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valves ?

5K views 16 replies 10 participants last post by  danswrld 
#1 ·
Hi

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

thanks
 
#3 ·
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.
 
#5 ·
valve sping is more important in valve control during high rpm...valve float is no joke.
 
#6 ·
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.
 
#7 ·
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.
 
#8 ·
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.
 
#9 ·
Would there be any benefit to changing valves to the lighter weight LS3 valves?
Tate
 
#11 · (Edited)
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.
 
#17 ·
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".
 
#14 ·
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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