Factory Valve spring differences?

[NikolaiD]

I searched for a while now with no good info.

What is the difference between the yellow and blue valve springs?

The engine came with yellow springs, I just bought GMPP heads and they came with blue springs.
I can find specs on the blue springs everywhere, but nothing on the yellow.

The blue say "Outside Diameter: 1.290 in., Coil Bind Height: 1.220 in, Spring Rate: 375 lbs./in.

I thought I found them years ago, but now they're nowhere. Are they the same, just different color? I recall seeing 375lbs./in on the yellow springs too, is that correct?

[frankwjr]

Do your self a favor and replace them with PAC or PSI beehives...and better P/R too...good luck...

BTW - the blue were better but still only rated for stock cam...

[NikolaiD]

I have PAC springs in it, I'm curious about the GM springs. And if the stock cam has .551 lift, why are they using a spring that says "max .550 lift"? Am I over looking something there?

[Russell James]

They don't coil bind at 1 thou over the lift limit. Still plenty of thou's coil clearance. They even use them with the LS7 cam which with LS3 rockers will be at .558" Springs actually work best near coil bind, relatively near, not only a couple thou clearance. I.E. I wouldn't use .575" lift with those blues.

The blues are better than the yellow, the COPO motors go one step better and use the PSI beehive ML.

[christianchevell]

My blue springs went right into the scrap bin. And yes they are not rated at the stock bump sticks specs...... just a throw away unless you are desperate running like the ASA or other low lift cam.....525 lower..... and without a back up being beehive not that great for security of the upper valve train....

[NikolaiD]

Thanks, yeah, I looked at the actual travel with the rockers installed for bind and it seems like there's WAY more clearance then they're spec'd at, but I didn't want to take any chances.

And speaking of specs, I gotta give props to the GMPP heads... They advertise 10% more airflow and my AFRs went from 12.8 to 14.1 from 3000 rpm to redline... I wasn't expecting it to be right on the money.

[christianchevell]

Yes I generally think of beehives as being better for high revs yet mild cammed engines..... and being singles having to change them out like duals most likely a must for longevity from what I learned.