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| longer vales vs gross valve lift https://slantsix.org/forum/viewtopic.php?t=34971 |
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| Author: | pmarvetz [ Mon Apr 20, 2009 10:57 pm ] |
| Post subject: | longer vales vs gross valve lift |
Have any of you guy's using longer valves checked your gross valve lift before and after installing the longer valves? it seems as though I have lost .030 of lift after going to the longer valves. Anyone else have this problem? Will shimming the shaft cure it? |
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| Author: | Rug_Trucker [ Wed Apr 22, 2009 9:04 am ] |
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| Author: | sandy in BC [ Wed Apr 22, 2009 9:29 am ] |
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I have longer V/vs (.100) sbc I had to use shorter pushrods after I milled 140 for compression but the valve angles at under .500 lift were acceptable. With only .040 off the deck and >500 lift I was nearly out of rocker adjustment and had to use locknuts. I can see the geometry change but I am surprised at that much lift loss. Shimming the shaft is ugly. How long are your valves? What is your lift? How does the rocker look on the valve tip at .500 lift? |
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| Author: | Dart270 [ Wed Apr 22, 2009 9:38 am ] |
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I am surprised by that much difference too. I've never done a back-to-back comparison. Lou |
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| Author: | slantzilla [ Wed Apr 22, 2009 5:14 pm ] |
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I would venture to guess that the difference comes from loss of rocker geometry/ratio. 
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| Author: | pmarvetz [ Wed Apr 22, 2009 11:02 pm ] |
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Does anyone make 1.6 ratio rockers? I thought I saw some on ebay awhile back. |
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| Author: | 66aCUDA [ Thu Apr 23, 2009 4:54 am ] |
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RAS in Northern Ca or Cox Brothers in Columbus,OH Frank |
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| Author: | dakight [ Thu Apr 23, 2009 4:59 am ] |
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the rocker arm tip moves through an arc. Near the ends of the arc the motion is more lateral and less vertical. It should be possible to compute the difference but I agree that .030 seems a bit much. |
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| Author: | ceej [ Thu Apr 23, 2009 7:52 am ] |
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The rocker tip also slides a short distance on the top of the valve. The curved surface may be starting out with a dimension that allows you to set the clearance, but with a greater angle to the top of the valve stem, as the rocker's curved surface slides along the top of the valve stem, the geometry of the whole system changes. If there is excessive wear to the rocker where it was running before, you could be "Loosening up" as the tip sweeps across into the wear area. Check your rockers out for wear. Pull the valves and shorten the stems up to correct the geometry, or shim the shaft. 2¢ CJ |
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| Author: | Rug_Trucker [ Thu Apr 23, 2009 8:10 am ] |
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This could actually go into math that would make my head hurt 
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| Author: | pmarvetz [ Thu Apr 23, 2009 8:44 am ] |
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I'm checking the lift with the rockers at 0 lash. I used to have .415 on the intake and.400 on the exhaust now I have .370 and .380.BTW I need a non roller type rocker. |
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| Author: | Dart270 [ Thu Apr 23, 2009 10:35 am ] |
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There can also supposedly be pretty big differences in rocker ratio for the factory ones, from others who have measured this. I have not. Could be the specific rockers you are using to measure. Lou |
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| Author: | slantzilla [ Thu Apr 23, 2009 2:34 pm ] |
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Clifford supposedly has 1.6 rockers now that are not roller. Someone on here actually got a set, and they looked decent. They are very salty though, about equal a set of rollers.
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| Author: | pmarvetz [ Thu Apr 23, 2009 8:26 pm ] |
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I knew I had seen them somewhere. I have a set ordered, Thanks for the reminder. |
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