Stainless steel exhaust valves on ls7
01-20-2019, 01:38 PM
#1
Stainless steel exhaust valves on ls7
I’ve noticed that lots of shops replace the sodium filled exhaust valves on the ls7 with stainless steel valves which are heavier.
katech did some research here:
http://www.superchevy.com/how-to/140...#ixzz3Ce45USBo
that suggests that the stainless steel valves resulted in more valve train bounce than the stock sodium filled valves. They also mentioned that they didn’t find anything wrong with the stock valves.
so why do so many shops replace the stock valves with stainless steel??
katech did some research here:
http://www.superchevy.com/how-to/140...#ixzz3Ce45USBo
that suggests that the stainless steel valves resulted in more valve train bounce than the stock sodium filled valves. They also mentioned that they didn’t find anything wrong with the stock valves.
so why do so many shops replace the stock valves with stainless steel??
01-20-2019, 07:48 PM
#2
Problem is the sodium valves and the vavle guides wear, causing slop between the two, and when the valves go to close, they may not be seating squarely with the seats when they seat. So with the sodium valves, this can cause the valve heads to snap off from the unsquare seatting, and sending the valve head into the cylinders.
Also, some of the LS7's came with valve guides out of spec, so it was not even a wear problem on some of the motors that where snapping valve heads off to take out the motor.
So the SS valves tend to hold up longer, isntead of snapping a head off when the guide to valve stems wears cause excess slop between them.
So its not that the SS valves are better, it just that tend to last longer/less chance of them snapping off the valve heads to take a motor out isntead.
Also, some of the LS7's came with valve guides out of spec, so it was not even a wear problem on some of the motors that where snapping valve heads off to take out the motor.
So the SS valves tend to hold up longer, isntead of snapping a head off when the guide to valve stems wears cause excess slop between them.
So its not that the SS valves are better, it just that tend to last longer/less chance of them snapping off the valve heads to take a motor out isntead.
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Eli-Z06 (01-18-2023)
01-21-2019, 03:16 PM
#3
Team Owner
Knee jerk reaction to a symptom of a larger problem that went incorrectly diagnosed several years back. There really isn't a need to run solid SS ex valves in the LS7. Aside from the early (2006 to somewhere in 2008) Part # OE ex valves that had uneven wall thickness, and uneven amounts of sodium fill; there's really nothing wrong with the current Part # OE exhaust valves. It's the go-to exhaust valve in most Katech builds, unless the customer wants to spring for Ti exhaust valves. Are there better (quality) choices out there, sure...one such example is the Ferrea F2042p which is a 1-piece design hollow stem valve that is slightly heavier than OE, but much lighter than a solid stem SS valve. That slight increase in mass can very easily be offset by running a better than OE spring and lightweight retainer, like the PSI 1511's w/ Ti retainers combo (provided the 1511's are the proper spring for your build).
01-21-2019, 11:48 PM
#4
So why does American heritage performance offer the ferrea hollow stem valves in their heads package without upgraded springs? Like their default heads package includes ferrea hollow stem valves and the stock springs. I suppose they have thought about this but wouldn’t the increased mass be a problem if they don’t use aftermarket springs to compensate? Or do they compensate for it in some other way?
01-22-2019, 01:26 AM
#5
Team Owner
So why does American heritage performance offer the ferrea hollow stem valves in their heads package without upgraded springs? Like their default heads package includes ferrea hollow stem valves and the stock springs. I suppose they have thought about this but wouldn’t the increased mass be a problem if they don’t use aftermarket springs to compensate? Or do they compensate for it in some other way?