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Modding to 300 hp

MyPrixGT06

MyPrixGT06

New member
I have a 2006 gt SC. I am going to started on my build and looking to get at or close to 300 hp at the crank (reason being I want to be as fast as the 5.3L). I am running an open cone as of now, thinking about building a CAI. Next on the todo list is headers. So, what 5hp for the intake and 15hp for the headers? That brings me to 280hp? If I follow the guide on "safely modding" to run a 3.6" pulley how much more hp could that give me or that else could I do to safely achieve my goal?
 


300 crank is a very realistic goal. I would add 1.9 modded rockers and be done with it. With a solid tune that should net you damn close if not spot on. From there you could start dropping pulleys to push it even further.
 
Agreed on the rockers. The 5.3 has a much stronger top end than the 3800 and 300hp on the 3800 isn't going to feel like 300 on the 5.3. Rockers will help that though.
 
id say open cone headers (proper spark plug heat range) 3.4'' pulley and a good tune should get you about 300BHP
 


ok whoops my bad i didnt read that part ok just change 3.4'' to 3.6'' and you should get a 300hp then i was thinking 97-03 thats what i have and thats my 300hp build
 
300 is easy... it's over 300 where things start to get tough.
mike, what do u mean the v8 has more 'top end'? I was always confused about what people mean by that.
 


SnowFlake said:
300 is easy... it's over 300 where things start to get tough.
mike, what do u mean the v8 has more 'top end'? I was always confused about what people mean by that.
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It doesn't fall on it's face in the upper rpm's like the 3800 does. Pit your average bolt-on modded 300 crank horsepower 3800 against against a Grand Prix GXP and the GXP will pull away every time.

But you need valvetrain mods to make 300bhp... even if it's just 1.9s, right?
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Generally not with the modded stock rockers but as the cars age it's definitely smart to change the valve springs.
 
Mike Kopstain said:
It doesn't fall on it's face in the upper rpm's like the 3800 does. Pit your average bolt-on modded 300 crank horsepower 3800 against against a Grand Prix GXP and the GXP will pull away every time.
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I'm still confused, is this a gearing thing or a power curve type thing?
 


Nixon said:
Power curve due to the cam.
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So what you guys are saying is that if we compared a mild bolt on gp with 1.9s that makes the same whp as a stock LS4 that the LS4 will make it's peak tq and peak hp higher in the RPM range relative to the L67 and it will carry decisively more power into the redline?

Am I on the right track?
 
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