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post #1 of 17 (permalink) Old 11-20-2010, 03:42 PM Thread Starter
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valves ?

Hi

If I want to rev over 6000rpm I only need to change valve springs what about the intake valves ?

thanks
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post #2 of 17 (permalink) Old 11-20-2010, 06:43 PM
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Cam might need to be changed too.

Just remember there are trade offs whenever you make big changes like this.

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post #3 of 17 (permalink) Old 11-21-2010, 10:30 AM
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Hi

If I want to rev over 6000rpm I only need to change valve springs what about the intake valves ?

thanks
Do you have the L76 engine with AFM/DOD, or the non-DOD variant?

I would think that would make a big difference in our responses. Non-DOD engines are much happier revving higher safely than DOD equipped engines.

At the very least, if you have a DOD engine like the L76 in your Lumina, you'd want to replace the camshaft with a non-dod higher lift cam, replace the special DOD lifters with their LS2 variants, and plug up the extra oil valleys in the tray. You'd be basically changing your L76 into an LS2, more or less.


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post #4 of 17 (permalink) Old 11-21-2010, 02:15 PM Thread Starter
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I have a g8 gt 2009

well I am asking if I can revs over 6000rpm with stock valve springs and stock intake valve ?

my main question is do I need the intake valves does it need to be changed
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post #5 of 17 (permalink) Old 11-21-2010, 04:27 PM
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valve sping is more important in valve control during high rpm...valve float is no joke.
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post #6 of 17 (permalink) Old 11-21-2010, 05:15 PM
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You dont need to run over 6000 rpm on the stock cam it doent make any power up that high. If you are going to install an aftermarket cam then you will have to replace the valvesprings along with several other parts anyway. The L76 does use really heavy valves so having a strong spring to control the valvetrain is essential.

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post #7 of 17 (permalink) Old 11-21-2010, 10:49 PM
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You can successfully run the stock valvetrain to 6200 and still make power before it starts floating. Not to mention it's not necessary since the stock engine doesn't make any power past that.

On the A6 cars I tune, I set the shift points in the 61-6200 range. This makes a big difference in getting the car down the track/road faster because it doesn't fall as far back in the rpm range after each shift.

6200 is fine. Anything north of that is pointless AND risky.

As for upgrading valves, that is not necessary.

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post #8 of 17 (permalink) Old 11-22-2010, 02:42 AM
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The roller lifters in the AFM motors are very heavy in order to accommodate the DOD oiling in order to collapse the lifter in four cylinder mode. The cam is also small compared to other LS engines partly because the lifter can not take an aggressive ramp profile due to it's weight. Changing springs alone most likely will not get the desired result to rev the motor safely, and as previous post stated, the motor falls off in the power band mush past 6,200 range due to the conservative cam profile. A more aggressive cam, AFM delete lifters and matching springs (such as a stock LS3 cam and lifter set even) will get the motor to 6,500 no problem.

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post #9 of 17 (permalink) Old 11-22-2010, 06:16 AM
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Would there be any benefit to changing valves to the lighter weight LS3 valves?
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post #10 of 17 (permalink) Old 11-22-2010, 07:23 AM Thread Starter
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thanks
what about the valves do I need to go for ls3 hollow stem valves
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post #11 of 17 (permalink) Old 11-22-2010, 07:52 AM
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Quote:
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Hi

If I want to rev over 6000rpm I only need to change valve springs what about the intake valves ?

thanks

Consider changing the pistons too. That is one of the biggest chunk of reciprocating mass and I do not think the Stock pistons are designed to handle stress at that amount of RPMs. By my experience, most cars with V8 over the 5.0 L mark are not high revving, they have bottomless torque at lower RPMs. In another hand, the ones that climb way high RPMs has puny size pistons.

This might give you an idea on what to look for.

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Last edited by Richard Craneum; 11-22-2010 at 08:02 AM.
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post #12 of 17 (permalink) Old 11-22-2010, 09:27 AM
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Consider changing the pistons too.
I'll second that motion, especially if you have the L76. It was initially a truck motor, and still has its truck pistons. Some pistons designed for higher RPM's and loads would be a nice change if you can do it.

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post #13 of 17 (permalink) Old 11-23-2010, 03:07 AM Thread Starter
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so it is not necessary to replace the valves but when do I need to replace them and maybe go with ls3 valves (lighter)
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post #14 of 17 (permalink) Old 11-23-2010, 08:22 AM
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G8 GT it means same as our Lumina Ss in UAE, so I will not recommend more than 6200 rmp because you have the L98 valve springs, you can go for 6600 if you put the LS2 valve springs. google the part number and get them from any dealer.

this is the best for you and based on my experience.

regards

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post #15 of 17 (permalink) Old 11-24-2010, 09:36 PM
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Originally Posted by Richard Craneum View Post
Consider changing the pistons too. That is one of the biggest chunk of reciprocating mass and I do not think the Stock pistons are designed to handle stress at that amount of RPMs. By my experience, most cars with V8 over the 5.0 L mark are not high revving, they have bottomless torque at lower RPMs. In another hand, the ones that climb way high RPMs has puny size pistons.

This might give you an idea on what to look for.
With all due respect sir, that is horrible advice to give about an LS engine. Especially on the internet where 350 people who don't know any better are going to believe it and read it.

You do NOT "need" to change the pistons in any LS motor unless it's getting a lot of boost or a lot of nitrous. I've spun stock LS bottom ends to 7200rpm's and pushed 200 shots of nitrous through them. The stock pistons are fine.

Yes, lighter pistons are a benefit. But necessary? Absolutely not.

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post #16 of 17 (permalink) Old 11-24-2010, 09:43 PM
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With all due respect, the word Consider does not meant that you have to.

Hey, if you have experience in the matter do not hesitate to share

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post #17 of 17 (permalink) Old 11-25-2010, 12:28 AM
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so it is not necessary to replace the valves but when do I need to replace them and maybe go with ls3 valves (lighter)

If the sole goal is to rev the motor past 6,000 rpm, it is all in the cam, lifter, and valvesprings.....not the valves themselves. A more aggressive cam is going to move the powerband into the upper rpm ranges. Not sure if you are mistaking the term "valves" for "Lifters".

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