918 springs good for .600 lift on street
03-07-2006, 10:00 PM
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918 springs good for .600 lift on street I talked to Research & Development guy at Comp Cam today and he said a 918 springs were good for .650 lift if you were using the car at the race track only. .600 lift if it were a street car. In other words .650 lift for a short time and .600 lift for a long time, checking them periodically ( 8 to 10 thousand miles) for a street car. He also said the new wire is strong and pure (no porosity or voids) and that there is no comparison to the wire of a few years ago. Todays 918 springs are Superior.
03-07-2006, 10:16 PM
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I know some that have been on the street for a year with .630" lift.
The install height is a bit more than stock because no need for excess seat pressure with the light Z06 valves.
The closer you are running them to bind, the shorter the life,
so it all depends on where you set the install height.
The install height is a bit more than stock because no need for excess seat pressure with the light Z06 valves.
The closer you are running them to bind, the shorter the life,
so it all depends on where you set the install height.
03-08-2006, 02:01 AM
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I've been told by Thunder that the 918's are just fine @ .600 lift. Everybody here will try to scare you, but they'll be okay.
The dollar value you want to put on security is a personal choice. When in doubt, go safe for a few more bucks and get the duels.
Good luck to you!!
The dollar value you want to put on security is a personal choice. When in doubt, go safe for a few more bucks and get the duels.
Good luck to you!!
03-09-2006, 03:06 PM
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I've had the spring pockets machined down by .080" and then shimmed.
without the machining, adding shims just reduces the install height and makes the problem worse.
without the machining, adding shims just reduces the install height and makes the problem worse.
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03-09-2006, 03:13 PM
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Originally Posted by CaptUSA
I've been told by Thunder that the 918's are just fine @ .600 lift. Everybody here will try to scare you, but they'll be okay.
The dollar value you want to put on security is a personal choice. When in doubt, go safe for a few more bucks and get the duels.
Good luck to you!!
The dollar value you want to put on security is a personal choice. When in doubt, go safe for a few more bucks and get the duels.
Good luck to you!!
I went with 921s just to be safe. If a dual breaks, hopefuly you can get home. Dave
03-09-2006, 06:29 PM
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Originally Posted by ChiefDave
I went with 921s just to be safe. If a dual breaks, hopefuly you can get home. Dave
03-09-2006, 06:33 PM
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Set them up for the recommended install height and you will be fine. I ran 918s for 60,000 miles set at stock install height with a baby 218/224 .561/.567 comp cam....They are VERY well made springs.
With my Z06 and current 228 .588 lift XER lobe I broke an ISKY single after approx 20,000 miles.
I just felt a little better going with the strongest street spring possible so I went with the PRC duals on my new heads...same cam. Overkill? Probably... The 918s would have probably been fine, after all I had already got 20,000 miles out of the Isky singles...
With my Z06 and current 228 .588 lift XER lobe I broke an ISKY single after approx 20,000 miles.
I just felt a little better going with the strongest street spring possible so I went with the PRC duals on my new heads...same cam. Overkill? Probably... The 918s would have probably been fine, after all I had already got 20,000 miles out of the Isky singles...
03-09-2006, 09:17 PM
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Originally Posted by PREDATOR-Z
I usualy start shimming them after .590 lifts as far as .050 from coilbind if necessary
03-09-2006, 09:53 PM
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Originally Posted by dug
Does shimming the springs for more preload affect lifespan?
FYI, you shim rockers for less preload at the lifter.
03-09-2006, 10:28 PM
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Originally Posted by white2001s10
You don't shim springs for pre-load, you shim springs for seat pressure. More seat pressure = less lifespan.
FYI, you shim rockers for less preload at the lifter.
FYI, you shim rockers for less preload at the lifter.
03-10-2006, 11:02 AM
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Originally Posted by white2001s10
You don't shim springs for pre-load, you shim springs for seat pressure. More seat pressure = less lifespan.
FYI, you shim rockers for less preload at the lifter.
FYI, you shim rockers for less preload at the lifter.
You shim for increased seat pressure to handle higher lifts and reduce chances of valve float, but in LSx case, shimming rockers is only needed to center geometry and has little effect on lifter preload.
That is specific to stand non adjustable rockers with hydraulic lifters.
You adjust lifter preload with non adjustable rockers by changing pushrod length.
03-10-2006, 02:53 PM
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Originally Posted by PREDATOR-Z
You shim for increased seat pressure to handle higher lifts and reduce chances of valve float, but in LSx case, shimming rockers is only needed to center geometry and has little effect on lifter preload.
That is specific to stand non adjustable rockers with hydraulic lifters.
You adjust lifter preload with non adjustable rockers by changing pushrod length.
That is specific to stand non adjustable rockers with hydraulic lifters.
You adjust lifter preload with non adjustable rockers by changing pushrod length.
