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

 

LS7 is Gen IV, not V

 

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

 

I wouldn’t cut it. Get the correct springs. .650 is no problem with the correct stuff.

 

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.

 

Why would you cut the spring pockets for only .650 lift? For that lift there is easily the correct retainer/spring/collet available to get the correct installed height and pressures you want.

 

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.

 

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

 

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.

 

Greg you might know better than most on here about that. I hope someone chimes in that can answer. Free bump

 

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.

 

i have a Edelbrock LS R Big Johnson headed motor in development. This is going to be a 9000 rpm 900 hp practice engine. Had the core motor and thought it would be a cool project.
I need to put a bigger spring. Around 400 in seat and 800 rate. Cam is a 278 300 with .780 lift