Notching pistons for comp 270's???
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Stan Weiss
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Do you understand what degreeing in a cam does? You are making sure that you installed the cam correctly, the manufacture made the cam correctly, and if needed you changed its centerline correctly. Are you installing the cam and springs on the heads or is the head porter and who will do all the needed checking there? You do know that advancing the cam gives more exhaust clearance and less intake clearance and retarding gives less exhaust clearance and more intake clearance. The easy way to get more on both without cutting the pistons is a thicker head gasket but that lowers your CR. When all is said and done the best think to do is cut the pistons. I do not know if you can do it on the 281 but ISKY made a tool which let you cut the pistons while still in the block.
LaserRed01GT
Banned
Yes, you can cut the pistons while they are still in the block. Isky does make a tool to to do this, but I have used the Lindy cutter and I liked it better than the Isky.
http://www.lindytools.com/index.html
Now I have cut other BBC and BBF pistons using this "in-head" process and it works very well. But, these mod motors use a valve that has a much smaller valve stem diameter than that of a tradition pushrod motor. Most pushrod motors use a 5/16" or 11/32" stem diameter. Our 2 valve 4.6's have a .2746"-.2754" intake valve stem diameter, and the exhaust valve stem diameter will range from .2736" - .2744". You might have a hard time finding the appropriate guide rod diameter to use with the cutting head. I would call Lindy Tools and/or Isky and see if they make the appropriate guide rods for our heads.
When you re-install the valves after cutting the pistons, be sure to check the valve stem to guide clearances, it’s very important.
Valve Stem to guide clearance:
Intake 0.00078"-0.00272"
Exhaust 0.0018"-0.0037"
http://www.lindytools.com/index.html
Now I have cut other BBC and BBF pistons using this "in-head" process and it works very well. But, these mod motors use a valve that has a much smaller valve stem diameter than that of a tradition pushrod motor. Most pushrod motors use a 5/16" or 11/32" stem diameter. Our 2 valve 4.6's have a .2746"-.2754" intake valve stem diameter, and the exhaust valve stem diameter will range from .2736" - .2744". You might have a hard time finding the appropriate guide rod diameter to use with the cutting head. I would call Lindy Tools and/or Isky and see if they make the appropriate guide rods for our heads.
When you re-install the valves after cutting the pistons, be sure to check the valve stem to guide clearances, it’s very important.
Valve Stem to guide clearance:
Intake 0.00078"-0.00272"
Exhaust 0.0018"-0.0037"
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