LS7 head spring pocket depth cutting
Thread Starter
Teching In
Joined: Aug 2018
Posts: 30
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LS7 head spring pocket depth cutting help
what if my spring height was too tall and i had to cut 0.050" extra depth into the spring pocket
my head guy was nervous about it but as of right now he is doing it may have already done it
this is a huge 650 lift solid roller cam w like 450lbs open spring force the pressure in that spring seat must be unreal and aluminum has very **** fatigue life so if it bends at all even minor flexing over a short time thats millions of fatigue cycles
how thick are ls7 heads in that area?
did i just ruin a set if max effort cnc ported ls7 cylinder heads?
please tell me its fine and gm put a ton if extra material there
what if my spring height was too tall and i had to cut 0.050" extra depth into the spring pocket
my head guy was nervous about it but as of right now he is doing it may have already done it
this is a huge 650 lift solid roller cam w like 450lbs open spring force the pressure in that spring seat must be unreal and aluminum has very **** fatigue life so if it bends at all even minor flexing over a short time thats millions of fatigue cycles
how thick are ls7 heads in that area?
did i just ruin a set if max effort cnc ported ls7 cylinder heads?
please tell me its fine and gm put a ton if extra material there
Thread Starter
Teching In
Joined: Aug 2018
Posts: 30
Likes: 1
ahh cool thanks for the help G Atsma
lets assume its Gen V for giggles (unless a mod wants to move my thread for me)
whats the alloy difference between Gen IV and V? crap is there another sub forum when asking a Gen IV / Gev V agnostic question? Again maybe a mod can help
i also wonder if its the same casting methods, i think the V is DI so it may not only be stronger and heat treated differently but also a thicker section so if this is a Gen V, how much if any can i increase seat depth before elastic strains get too high and i have a fatigue fracture? assuming a 450 lb open seat force at 8000 rpm w a solid titanium valve?
ive been told by some racers they have epoxied that area when they cut too deep and crazy enough it survives many race seasons
just looking for some wisdom many thanks Jeff Check
lets assume its Gen V for giggles (unless a mod wants to move my thread for me)
whats the alloy difference between Gen IV and V? crap is there another sub forum when asking a Gen IV / Gev V agnostic question? Again maybe a mod can help
i also wonder if its the same casting methods, i think the V is DI so it may not only be stronger and heat treated differently but also a thicker section so if this is a Gen V, how much if any can i increase seat depth before elastic strains get too high and i have a fatigue fracture? assuming a 450 lb open seat force at 8000 rpm w a solid titanium valve?
ive been told by some racers they have epoxied that area when they cut too deep and crazy enough it survives many race seasons
just looking for some wisdom many thanks Jeff Check
FWIW, 450 lbs spring pressure is no big deal on an aluminum casting. They're pretty thick right there. Also, think about this...
That same 450 spring pressure pushing down on the deck is pushing up on the valve tip. The valve stem will fail before the head just on pure mass and surface area.
I know a guy who ended up over 600 lbs open pressure and the tip flew off the valve. Heads were fine.
All that said I would do what Todd said above. But not out of fear. It is just cheaper and easier to swap springs than machine the heads.
That same 450 spring pressure pushing down on the deck is pushing up on the valve tip. The valve stem will fail before the head just on pure mass and surface area.
I know a guy who ended up over 600 lbs open pressure and the tip flew off the valve. Heads were fine.
All that said I would do what Todd said above. But not out of fear. It is just cheaper and easier to swap springs than machine the heads.
I had 450 pounds of spring pressure open for 10 years on my OEM LS7 and I was able to find springs that were 1.80-1.82 inches tall and could do 650 lift. There are lots of double springs out there that can do the .650 lift. In fact the LS7 head needs a lot shims at 1.80 as they have an installed height of 1.90 when coming from factory with beehive springs. I think I had like .050-.060 of shim under each spring. I would not cut the head because you don't have too - get different springs. Check out the PAC website.
Last edited by Double06; Apr 19, 2020 at 06:29 PM. Reason: adding stuff
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I'm 12K miles in on a set of BTR .660" Platinum springs on my LSX-LS7 heads running a .648" lift hydraulic roller. They are 180 seat and 450 open.
Yes, I had to run shims to get them setup at the correct height/coil bind.
Yes, I had to run shims to get them setup at the correct height/coil bind.
Originally Posted by Greg Hogue
how big in diameter can you cut the pocket for a bigger spring? I need a bigger spring for .800 lift going to try to turn the motor hard
If you need a bigger wider spring you may need to look at the Brodix Big Spring head. That is a Specific Casting for the big spring (like up to 1.50-1.6 inch versus stock 1.3 inch) which might mean that the regular head is not up to that task.
Teching In
Joined: Jun 2014
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From: ALEDO TX
I need to put a bigger spring. Around 400 in seat and 800 rate. Cam is a 278 300 with .780 lift
Last edited by Greg Hogue; May 10, 2020 at 10:22 PM.