi fuel pressure and stock injectors.
 

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2009 MGM GT. In need of wider tires and LSA
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79 Posts
Whats the AFR when going WOT?
Gonna go out on a limb and say your mechanic doesn't know either. To me the only way to know for sure is to look at injector duty cycle and AFR.


Only if the injectors are close to maxed and you're still going lean then maybe injectors are the problem.
 

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VE SSV commodore series 1 sport wagon
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20 Posts
Without knowing the flow rate of your heads it’s hard say and a cam will also change the AFM. Stock heads will handle decent flow for example LS3 heads in stock form are good without mods.
A cam and trunnions upgrade with lifters will see more power and you won’t have to change injectors or fuel pump staying below 500 hp @ flywheel. Anymore gains above 500hp @ flywheel will require injector upgrade ,fuel pump , and heads package for NA ,if you boost then definitely need injectors and fuel pump with blower friendly cam of Lobe separation angle (LSA ) of between 114 to 118 degrees if you go wider with LSA on the cam then you bleed off boost. An NA cam with LSA of 12 - 14 is lumpy enough for street use and suits the comp ratio of the LS in standard form ,however a trunnion upgrade and tune would be a start and depending on the cam ,which is the heart beat of the motor a wider LSA grind will benefit from head work.

I build a 408 stroke from LS 2 with Cam LSA of 113 degrees with Higgins LS3 ported heads and made a modest 357kw (478hp) at the wheels with no injector upgrade , but I did change the fuel pump. My VZ SS was the same year as the 2004 GTO. I later supercharged this car with Harrop 2300 without changing the cam and made a modest gain on 8lbs boost of422RWKs (565hp ) but I had to change injectors and upgrade the pump again but the wider LSA on the cam meant for NA bled boost ,so had to change to a smaller pulley.

Long story short is plan your build for either Boost or NA with an intention of a stroker or boost ready cam of LSA of 114 - 118 degrees and you will still pull decent power NA on that cam spec prior to going boost.

Stay away from fancy manifolds as the LS manifold is a proven winner and not many gains from after market manifolds are worth the effort at most you gain from aftermarket manifold 2to 3hp at the high end and as a street car how long do want spend in 4000 to 6000 rpm range.

Boost is an LS engine friend and I never regret going boosted and power and torque on tap.

Happy to share many of Mis adventures and with building engines and the expensive mistakes I made chasing HP. A little research goes along way to saving money and still getting great gains with the right streetable LS package in NA and boosted. The LS engine is by far the best engine I have ever built and so easy in stock form to with easy mods to pull decent reliable numbers.

Thanks for reading if your got this far

Pete
 

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I didn't catch who did the install? I threw a cam and heads on an ls3 and the car ran almost normal before the tune after finding that I unknowingly damaged a sensor wire.
Sometimes it's better to start with the basics. Air, fuel and spark. You have either to much or to little fuel and or air. Vacuum leaks, cracked plenum, worn, wires or wiring, fuel pressure...
Just curious to what codes are present.
 
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