long tube headers on an 2008 4.8 silverado
03-11-2009, 10:21 PM
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should be good for some hps, the freeing part about long tubes is the equal length or close to primaries, helps to balance out the cylinders. Headers will always free up more power than manifolds.
03-12-2009, 07:09 AM
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03-14-2009, 10:49 PM
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Your stock exhaust flows fine unless you really start to modify the engine or consistently run high RPM's. Install an exhaust back pressure gauge and see what you have if you really want to know. According to the last service manual I read, GM called for a maximum BP of 8 psi and that was looking for a partially plugged cat. I bet you won't find more than 1 or 2 psi in your system at wide open throttle. About the only real gains you will see from a cat back is sound.
03-14-2009, 10:55 PM
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Your stock exhaust flows fine unless you really start to modify the engine or consistently run high RPM's. Install an exhaust back pressure gauge and see what you have if you really want to know. According to the last service manual I read, GM called for a maximum BP of 8 psi and that was looking for a partially plugged cat. I bet you won't find more than 1 or 2 psi in your system at wide open throttle. About the only real gains you will see from a cat back is sound.
03-17-2009, 09:55 PM
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By modify I mean:
1) High profile cam
2) Forced induction
3) Bored & stroked
4) High flow heads
Any or all of the above would "modify" your engine and the amount of air passing through it. Once you start to push more air through your engine, you exceed the flow capacity of your exhaust and need to upgrade to make the best of the other modifications.
By just adding headers and/or a cold air intake (CAI) you are improving the volumetric efficiency of your engine and freeing up some horsepower trapped by the inefficient/restrictive manifolds and air intake. This will usually change the power band a bit and show a noticable improvement in horsepower and torque. There will be very little increase in flow through the exhaust and therefore your stock exhaust will work just fine. Hope this helps without rambling.....
1) High profile cam
2) Forced induction
3) Bored & stroked
4) High flow heads
Any or all of the above would "modify" your engine and the amount of air passing through it. Once you start to push more air through your engine, you exceed the flow capacity of your exhaust and need to upgrade to make the best of the other modifications.
By just adding headers and/or a cold air intake (CAI) you are improving the volumetric efficiency of your engine and freeing up some horsepower trapped by the inefficient/restrictive manifolds and air intake. This will usually change the power band a bit and show a noticable improvement in horsepower and torque. There will be very little increase in flow through the exhaust and therefore your stock exhaust will work just fine. Hope this helps without rambling.....