As mentioned above, pretty much any cam upgrade is gonna want some new springs, the stockers won't handle alot of lift or an agressive ramp rate. Even my baby cam (Comp 206/212 515/520 114) required a spring swap. If price is a concern, you can get some yellow LS6 spings from SDPC (sponsor) for around $60-$70. I recommend investing in the Crane/VHP valve spring compressor...it's a tad pricey, but it makes the job a piece of cake

 

I have the crane cams tool, love it worth its wieght in gold. don't make the mistake I did and do a cam before a good converter

 

I read in a Hot Rod magazine that the stock heads wouldn't allow more lift than .475" without hitting the retainers on the valve guides. Without machining the valve guides how are ya'll getting by this?

 

Im running a 577 lift on a 5.3 no problems here. never heard that before

 

#54-408-11

Camshaft Specification Table
Part Number 54-408-11
Engine 1997-Present General Motors
4.8ltr-6ltr
Gen III/LS1/LS2/LS6,
8cyl.
Grind Number LS1 XR259HR-12
Description
Intake Exhaust
Valve Adjustment 0 0
Gross Valve Lift 0.515 0.522
Duration At 0.006 Tappet Lift 259 265
Valve Timing At 0.006
Open Close
Intake 20 59
Exhaust 67 18
These Specs Are For The Cam Installed At 110 Intake CL
Intake Exhaust
Duration At 0.05 206 212
Lobe Lift 0.303 0.307
Lobe Separation 112
Recommended Valve Springs 941-16
-15 overlap @ .050 will idle well
check your height for stock springs or get the ls6 springs but thats what Id go with for stock rpm range/stall

 

I ran 600 lift on the stock 5.3 heads, no machine work. To make it even better, I think I was using ls6 springs at that!