Biggest spring OD on stock LS3 heads?
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Biggest spring OD on stock LS3 heads? Hi,
What’s the largest valve spring diameter that will fit stock LS3 heads without machining? Im looking for something to hold that valve on 9K RPM maybe less if its hard to find suitable springs
Thanks.
What’s the largest valve spring diameter that will fit stock LS3 heads without machining? Im looking for something to hold that valve on 9K RPM maybe less if its hard to find suitable springs
Thanks.
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What I’m saying is that valvesprings are the least of your worries…the camshaft guy that designs the cam will have to spec them. It takes a lot of design work and a lot of money to get to 9k rpm. Not an easy task at all.
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Ok…for a 9k rpm build, you’re looking at a complete endurance style build. Oiling setup is dry sump. Aftermarket heads that flow huge numbers, longer valves for the amount of spring required, etc.. Jesel steel or equivalent rockers. Dual throttle bodies on a custom intake setup. Camshaft with .800 lift numbers. You’ll want an aftermarket block with priority main oiling to last.
What I’m saying is that valvesprings are the least of your worries…the camshaft guy that designs the cam will have to spec them. It takes a lot of design work and a lot of money to get to 9k rpm. Not an easy task at all.
What I’m saying is that valvesprings are the least of your worries…the camshaft guy that designs the cam will have to spec them. It takes a lot of design work and a lot of money to get to 9k rpm. Not an easy task at all.
here is the breakdown for my setup
short stroke 3.27”
dry sump
DLC pins
4.125 bore
034 gasket
heads cnc ported with upgraded guides and seats
ferrea hollow stem valves int/exh
jesel solid lifters
T&D shaft rockers 1.8
camshaft 0.657 lift
coated extra clearance bearings on rods and mains
Last edited by R35Q8; Sep 24, 2025 at 04:50 PM.
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From my point of view, if there’s enough space to fit stronger springs without having to machine the heads, that’s the better option for me
here is the breakdown for my setup
short stroke 2.7”
dry sump
DLC pins
4.125 bore
034 gasket
heads cnc ported with upgraded guides and seats
ferrea hollow stem valves int/exh
jesel solid lifters
T&D shaft rockers 1.8
camshaft 0.657 lift
coated extra clearance bearings on rods and mains
short stroke 2.7”
dry sump
DLC pins
4.125 bore
034 gasket
heads cnc ported with upgraded guides and seats
ferrea hollow stem valves int/exh
jesel solid lifters
T&D shaft rockers 1.8
camshaft 0.657 lift
coated extra clearance bearings on rods and mains
here is the breakdown for my setup
short stroke 3.27”
dry sump
DLC pins
4.125 bore
034 gasket
heads cnc ported with upgraded guides and seats
ferrea hollow stem valves int/exh
jesel solid lifters
T&D shaft rockers 1.8
camshaft 0.657 lift
coated extra clearance bearings on rods and mains
short stroke 3.27”
dry sump
DLC pins
4.125 bore
034 gasket
heads cnc ported with upgraded guides and seats
ferrea hollow stem valves int/exh
jesel solid lifters
T&D shaft rockers 1.8
camshaft 0.657 lift
coated extra clearance bearings on rods and mains
I’d like to know what intake as well, and what size TB’s. Also wonder who’s working the LS3 heads for this project. I’ve seen several guys both here on Tech, and on another site attempt to build a setup just like this, with the LS platform. You really need to move the lifters in the block to do this reliably, as you’ll need a big pushrod. An .850” diameter lifter wheel will help with camshaft lobe profile a ton, which means a .937” lifter body. Jesel makes them, as does LSM, Xceldyne, and Morel. Takes a lot of airflow to go 9k+ rpm. We did it in the cup world in the 90’s, (flat tappet lifters to boot) so it’s not anything new, you just have to cross your t’s and dot your i’s or you’ll end up with a dyno room full of shrapnel and oil everywhere. The jump from 8k rpm to 9k rpm is a huge step in innovation and financial commitment.
I’d like to know what intake as well, and what size TB’s. Also wonder who’s working the LS3 heads for this project. I’ve seen several guys both here on Tech, and on another site attempt to build a setup just like this, with the LS platform. You really need to move the lifters in the block to do this reliably, as you’ll need a big pushrod. An .850” diameter lifter wheel will help with camshaft lobe profile a ton, which means a .937” lifter body. Jesel makes them, as does LSM, Xceldyne, and Morel. Takes a lot of airflow to go 9k+ rpm. We did it in the cup world in the 90’s, (flat tappet lifters to boot) so it’s not anything new, you just have to cross your t’s and dot your i’s or you’ll end up with a dyno room full of shrapnel and oil everywhere. The jump from 8k rpm to 9k rpm is a huge step in innovation and financial commitment.
Thread Starter
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Your parts list isn't bad, but some details can make it better. With that much bore dia put a bigger intake valve in the head, like a 2.185 or 2.20. I think Ferrea makes a drop in 2.20 4.900 length for the application. Go 1.6 exh valve too. Reconsider the short stroke deal unless it's a really long endurance app where you have to be at big rpm for an extended time(boat, desert truck, etc). Chev70elle is right, cam guy will spec the springs, but expect at least 180-200#'s on the seat and probably in the 500's open depending on what the lobe design looks ike. What intake? Low ram? Hi Ram? ITB?
Cam is 235/242 .621/.592 111+3, should give me the mid/top I need , on 1.8 rockers it should be .657/.627 lift
And yeah, it’s a short stroke setup on purpose—keeps piston speed down and lets it live at higher RPM. I’ll trade some torque off the corner for that reliability
Thread Starter
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I’d like to know what intake as well, and what size TB’s. Also wonder who’s working the LS3 heads for this project. I’ve seen several guys both here on Tech, and on another site attempt to build a setup just like this, with the LS platform. You really need to move the lifters in the block to do this reliably, as you’ll need a big pushrod. An .850” diameter lifter wheel will help with camshaft lobe profile a ton, which means a .937” lifter body. Jesel makes them, as does LSM, Xceldyne, and Morel. Takes a lot of airflow to go 9k+ rpm. We did it in the cup world in the 90’s, (flat tappet lifters to boot) so it’s not anything new, you just have to cross your t’s and dot your i’s or you’ll end up with a dyno room full of shrapnel and oil everywhere. The jump from 8k rpm to 9k rpm is a huge step in innovation and financial commitment.
During the early phase the engine won’t be spun past low to mid 8k rpm, but once everything’s proven I’ll start pushing higher. That way I can shake it down without turning the dyno room into a parts shower.
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Did you see the SBE LS3 Eric Roycroft built? I got some details out of him, but he admitted to Hyd roller, ported Low ram w/ dual carbs, ported stock heads, stock rockers, .625 lift cam. Would not admit duration, but had a mild split( my guess is something like a 260/268 110lsa ish). Made 735fwhp at over 8000rpm and was still climbing but ran out of valve spring. No details on bottom end so not sure how "SBE" it was.
Thanks man, solid input. This one’s built for time attack so I’m more worried about staying alive at RPM than chasing a dyno number. Running a Low Ram with a Nick Williams 102, and stuck with Ferrea hollow-stem stock valves for endurance—trying to keep guides and seats happy over long sessions.
Cam is 235/242 .621/.592 111+3, should give me the mid/top I need , on 1.8 rockers it should be .657/.627 lift
And yeah, it’s a short stroke setup on purpose—keeps piston speed down and lets it live at higher RPM. I’ll trade some torque off the corner for that reliability
Cam is 235/242 .621/.592 111+3, should give me the mid/top I need , on 1.8 rockers it should be .657/.627 lift
And yeah, it’s a short stroke setup on purpose—keeps piston speed down and lets it live at higher RPM. I’ll trade some torque off the corner for that reliability