A note on valve springs.
Thread Starter
Supporting Vendor
Joined: Jul 2010
Posts: 8,550
Likes: 903
From: Republic of Texas
A note on valve springs.
For those of you considering a Cam swap or higher-ratio rockers. A commonly overlooked aspect is your valve springs. About a year go, I swapped out my stock rockers for a set of Yella Terra 1.8 rockers. The extra lift acted like a small cam but without the extra labor and parts cost. A trip to the dyno revealed valve float around 5000 rpm.
For those that don't know, valve float is an adverse condition which occurs when the poppet valves on an internal combustion engine valvetrain do not remain in contact with the camshaft lobe during the valve closure phase of the cam lobe profile. This reduces engine efficiency and performance and potentially increases engine emissions.
For my N/A setup, I didn’t make a big deal of it and left the car on stock springs for about a year. However when moving to my FI setup this year, I opted to install new valve springs since valve float becomes a major issue under FI applications.
For my application, I went with PAC 1218 springs from SDPC (they had the lowest price I found) The Pac 1218 can re-use the OEM mounting components. I shot a few comparison pics of the stock LS1 springs vs the new ones. You can see both width and height difference.
One can feel the difference in spring strength simply by squeezing them with your fingers. The new springs are considerably stiffer and their additional height makes them perfect for larger rocker applications.
For those that don't know, valve float is an adverse condition which occurs when the poppet valves on an internal combustion engine valvetrain do not remain in contact with the camshaft lobe during the valve closure phase of the cam lobe profile. This reduces engine efficiency and performance and potentially increases engine emissions.
For my N/A setup, I didn’t make a big deal of it and left the car on stock springs for about a year. However when moving to my FI setup this year, I opted to install new valve springs since valve float becomes a major issue under FI applications.
For my application, I went with PAC 1218 springs from SDPC (they had the lowest price I found) The Pac 1218 can re-use the OEM mounting components. I shot a few comparison pics of the stock LS1 springs vs the new ones. You can see both width and height difference.
One can feel the difference in spring strength simply by squeezing them with your fingers. The new springs are considerably stiffer and their additional height makes them perfect for larger rocker applications.
Le Mans Master
Joined: May 2007
Posts: 5,393
Likes: 17
From: Belleville Mich.
When you switched to the Yella Terra 1.8 rockers, is that the only change you made? You didn't change the push rods?
Will those rockers slide in without changing out any thing eles?(such as push rods?)
I switched to new springs last week and kept my stock rockers (Z06 LS6)
Will those rockers slide in without changing out any thing eles?(such as push rods?)
I switched to new springs last week and kept my stock rockers (Z06 LS6)
Thread Starter
Supporting Vendor
Joined: Jul 2010
Posts: 8,550
Likes: 903
From: Republic of Texas
When you switched to the Yella Terra 1.8 rockers, is that the only change you made? You didn't change the push rods?
Will those rockers slide in without changing out any thing eles?(such as push rods?)
I switched to new springs last week and kept my stock rockers (Z06 LS6)
Will those rockers slide in without changing out any thing eles?(such as push rods?)
I switched to new springs last week and kept my stock rockers (Z06 LS6)
Rockers are bolt on with no special modifications required for your application. 97-98 LS1s with peremited bolt valve covers may require a 1/2" valve cover spacer for clearancing.
Thread Starter
Supporting Vendor
Joined: Jul 2010
Posts: 8,550
Likes: 903
From: Republic of Texas
Not sure why rockers aren't used as much. 1.8 or larger rockers act like a multiplier to the cam lobes. Lift is magnified and duration remains the same. Since duration and LSA remain the same, driving characteristics are maintained and the only difference is more power.
Safety Car
Joined: Jun 2009
Posts: 3,888
Likes: 2
From: Frederick, Maryland
Not sure why rockers aren't used as much. 1.8 or larger rockers act like a multiplier to the cam lobes. Lift is magnified and duration remains the same. Since duration and LSA remain the same, driving characteristics are maintained and the only difference is more power.
Do you think the reason you got valve float is because you changed the rockers? How big did you know to go without interfering with the cam? Such as having to flycut the pistons if that can happen. I faintly remember some similarity of having too big of a lift or something...
