GM valve springs and crate motors

More of an FYI than anything else, I learned something this weekend.

I'm turning an LS376/480 crate motor into a LS376/525. Basically, a 480 is a stock LS3 with a GM "Hot Cam" in it and stock valve springs. A 525 is a stock LS3 with a GM ASA cam and "higher rate valve springs" Yes, that's nearly 100 hp from a cam and spring swap. Gotta love big domestic V8s. FYI, the Hot Cam and the ASA cam have the same 0.525" lift.

Anyhow, I called up GM Performance Parts and got the number for the new valve springs: 12586484. That's a yellow LS6 spring. But it's been replaced with part number 12625033. No worries, you can even buy a cam and spring kit with those springs.

I went to install the 12625033 springs, and they looked exactly like the ones I was pulling out. Not just similar, but identical. I checked further, and whaddya know - 12625033 is the part number for a stock blue LS3 spring. And looking at the spring rates, the older yellow springs had the exact same rates, just with a 0.570" max lift instead of the 0.550" for the LS3.

Just for fun, I peeked under the valve covers of a 525 crate engine. Blue springs. GM, you're busted. You're not changing those springs at all. The 525 just has a cam swap. Which is pretty darn impressive, but still. Makes me wonder why that particular crate is so expensive.

So I spent some money and time, but I learned something. Anyone want to buy a Hot Cam and some LS3 valve springs?

Keith Tanner wrote: Which is pretty darn impressive, but still. Makes me wonder why that particular crate is so expensive.

You're buying crate engines with a warranty, right? That's why. 525 hp is a lot to throw at an engine without knowing how it's going to be used and still have a blanket coverage warranty.

Bryce

That engine is defective. You should give it to me. I'll use it in one of my projec... I mean, dispose of it properly for you.

Well, this particular engine has no warranty anymore. Interesting idea, though, it's simply the warranty cost. It makes sense.

I always figured that particular crate cost more because of the extra labor to swap the valve springs. These things aren't built up in 480 or 525 configuration, they're LS3s off the production line that get new cams.

Crazy to think its just a cam swap for all that extra power.

AquaHusky wrote: Crazy to think its just a cam swap for all that extra power.

Google "LS7 hot cam" one day...

I think the power gains are overstated, the base 430 hp number is a full-boat production SAE test. The 480 and 525 numbers are "aftermarket" numbers, probably tested without all accessories, etc. We've found the 480 cam makes about 20 hp more at the top end than the 430 in our cars.

We haven't tested a 525 yet. But if the delta between the 480 and 525 is consistent, I think it'll be quite a happy cam. I know the ASA cam used in the 525 has delicious throttle response, it's one eager puppy of an engine. That's what sold me on it.