liftin'em on nittos

iTrader: (2)

i have done a little research and am to the point where it's just a matter of opinion on what to choose. so i'm asking you guys with over .725" lift what springs/retainers you're using, what machine work had to be done to the head and rocker arm (as well as what brand rocker arm you're using.) thanks for any input.

383LQ4SS

iTrader: (33)

Do you have heads already? Do you have valves?
Best to get with the head shop that will be doing the setup.

My advice is to get the biggest OD spring pocket you can get. Preferably 1.620 or bigger. You will have to go with some pretty long valves to get this because you cant machine the pockets on the intake side very deep before you break through.

I dont even know if its possible to get he LS1 head to accept a 1.620+ spring pocket. But if your head guy thinks he can do it i would give it a shot. If you can get a spring pocket that big and then a valve long enough to give you a 2.00 installed height...there are a ton of good springs out there that can handle the job of .730 lift.

My heads have 1.57 spring pockets cut as deep as we could get them and the valves are .100 longer than stock. This allowed for a spring setup of a 1.900 installed height max. I tried a Lunati spring that was on the tight side. They seemd to be working ok on my old 385 ci motor. But after it spun a bearing the PtoV contact busted that spring.
So then I got the HPE 415 ci motor and tried some Comp 999s. I installed them at approx 1.875 installed height that should have netted about 210 seat pressure and a max usable lift around .750. The spring pressure was on the light side as recomended by the cam grinder.

I broke a few of the Comp 999s within about 500 miles. I pulled out one of the still intact 999s and checked the spring pressure at the 1.870 installed height and they were reading about 160 lbs about 60 lbs short of where i really needed to be.

So looking through all the available spring charts out there it was apparent I was right on the edge using a 1.550 OD spring at a 1.900 installed hieght. There just werent many springs out there. So I bought some +.050 locks that move the retainer up .050. I now have room for 1.950 installed height. This allowed me to get into a whole different realm of available springs. I went with some Comp 932s ( I believe that was the PN) and this time we measured the spring pressures on the seat and open before installing them. One note....if you check your spring pressure and actual coil bind measurements before installing...be sure to check them with your retainer ontop of the spring. This will change the actual coil bind measurement and pressure slightly.

So when we measured my new Comp 932s...actual coil bind was 1.135. Installed height was shimmed to 1.935. That gives .800 max available lift before coil bind. Subtract .060 for minimum space before coil bind and that leaves .740 usable lift on my current setup. My cam is .731/.714. Tested spring pressure at 1.935 was approx 230 on the seat and open pressure will be a little over 550 lbs.

Be sure to measure your ACTUAL valve lift at the valve/retainer when spinning the motor over. My cam is .731 but different lash and differing geometries can change that quite a bit. Currently at the valve I am getting about .739 lift on the intake.

Comp springs seem to be hit or miss. I have heard good things about the PSI springs but they are expensive. Lunati makes some, and so does K-Motion.

Just do yourself a favor and think about all this and plan it out with your head guy. Also conslut the cam grinder to see what minimum spring pressures he wants to see with the setup.