Hollow vs. solid stem valves
Hollow vs. solid stem valves Since the 468 thread was closed right when it was going back technical, we might as well continue here. Those that build big $$$ NA motors and have to pay attention to details for max power when racing etc. Why hollow vs. solid stem valves? I understand it reduces weight, but are there examples showing it gained XX power or extended the RPM range XXX? It seems like the juice isn't worth the squeeze so learn me!
TECH Senior Member
Joined: Jun 2016
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From: Central Cal.
You and I feel it's not worth the risk.. Some do, and when something goes south due to that weaker design, blame gets tossed around. Not the mfr's fault, nor the vendor's.
Racing breaks parts. Hence no warranty. Eat it and move on, WITHOUT tossing blame.
Racing breaks parts. Hence no warranty. Eat it and move on, WITHOUT tossing blame.
TECH Apprentice
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It is true stuff can break. But when your using 800 lb springs and a hollow stem cause that's what the builder said than that's a on the builder.
TECH Senior Member
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From: Central Cal.
OK I get that. In that case the valve mfr is liable here.
The engine builder has used tons of these valves without mishap, so did not see this coming.
The valve broke, causing associated damage.
Mfr. should replace the valve and cover collateral damage, as SOMETHING was wrong with that particular valve, whether the defect was in the materials, welding, or other process.
My opinion....
The engine builder has used tons of these valves without mishap, so did not see this coming.
The valve broke, causing associated damage.
Mfr. should replace the valve and cover collateral damage, as SOMETHING was wrong with that particular valve, whether the defect was in the materials, welding, or other process.
My opinion....
I don't want to get this locked so let's not focus on whose to blame in the event of a failure. I want to understand the benefits and why they're used on anything but an absolute max effort. If hollow stems are more prone to fail, even if the failures are few and far between, why use them at all if there isn't much benefit?
TECH Senior Member
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From: Central Cal.
I think that depends on the risk one wants to assume.
Some will risk breakage (and ruined engine) to get that last bit of power, while others (me, and I think many others) feel it isn't worth it.
All in what you want, or are willing to risk. But don't cry when it breaks....
Some will risk breakage (and ruined engine) to get that last bit of power, while others (me, and I think many others) feel it isn't worth it.
All in what you want, or are willing to risk. But don't cry when it breaks....
I think that depends on the risk one wants to assume.
Some will risk breakage (and ruined engine) to get that last bit of power, while others (me, and I think many others) feel it isn't worth it.
All in what you want, or are willing to risk. But don't cry when it breaks....
Some will risk breakage (and ruined engine) to get that last bit of power, while others (me, and I think many others) feel it isn't worth it.
All in what you want, or are willing to risk. But don't cry when it breaks....
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TECH Junkie
Joined: May 2012
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From: Poplarville, MS
Why not just run a little more spring pressure to make up for the weight of the valve? In a max effort build one would be using a sold lifter anyway, so over powering the lifter would not be an issue.
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All the talk about light rockers and valves is good and all and those do help to rev the motor faster but when it's all said and done it is really the valve springs job to keep the valve from floating and once that happens whether it be by an ineffective spring or insufficient guide clearance the end result can lead to a valve kissing a piston followed by a snapped valve and then more carnage. I don't care if they're hollow stems, solid stainless or even titanium valves because they all can all float and eventually snap off. It's just the price we pay when building racing engines.
On The Tree
Joined: Jun 2019
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From: HTown, Texas
I don't want to get this locked so let's not focus on whose to blame in the event of a failure. I want to understand the benefits and why they're used on anything but an absolute max effort. If hollow stems are more prone to fail, even if the failures are few and far between, why use them at all if there isn't much benefit?
A lighter valve can help you in a number of way depending on your objective. For for the sake of reliability, it means that you don't need as much spring pressure for a given RPM and cam profile, so you can run a spring with a lower rate, which are typically less brittle, have longer service life, and will generate less heat.
If your objective is more power, then you can keep the higher rate spring and turn more RPM, which will make more power with the right cam and heads. Or instead, you can just use a more aggressive cam and make more power within the lower RPM range.
Keep in mind that GM used the hollow stem valves in factory LS6 and LS3 engines, so I don't think there is much of a reliability concern when they are manufactured and used correctly, Poorly manufactured solid stem valve will fail as well.
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From: Central Cal.
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Asked something Similar on YB was told basically what Camaro Said...
Doesn't matter which valve as long as it's in control with the Best Springs available
Conversation was about a 6.2 length solid stem valve vs a titanium one going to 7800. What head was this for?
C5r- DR/CT heads and trying to find a cheaper route than a titanium valve.
It worked out on paper...
Key was and is the Springs keeping the valve in control.
Doesn't matter which valve as long as it's in control with the Best Springs available
Conversation was about a 6.2 length solid stem valve vs a titanium one going to 7800. What head was this for?
C5r- DR/CT heads and trying to find a cheaper route than a titanium valve.
It worked out on paper...
Key was and is the Springs keeping the valve in control.
There are many benefits to reducing the valvetrain weight, especially on the valve side of the rocker arm. Simply understanding that force equal mass times acceleration should be enough proof.
A lighter valve can help you in a number of way depending on your objective. For for the sake of reliability, it means that you don't need as much spring pressure for a given RPM and cam profile, so you can run a spring with a lower rate, which are typically less brittle, have longer service life, and will generate less heat.
If your objective is more power, then you can keep the higher rate spring and turn more RPM, which will make more power with the right cam and heads. Or instead, you can just use a more aggressive cam and make more power within the lower RPM range.
Keep in mind that GM used the hollow stem valves in factory LS6 and LS3 engines, so I don't think there is much of a reliability concern when they are manufactured and used correctly, Poorly manufactured solid stem valve will fail as well.
A lighter valve can help you in a number of way depending on your objective. For for the sake of reliability, it means that you don't need as much spring pressure for a given RPM and cam profile, so you can run a spring with a lower rate, which are typically less brittle, have longer service life, and will generate less heat.
If your objective is more power, then you can keep the higher rate spring and turn more RPM, which will make more power with the right cam and heads. Or instead, you can just use a more aggressive cam and make more power within the lower RPM range.
Keep in mind that GM used the hollow stem valves in factory LS6 and LS3 engines, so I don't think there is much of a reliability concern when they are manufactured and used correctly, Poorly manufactured solid stem valve will fail as well.
TECH Resident
Joined: Sep 2019
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From: Melbourne, Australia
If i swapped from the solids im using now to a hollow or titanium, without changing cams , there would be absolutely no power gain. The gain i would make is longevity by being able to use lighter spring pressures which in turn will put less stress on lifter wheels, rocker arms. Valve springs aren't infinite, they have a life span, the more pressure the more wear , on the springs themselves, rocker arms, lifters, the valves themselves..
If i used a hollow or titanium, changed to a bigger cam, more lift, yes id make power but would be going back to square one with longevity of parts..... viscious circle.....
New parts will and do break, **** happens and putting blame on anyone other than the manufacturer is plain n simple just dumb, unless used outside of the parameters of said part which a supplier has recommended......
If i used a hollow or titanium, changed to a bigger cam, more lift, yes id make power but would be going back to square one with longevity of parts..... viscious circle.....
New parts will and do break, **** happens and putting blame on anyone other than the manufacturer is plain n simple just dumb, unless used outside of the parameters of said part which a supplier has recommended......
Is valve spring life really something being considered on a street car when someone is dropping 10s of thousands of dollars? Does 10k mile spring changes vs 15k mile changes matter?