I just finished installing a Cam Motion stage 2 5.3L cam in my 2008 Sierra LH6. I deleted the DOD lifters and installed LS7 lifters. As for Springs I opted to throw in a set of GMPP 12499224 Blue LS6 springs and a set of 7.400" TSP hardened PRs I had laying around from my RX7 project. The truck 5.3L is stock otherwise.

Truck runs great! However I have a set of Comp Cam Ultra Pro Magnum 1.8:1 rockers on hand that I am thinking of installing.

I have already calculated what my new lift will be it is more then safe for PTV clearance. My only concern is if the LS6 springs are going to be able to handle the increased effects of the rockers. I have been trying to read and study on the effects of duration increased with higher ratio rockers and the dangers of spring coil bind and all the other precautions when doing this mod. I just want to ask some of you more experienced gearheads for any advice or info you may know.

Here are the cam specs: @ .050 duration is 210/215. Lift with 1.7 is .517/.510 (.548/.540 with 1.8 rockers). LSA is 114. Intake center line is 110

Specs for the GM 12499224 springs are: Coil bind height 1.085. Spring rate 375 lbs/in 90lbs @ 1.8" 295lbs @ 1.250. 0.570" max lift.


I think I won't have any issues but never hurts to ask.

Any of you have a formula to calculate increased duration based off of these cam specs and new rocker ratio?

I talked to Kip at Cam Motion and he didn't see any issue, only mentioned to small duration issue may cause a very very small drop in low end power breifly.

Thanks for your time all.

 

I wouldn't recommend those springs rather some PAC 1215's. It's a better/higher quality spring that will outlast the stocker springs.

Check the PR length do not assume 7.4 is correct.

 

sell the rockers and get some headers. less headache, more power, no stress on parts.