Flycutting?
Safety Car
Joined: Jun 2004
Posts: 3,563
Likes: 2
From: Dallas Tx
It's cutting material out of the tops of the pistons, generally to allow for valve clearance or to reduce a dome to reduce compresson. Price will vary by machine shop. Normally if you get the right piston, head, cam... combo, shouldn't need to be machining on the pistons.
Tech Contributor
Joined: Mar 2003
Posts: 12,094
Likes: 197
From: Colorado Springs, CO
St. Jude Donor '08-'09-'10-'11
The vast majority if not all people needing this done arent going to disassemble thier engine to have a machine shop do it with free pistons. Cartek does this routinly fro most of their H/C jobs and all of the 3x cams installs with 4x heads.
None of todays bigger cams fit without flycutting, if you use the optimum compression, and nothing over a 224 cam will fit with LS3 heads milled for proper compression.
Fly cutting is done with the engine assembled in the car with the heads removed. A head of the type you use is rented. The rented head has an isky fly-cut bit that replaces the intake valve. You cant use a 243 head for the cutting if you use a LS3 head on the motor since the valves arent in the same locations. The cutter fits because the valve seats are removed. The head is placed on the engine with the piston you are fly-cutting at the top postion but not negative deck height. The cutter is lowered to the piston and a small guide bearing is attached to limit the depth of the cut. The adjustment is with a feeler guage attached to the stem out the top of the head and adjusted to the depth you want and the bearing is locked in that postion. The cutter is oversized to the size of the valve and the interferance of the valve/piston clearance isnt at TDC. For this reason the cutter is oversized and the added clearance will be slightly less than the full cut, so go over by a little. If you need +.050 then cut in .070. The max for flycutting is another topic for debate but .100 has beed done but I would go that deep on a N2O application. For reference the piston is .220 thick. Also the L92/LS3 heads are closer to the cylinder walls and therefore closer to the ring lands. Anything above .070 on pistons using a LS3 heads as a cutter head is asking for trouble as you will compromise the strength of a piston being that close.
You spin the cutter with a drill, a right angle drill for the back ones). When the bearing touches the valve guide you remove the head and there will be a notch. The cutter goes to the next position and the shavings are cleaned up. Tape up and do the next piston.
There is no side effect for .070". It is less than 1cc. Balance is an issue but GM already messed that up by having a 70grm tolerance as what they call balanced. Ask a machine shop what they consider balanced and sit back and laugh it off.
I am doing a full thread on how to do this with pictures shortly since I am doing it again it that time.
I will have a ton of pics alone with proceedures for handling the aluminum shavings, how to mask the engine, and proper measuring of the volume for the valve relief in calculating the new static compression...and the new dynamic compression if anyone needs to know how to find it.
None of todays bigger cams fit without flycutting, if you use the optimum compression, and nothing over a 224 cam will fit with LS3 heads milled for proper compression.
Fly cutting is done with the engine assembled in the car with the heads removed. A head of the type you use is rented. The rented head has an isky fly-cut bit that replaces the intake valve. You cant use a 243 head for the cutting if you use a LS3 head on the motor since the valves arent in the same locations. The cutter fits because the valve seats are removed. The head is placed on the engine with the piston you are fly-cutting at the top postion but not negative deck height. The cutter is lowered to the piston and a small guide bearing is attached to limit the depth of the cut. The adjustment is with a feeler guage attached to the stem out the top of the head and adjusted to the depth you want and the bearing is locked in that postion. The cutter is oversized to the size of the valve and the interferance of the valve/piston clearance isnt at TDC. For this reason the cutter is oversized and the added clearance will be slightly less than the full cut, so go over by a little. If you need +.050 then cut in .070. The max for flycutting is another topic for debate but .100 has beed done but I would go that deep on a N2O application. For reference the piston is .220 thick. Also the L92/LS3 heads are closer to the cylinder walls and therefore closer to the ring lands. Anything above .070 on pistons using a LS3 heads as a cutter head is asking for trouble as you will compromise the strength of a piston being that close.
You spin the cutter with a drill, a right angle drill for the back ones). When the bearing touches the valve guide you remove the head and there will be a notch. The cutter goes to the next position and the shavings are cleaned up. Tape up and do the next piston.
There is no side effect for .070". It is less than 1cc. Balance is an issue but GM already messed that up by having a 70grm tolerance as what they call balanced. Ask a machine shop what they consider balanced and sit back and laugh it off.
I am doing a full thread on how to do this with pictures shortly since I am doing it again it that time.
I will have a ton of pics alone with proceedures for handling the aluminum shavings, how to mask the engine, and proper measuring of the volume for the valve relief in calculating the new static compression...and the new dynamic compression if anyone needs to know how to find it.
Thread Starter
Racer
Joined: Jan 2008
Posts: 285
Likes: 0
From: Boca raton Florida
The vast majority if not all people needing this done arent going to disassemble thier engine to have a machine shop do it with free pistons. Cartek does this routinly fro most of their H/C jobs and all of the 3x cams installs with 4x heads.
None of todays bigger cams fit without flycutting, if you use the optimum compression, and nothing over a 224 cam will fit with LS3 heads milled for proper compression.
Fly cutting is done with the engine assembled in the car with the heads removed. A head of the type you use is rented. The rented head has an isky fly-cut bit that replaces the intake valve. You cant use a 243 head for the cutting if you use a LS3 head on the motor since the valves arent in the same locations. The cutter fits because the valve seats are removed. The head is placed on the engine with the piston you are fly-cutting at the top postion but not negative deck height. The cutter is lowered to the piston and a small guide bearing is attached to limit the depth of the cut. The adjustment is with a feeler guage attached to the stem out the top of the head and adjusted to the depth you want and the bearing is locked in that postion. The cutter is oversized to the size of the valve and the interferance of the valve/piston clearance isnt at TDC. For this reason the cutter is oversized and the added clearance will be slightly less than the full cut, so go over by a little. If you need +.050 then cut in .070. The max for flycutting is another topic for debate but .100 has beed done but I would go that deep on a N2O application. For reference the piston is .220 thick. Also the L92/LS3 heads are closer to the cylinder walls and therefore closer to the ring lands. Anything above .070 on pistons using a LS3 heads as a cutter head is asking for trouble as you will compromise the strength of a piston being that close.
You spin the cutter with a drill, a right angle drill for the back ones). When the bearing touches the valve guide you remove the head and there will be a notch. The cutter goes to the next position and the shavings are cleaned up. Tape up and do the next piston.
There is no side effect for .070". It is less than 1cc. Balance is an issue but GM already messed that up by having a 70grm tolerance as what they call balanced. Ask a machine shop what they consider balanced and sit back and laugh it off.
I am doing a full thread on how to do this with pictures shortly since I am doing it again it that time.
I will have a ton of pics alone with proceedures for handling the aluminum shavings, how to mask the engine, and proper measuring of the volume for the valve relief in calculating the new static compression...and the new dynamic compression if anyone needs to know how to find it.
None of todays bigger cams fit without flycutting, if you use the optimum compression, and nothing over a 224 cam will fit with LS3 heads milled for proper compression.
Fly cutting is done with the engine assembled in the car with the heads removed. A head of the type you use is rented. The rented head has an isky fly-cut bit that replaces the intake valve. You cant use a 243 head for the cutting if you use a LS3 head on the motor since the valves arent in the same locations. The cutter fits because the valve seats are removed. The head is placed on the engine with the piston you are fly-cutting at the top postion but not negative deck height. The cutter is lowered to the piston and a small guide bearing is attached to limit the depth of the cut. The adjustment is with a feeler guage attached to the stem out the top of the head and adjusted to the depth you want and the bearing is locked in that postion. The cutter is oversized to the size of the valve and the interferance of the valve/piston clearance isnt at TDC. For this reason the cutter is oversized and the added clearance will be slightly less than the full cut, so go over by a little. If you need +.050 then cut in .070. The max for flycutting is another topic for debate but .100 has beed done but I would go that deep on a N2O application. For reference the piston is .220 thick. Also the L92/LS3 heads are closer to the cylinder walls and therefore closer to the ring lands. Anything above .070 on pistons using a LS3 heads as a cutter head is asking for trouble as you will compromise the strength of a piston being that close.
You spin the cutter with a drill, a right angle drill for the back ones). When the bearing touches the valve guide you remove the head and there will be a notch. The cutter goes to the next position and the shavings are cleaned up. Tape up and do the next piston.
There is no side effect for .070". It is less than 1cc. Balance is an issue but GM already messed that up by having a 70grm tolerance as what they call balanced. Ask a machine shop what they consider balanced and sit back and laugh it off.
I am doing a full thread on how to do this with pictures shortly since I am doing it again it that time.
I will have a ton of pics alone with proceedures for handling the aluminum shavings, how to mask the engine, and proper measuring of the volume for the valve relief in calculating the new static compression...and the new dynamic compression if anyone needs to know how to find it.
