Increasing valve lift
12-05-2005, 06:45 PM
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Increasing valve lift My camshaft is .558/.558 with the stock 1.72 rocker. I have the Comp-Cams 918 beehive springs and they are supposed to be good for .600 lift. If I change the rockers to a set of 1.85 it will put the lift right at .600/.600. As such I realize that Comp does factor in a little leeway into these calculations but I am still a little skeptical so my questions are as follows - Has anyone else run this close to the limit with LS1 springs? If so was everything OK at the high-6000/low-7000 rpm limit? I realize that the springs are good up to .600 and that the new lift would be .600 and as such they should be good-to-go but I would rather ask around than find out the hard way that I should have went another route as bad stuff happens quickly at 7000-rpm. Thanks in advance for any and all input.
Jim C.
Jim C.
12-06-2005, 06:40 AM
#3
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For starters, going to 1.85 with those cam lifts is not a good idea. The only rockers on the market that I would recommend something like that is the CRANE 1.82 variable lift.
But just to answer your question, i would just shim the 918's to .100 of coilbind and you should be good to go.
But just to answer your question, i would just shim the 918's to .100 of coilbind and you should be good to go.
12-06-2005, 07:19 AM
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Gentleman, thank you for your advice. I guess I will be sticking with the stock rockers then. Just out of curiousity, what is the reasoning behind not using the 1.85's with that particular camshaft? Again, thank you and happy holidays to you and yours.
- That makes two of us !!!
Jim C.
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"I've got enough Summit Racing stickers to wallpaper my house"
Jim C.
12-06-2005, 09:15 AM
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I wish I knew why you shouldn't run 1.85 rockers as well.
A friend of mine with a C5 is running Comp 1.85's with 918 springs for .630" lift & LPE2-3 cam. Spring pockets were cut .090" and .015" shims used. He is using the light weight 2002+ Z06 valves.
As you can see you can run higher lifts if you increase the install height by machining the spring pockets down more. The 918's still have good pressure at higher than stock install heights.
A friend of mine with a C5 is running Comp 1.85's with 918 springs for .630" lift & LPE2-3 cam. Spring pockets were cut .090" and .015" shims used. He is using the light weight 2002+ Z06 valves.
As you can see you can run higher lifts if you increase the install height by machining the spring pockets down more. The 918's still have good pressure at higher than stock install heights.
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12-06-2005, 12:16 PM
#8
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It's not all about lifts, higher rockers also alter the rocker arc of motion which will have negative effects on overall geometry.
It is better then just to get a cam ground with the lifts in mind.
It is better then just to get a cam ground with the lifts in mind.
12-06-2005, 12:24 PM
#9
This whole thing of whether or not to use higher ratio rockers has been hashed and rehashed countless times. I've been running the Crane VHP 1.8 gold rockers on my stock 2002 LS1 cam for 6 months now. They give me about .500 lift on the intake and .513 on the exhaust. Before too long I'll be doing a cam swap to something in the range of .585 lift at the 1.8 ratio and I'll be installing heads with the 2002 light-weight Z06 valves, titanium retainers, and crane dual springs. It'll be fine. I'm not concerned about valve float. It'll be very streetable with lots of torque and decent HP. Actually, I did have a valve float issue with my stock rockers and my stock springs. Right now I have the Crane VHP 1.8's and Manley springs & titanium retainers and there isn't any valve float issue. Of course, I don't go above 6400 RPM's.
