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918 Valve Spring Question

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Old 01-05-2007, 09:38 AM
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Default 918 Valve Spring Question

I have been doing some looking and the 918s are rated at different specs at a few different places. JRP rates them to 625 lift and sponsors rate them to 600 lift. What size cams are you guys running with 918s and not having any problems. Im considering to upgrading cams to a 600 609 and was wondering if I needed to go ahead and change the springs. Any info is appreciated.

Brian
Old 01-05-2007, 09:46 AM
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If you are running 918's and wish to swap cams to those lifts, you'll have to change springs to new ones anyways. You can run 918s again or go to duals like PP/PRC golds.

The 918's WILL handle those lifts if properly setup.
Old 01-05-2007, 10:22 AM
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how would they need to be properly setup to handle the new lifts?
Old 01-05-2007, 10:46 AM
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Originally Posted by BrianC98Z28
how would they need to be properly setup to handle the new lifts?
1.800" installed spring height for each spring, is a start. I ran on a LT1 a cam with 0.605" intake/exhaust, no issues
Old 01-05-2007, 11:17 AM
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Originally Posted by BrianC98Z28
how would they need to be properly setup to handle the new lifts?
Shimming
Old 01-05-2007, 11:27 AM
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how do you know when you need to shim a spring?
i'll be running my 918 springs with a cam that lifts .575/.563
Old 01-05-2007, 11:30 AM
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Originally Posted by 2000TransAmWS6
how do you know when you need to shim a spring?
i'll be running my 918 springs with a cam that lifts .575/.563
with that lift you dont need to shim anything. with my current cam thats 573 571 we didnt shim anything just installed the springs with stock retainers and its seen 6700 no problem.
Old 01-05-2007, 11:32 AM
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Originally Posted by 2000TransAmWS6
how do you know when you need to shim a spring?
i'll be running my 918 springs with a cam that lifts .575/.563
When the cams pressure requirements exceed or are to close to actual spring pressures.
Old 01-05-2007, 11:45 AM
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Alos its is often recommented not to shim beyond 0.040" if you have to shim more then that to get the proper installed height then that spring is inadequte or there is something wrong with the set up. Now I have heard of locks that are offset to also help getting the recommended height without shimming, I have no exp there but thats just what I heard.

As for Brian's second question, with the 918, it seems to have enough room where the spring wont coil bind. The lift is not near the max recommended lift. I am sure there is some variation in the installed height from spring to spring but its probably not enough to have a negative impact.
Old 01-05-2007, 02:19 PM
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Originally Posted by PREDATOR-Z
When the cams pressure requirements exceed or are to close to actual spring pressures.
thanks for the response!




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