i have seen a bunch of guys running ls7 lifters on their builds but i cant find info as to why. can someone shed some light on this for me?

 

LS7 lifters are basically stock replacements now. They are proven and work well in pretty much all applications .

If you order new factory lifters they will be LS7 lifters , at least thats what SDPC told me when i bought a set.

 

oh ok. i thought maybe they were somehow better than the stock originals

 

^ what he said...

however...the LS7 lifter has a different cup which makes the effective length 0.050" longer than the stock lifter, therefore you need a shorter pushrod for the same preload.
Now...having said that...there are a lot of folks that will argue that stock length are fine with them. Using a PR checker would be best.
I'll see if I can get Damian to chime in on this...

 

+1 on pushrod length checker.

 

As stated above, the LS7 lifter is now the direct replacement for all LSX GM lifters. If you go to any GM parts store in the country and ask for a set of lifters for an "LS1", they're going to give you LS7's.

It's good practice in any fresh build to use fresh lifters, and LS7's are a cheap alternative to some of the other routes. They are ~ .050-.060 taller @ the cup, but through trial and error I've found that it doesn't effect pushrod length as much as you might think. The lifter will "eat up" (so to speak) a good bit of the extra travel.

Camshaft base circle and the amount cut off the heads will have more of an effect on lifter preload. With an LS7 lifter, you want ~.070-.090 of preload, or 1 1/2 - 1 3/4 turns before reaching final TQ (22 ft lbs) while the lifter is on the BASE CIRCLE of the camshaft.

Most of todays aftermarket camshafts with .580 or more lift are going to be shrunk .040-.050 @ the base circle. So go ahead and add an additional .050 of needed travel to the length of your pushrod measure. Whatever the heads are milled to, subtract that number which will give you a much better starting point. IE: .050 shrunk base circle, .025 milled heads = .025 longer pushrod. This is a guide to get you started, this is not the 100% accurate way to measure. Pushrod length checker is required.