Valve spring sanity check
03-02-2013, 02:16 PM
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Valve spring sanity check I'm looking to go with a custom grind cam in my G8 (L76) with LSL intake, LXL exhaust lobes. 215/226 .604/.605, on a 115 +1 or a 116 +2. Daily driver, auto, stock stall, gears. I've chosen the intake valve closing point to give me a dynamic compression ratio of about 8.25:1. I also don't like a lot of overlap, didn't have a good low-speed experience with a 218/230-114 +4 on my LT1, thus the wider LCA....
I'm a pretty big fan of the beehive style valve springs, had a really favorable impression from my 96 LT1 days. Based upon what I've read/researched, the Comp 918's should be able to handle this. To lighten the valvetrain I intend to go with hollow stem LS3 intake valves and Ti retainers. I will also buy hardened pushrods. Re-using stock 1.7 rockers. Recall the L76 is a 6.0L with L92 heads (same as LS3 but solid stem intake valves). Motor is 10.4:1.
Or, if you think I should stay with a dual spring, should I then bother going through with the extra hassle/expense of LS3 valves and Ti retainers? Is there any way to figure how much reduction in valvetrain weight corresponds to required spring rate?
I'm a pretty big fan of the beehive style valve springs, had a really favorable impression from my 96 LT1 days. Based upon what I've read/researched, the Comp 918's should be able to handle this. To lighten the valvetrain I intend to go with hollow stem LS3 intake valves and Ti retainers. I will also buy hardened pushrods. Re-using stock 1.7 rockers. Recall the L76 is a 6.0L with L92 heads (same as LS3 but solid stem intake valves). Motor is 10.4:1.
Or, if you think I should stay with a dual spring, should I then bother going through with the extra hassle/expense of LS3 valves and Ti retainers? Is there any way to figure how much reduction in valvetrain weight corresponds to required spring rate?
Last edited by jgeorger; 03-03-2013 at 08:22 AM.
03-02-2013, 03:01 PM
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Does this combo look okay? Picking a valve spring is not an exact science, since it somewhat depends on how aggressive a ramp a lobe has, which is not quantified in any way. It seems that over the years, ramps have gotten more aggressive, and valve springs have gotten tougher. The LSL lobes are pretty agressive, and I do believe that Comp's own line of LSr cams (using these lobes) recommends a heavier dual spring. However, that recommendation does not take into account valvetrain weight. So I'm just looking for a little consensus. And if anyone has any serious problems with my cam choice, I would like to hear that as well. For example, if someone told me the PCM in my 09 is more tolerant of overlap than my old 96 LT1, I might consider tightening the LCA a bit.
03-02-2013, 04:29 PM
#4
I wouldn't carry over too much of cam theory over on LS3 heads. Different animal IMO
