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britegreenVWSB
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Joined: June 13, 2004
Posts: 315
Location: Western Washington State
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 Posted: Sun Jul 01, 2012 10:00 am Post subject: Piston Notching for Valve Clearance: When Is It Needed? |
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I'm assembling a 2276. The deck height is at about .058", combustion chamber cc's about 60. I'm using a SLR XR 302 cam which has a lift at the valve of .529". Should I worry about piston to valve interference with this? Is it really necessary to clay the pistons and check? Thanks.
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mark tucker
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Joined: April 08, 2009
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Location: SHALIMAR ,FLORIDA
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| Posted: Sun Jul 01, 2012 10:03 am Post subject: |
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probably not but it's always a good idea.I would bring that deck down to about .035-.040" unless you using a forced induction.
usualy unless your heads have been milled a good bit your good to go. |
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nsracing 
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Joined: November 16, 2003
Posts: 5451
Location: VIRGINIA
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| Posted: Sun Jul 01, 2012 12:12 pm Post subject: |
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It is ALWAYS part of the build to check valve-to-piston clearance if you are installing larger than stock cam.
You want to find out if the valves are going to hit the pistons during the build and not during the running.
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modok
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Posts: 8629
Location: Colorado Springs
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| Posted: Sun Jul 01, 2012 12:29 pm Post subject: |
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| you could also assemble the thing with light checking springs and turn it over 10 degrees at a time and see how much extra travel the valves have. Just push on them and see if how far they go before they hit the piston. |
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neil68
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| Posted: Mon Jul 02, 2012 4:26 pm Post subject: valve-to-piston clearance |
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It really depends on which heads you're using and whether they've been flycut. I've used 044 and JPM heads, both out-of-the-box and later with flycutting. So far I haven't required any piston notching, even with high lift cams such as Engle FK8, Web 251, 226, 86C and JPM cam.
I would recommend that you clay a piston and make certain that you have 2.5-3.0 mm clearance, as the cam timing could also be a factor (ie. advanced or retarded).
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mark tucker
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Location: SHALIMAR ,FLORIDA
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| Posted: Mon Jul 02, 2012 5:06 pm Post subject: |
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| cam timing is more a factor than lift!!! |
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stealth67vw
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Joined: January 22, 2004
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| Posted: Mon Jul 02, 2012 6:03 pm Post subject: |
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| mark tucker wrote: | | cam timing is more a factor than lift!!! |
X2. Lobe center and advanced or retarded cam timing is a bigger factor than lift.
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Bill271
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Joined: July 06, 2008
Posts: 759
Location: escondido
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| Posted: Mon Jul 02, 2012 6:09 pm Post subject: |
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| X3 if that thing stays open or opens at differant times it will hurt itself |
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[email protected]
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Joined: August 03, 2002
Posts: 7047
Location: Salt Lake City, Utah
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| Posted: Mon Jul 02, 2012 7:08 pm Post subject: |
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you don't even have to think about this until you have a cam over 270 degrees @ .050" (86C, FK87, etc), OR have compression over 11:1.
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