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LS6 valves springs on Vortec heads

17K views 13 replies 9 participants last post by  greg85mcss 
#1 ·
LS6 springs on Vortec heads seems like a good mild upgrade/replacement for old stock L31 springs.

My questions are:

  • Which retainers and locks should I use?
  • What is a good seat pressure for a HT383/RamJet cam (GM# 14097395) and stock 1.5:1 rocker arms?

Just noticed those engines come with the softer 10212811 springs with only 80# on seat at 1.200" installed height. So I guess they will also work, although they seem really weak for a roller cam.
 
#2 ·
Yep. GM also uses the same springs on the Ramjet 350 which also uses the "395" cam w/ 1.6 roller rockers for lifts of 460/480.The LS6 springs are a good upgrade.You will need to use the Comp 787 retainers.The LS6 uses 8mm valves stems vs 11/32 of the Vortecs.
 
#3 ·
Just noticed those engines come with the softer 10212811 springs with only 80# on seat at 1.200" installed height. So I guess they will also work, although they seem really weak for a roller cam.
Ummm, I suspect that 1.200" is the valve open height or coil bind height, not the installed height. 80 lbs on-seat pressure would be ok for a mild flat tappet hydraulic cam. Here's an example:
Chevrolet Performance 19154761 Chevrolet Performance Valve Springs - Free Shipping on All Orders @ JEGS
 
#5 · (Edited)
Ummm, I suspect that 1.200" is the valve open height or coil bind height, not the installed height.
Of course. I was late for lunch and consequently had brain fade! Looks like I can't edit a message here, unless it's within xx minutes of posting, right?

Sounds like the lighter springs will work for my application if GM uses them even with 1.6:1 rockers. Will test the springs on the used I heads I just bought. They may be OK as is.
 
#12 ·
Yes, but one thing you may see is the locks sit a little high of the retainer or the retainer is pushed down a little is another way to look at it. This puts the spring under a little more compression which will raise the seat pressure a little, something these springs can use. With an agressive short ramp cam at only 80 pounds of seat pressure the soft spring can allow the valve to bounce as it closes. GM factory cams tend to be rather rampy, that includes their hyd. rollers so this isn't much of a problem for them but an aftermarket cam may not be as happy as many of these cams really shorten the ramp time between zero at ramp threshhold and .050 lift so they drop the valve pretty fast so the spring needs to be strong enough to prevent a valve bounce.

Bogie
 
#13 ·
May want to look into a set of of PAC 1218 springs. They are a good spring for mild cams. A lot of LS guys use them for cam upgrades.

You will need the Comp retainers and locks for the larger diameter SBC valves stems.

Comp Steel Retainers 787-16
Locks 648-16

These will also work with LS6 springs.

I have PAC 1218's on my new 383 build, DART SHP heads.

 
#14 ·
The cam is a flat tappet so I'm not sure how that affects the spring bouncing. From what I have read the zo6 springs are about the right pressure. Been trying to find out about the stock springs since these heads came off a gmpp crate motor & the lift on that cam is more than the stock vortecs should be able to handle. Anyone know if this setup is somehow upgraded? Did gm just throw a big cam onto a motor that shouldn't be able to handle it?
 
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