[Mountain]

It's not as simple as looking at things as "x-RPM" with "stock valves" and "aftermarket cam" with "some kind of valve springs"....

-Particular valve weight
-Particular lifter weight
-Particular pushrod weight
-Particular pushrod stiffness
-Particular cam ramp rate (up and down)
-Particular spring pressure
-Particular redline-RPM

The stock valves are heavy and designed around durability towards a camshaft with fairly mild ramp rates, a redline-RPM of 6,600RPM and mild valve spring pressures, all keeping in mind the stock pushrods and heavy DOD lifters.

Stock valves+higher RPM+stiffer pushrods+very stiff springs... add in aggressive ramp rates and the stock valves won't be very happy.

But... stock valves+higher RPM+stiffer pushrods+stiff-enough springs and a mild ramp rate and the stock valves may be just fine, especially with lighter lifters.

Katech touched on this in some other posts - I would check into their words. Lighter valves and lifters it seems are very smart upgrades if you want more RPM out of the LT1/LT4 from stock.

[Duramacr1]

When I did Ported and milled my heads I went ahead and put solid SS valves in them and they weren’t very expensive . It was cheap insurance for me . I heard bad things about the stock valves and even the place that worked on my heads recommend me changing them and had the stock size valves in stock.

[adamjwilson]

Originally Posted by SnowWhiteSS

Mine aren’t ls7 lifters lol. They’re gm performance racing lifters. Good for 8k rpm tried and true. I have no idea the power yet because I haven’t dynoed the car yet. I haven’t even started it lol. I still have to put the radiator and intake back on and start it. Hoping for mid 500’s with the cam.

If you are looking for the mid 500's then a stock bottom should be fine...
beating those stock valves above 7K consistently is another story with an overly aggressive cam
Take Mike at KaTech and King's advice in previous posts. KaTech is a great vendor to deal with and will provide great guidance for your build.

[18.2SS.1LE]

Originally Posted by SnowWhiteSS

What lifters are you running?

Cadillac Racing lifters. The car sees the rev limiter spinning the tires frequently, as well as many 140+ mph runs. Hasn't missed a beat.

[truth411]

Probably related to this.

https://youtu.be/Ish8wJGU6b4