Hey, kind of Bringing this thread back to life, I am wanting to change the cam in my 5.7 Vortec, I know on LS1's, you must insert 2 rods to hold the lifters in place when pulling out the old cam. Does this hold true with the L31's? I am looking at a LT4 Hotcam, I'm guessing that I will have to change my valve springs as well, I still have lots of "googling" to do.
"Does this hold true with the L31's? " No.
Manually bring the no 1 cylinder to top dead center, carefully mark the distributor and intake for re-installation. Remove the valve covers, intake manifold after draining the coolant down. ( good luck with the EGR tube, might be handy to have a new one on hand before you start the project )
Loosen off the rockers, remove the pushrods, the 'spider' and dogbones for the lifters, and remove the lifters, it is a good idea to keep them in the same order they came out. ( egg carton or so on ) When re-installing the spider, use blue loctite on the bolts, as well as the cam bolts. The rest is pretty straightforward.
Stock heads can't take much more than around ~ .470" lift without machining the valve guides shorter, as well as reducing the diameter for PC type seals. At the same time, the spring pockets will probably need to be enlarged, depending on the spring package required. More than .470 lift, the valve spring retainers contact the top of the valve guide, however production tolerances vary... it may be even less or slightly more.
The stock computer has a 5200 rpm limiter, there isn't a way around this that I know of other than to swap to a different computer. There isn't much point in selecting a cam that pulls to 6500-7000 rpm, instead find one with a bit shorter duration that will trade off top end power for low end torque.
