HOW TO "flycut pistons"
05-05-2007, 06:13 PM
#1
HOW TO "flycut pistons" first off, if anyone has questions/comments/better pics by all means post up.
obviously this all needs to be done with max effort to keep the internal passages of the eng. clean. we'll start our instructions with the heads removed.
1- clean and cover everything.
2- find TDC with a dial indicator like so. there is a very slight pause at the top so watch for the needle to stop raising, pause, and start goin back down. watch the gauge carefully to see what the highest # seen is. also, notice how the tool is held in the same angle as the piston raises, and is on the middle of the piston where the wristpin is. if you had it at the 12 or 6 oclock positions, it would not be accurate due to the piston tilting in the bore.
3- tape off the complete block deck to keep the shavings from ending up anywhere else. on a side note, you need to try and get the head (tool) on in a way that the valves end up the same distance away from the block deck as the real head will be to try and best duplicate the correct valve angle. in my case, I milled .033" from my heads and used .040 cometics. so that adds up to the valves being .047" closer to the pistons then stock head/head gasket once its all together. the head I used for the tool was unmilled. so right there its .033" farther away then my new setup will be. so in an attempt to get the valves the same distance away from the piston to get the cut at the proper angle, I used 4 layers of blue tape to tape off the block which was right around .020" (I used a digi. mic, dont remember now if was 3 or 4 layers) and add the .033" more meat on the bottom of the head put me right around the proper placement. so I used 4 layers of tape and no head gasket to mock up the cutter. also you'll notice that I cut a window out of the tape in the middle of the piston where the notches will be. you'll see why in a minute.
4-here's what the "tool" looks like. some junk *** stock head with the int/exh. valve seats removed. the cutter slides up into the head in place of a valve. ::edit:: this is before I cut out the exh. seat.::edit::
5-after you have the block taped, and the window cut, apply some wD40 to the cutter and set the head in place and install 2 OLD head bolts. the bolt will pop right through the tape. just give it a pop with your hand. ligthly torque down the head bolts you just put in that are diag. across the cyl your working on. dont need much here, just tigten them up with a normal 3/8" ratchet good and tight. now, loosen up the lock collar and let the valve sit directly on the piston. the reason you wanted to cut the window out of the tape, is so your cuts are accurate, repeatable, and you know how deep they are. with the cutter sitting directly on the piston, collar loose, insert a feeler gauge between the top of the valve guide and below the locking collar. I cut my intakes to .120" deep. whatever you set this step up as, is how deep your cut will be IF you cut all the way down in the comeing up steps.pic 1 here is setting the cut depth with the feeler gauge's stacked to make up .120" total. pic 2 is how you lock down the collar with a very tiny allen wrench.
6- before you can start cutting, you need to take a measurement of the collar before and after you make the cut. this way, if the collar slips you'll know it. here's how I measured the collar position. note: this measurement was up to a few thousandths diff. from cyl. to cyl, due to the valve guide not being in the exact same placement in the head. so you'll have to measure each one to be sure. this is a small steel machinists ruler. see the top of the valve where it lines up with the 3/32" mark before I cut? and see the gap under the colar since this is before I made the cut?
7-now its finally time to make a cut. I used an air drill. but a keyless chuck would def. come in handy here. drill down slowly untill the collar is touching the valve guide. dont press hard though cause you dont want the collar to slip, ever. once you cut too deep, its done for. you'll be pulling atleast that piston for replacement. you can feel when the cutter is done cause it will freespin.
8-put the vacuum hose in the exh. port to remove the chips and "most" of the alum. dust. also helps to block off the intake port with your other hand to apply more vacuum. when cutting the exh. side (if you have to), put the vac. in the inake port instead to remove the bulk of material.
9-remove the head and then vac. the remaining pile of dust that was in the chamber ontop of the tape. next step is to measure the cut to make sure its as deep as you want it to be. you must clean out the cut though with a towel and parts cleaner. it should end up the depth you want. the corner of the feeler gauge should be flush with the middle of the eyebrow cut.
10- once your satisfied with the depth, then take a piece of sand paper and sand off the sharp edges from the cut. and clean off again with clean towel and parts cleaner. you can skip this step if your goin to cut the exh. side too, and sand/clean them both at the same time after you repeat all this for the exh. valve cutter. oh, I used 400 grit. but 280 would be fine also.
11-after you have one cyl. done, time to do a clay piston to valve measurement. I would do cyl. #1 both reliefs first, and do the clay testing before you bother cutting all the other cyl.s. I acutally cut too shallow the first time around, and had to go back and redo it all a second time. here's where some extra time spent will save you time in the long run. you can see here the depths I cut. that is not the clearance the valves have. I only wrote that on the piston to remind myself for later how deep I made the cuts. I set the clerance at .080" on intake side, and .100" on the exh. side. (actually I came in a tad MORE on the clearance due to using stock modified lifters that had the internals epoxied so the pushrod wouldnt compress the lifter plunger during my clearance tests, which would give me false readings. so I can add my preload to the actual clearances I measured for a true piston to valve spec). this time I used the stock head gasket for the measureing though since my real head is milled and I used the stock head gasket for mockup which is actually .014" thicker then what I'll use. so that means I need to take away .014" from the reading for true valve to piston clearance.
12-and here's the final result. notice how the exh. valve eyebrow on cyl. 3 here is larger/longer then the other (cyl. 1, 5, 7) exh. notches? thats cause I slightly messed that one up cutting it a tad too deep (or atleast deeper then I wanted to go). so as your working along, make sure all the cuts appear the same. the deeper the cut is, the wider the eyebrow will be. and you can notice a slight varience.
I hope this helps some people out there. wish my camera skills were as good or better then my mechanic skills so you could have beter pics, but my camera is touchy. doesnt like unnatural light. I had to take most of these pics several times as I went along to make sure I had a good clear pic when I was done.
also, dont forget to clean everything meticulously when your all done. youre gonna have to wipe off the piston, then lower the piston and wipe off the walls of the cyl. a couple times to make sure you dont have any metal bits between the piston/rings/and bore. that would be bad. then reoil the cylinders ofcourse when your all done. that consists of a thin layer of fresh oil wiped on the walls.
also #2, this is much easier with the eng/trans/kmember dropped out as seen in the pics. if you must do this with the eng. in the car, you'll need a 90deg. adapter for your drill. and some good back pain med.s for the next day.
but, I highly recomend dropping the eng. out for heads/cam/flycutting.
obviously this all needs to be done with max effort to keep the internal passages of the eng. clean. we'll start our instructions with the heads removed.
1- clean and cover everything.
2- find TDC with a dial indicator like so. there is a very slight pause at the top so watch for the needle to stop raising, pause, and start goin back down. watch the gauge carefully to see what the highest # seen is. also, notice how the tool is held in the same angle as the piston raises, and is on the middle of the piston where the wristpin is. if you had it at the 12 or 6 oclock positions, it would not be accurate due to the piston tilting in the bore.
3- tape off the complete block deck to keep the shavings from ending up anywhere else. on a side note, you need to try and get the head (tool) on in a way that the valves end up the same distance away from the block deck as the real head will be to try and best duplicate the correct valve angle. in my case, I milled .033" from my heads and used .040 cometics. so that adds up to the valves being .047" closer to the pistons then stock head/head gasket once its all together. the head I used for the tool was unmilled. so right there its .033" farther away then my new setup will be. so in an attempt to get the valves the same distance away from the piston to get the cut at the proper angle, I used 4 layers of blue tape to tape off the block which was right around .020" (I used a digi. mic, dont remember now if was 3 or 4 layers) and add the .033" more meat on the bottom of the head put me right around the proper placement. so I used 4 layers of tape and no head gasket to mock up the cutter. also you'll notice that I cut a window out of the tape in the middle of the piston where the notches will be. you'll see why in a minute.
4-here's what the "tool" looks like. some junk *** stock head with the int/exh. valve seats removed. the cutter slides up into the head in place of a valve. ::edit:: this is before I cut out the exh. seat.::edit::
5-after you have the block taped, and the window cut, apply some wD40 to the cutter and set the head in place and install 2 OLD head bolts. the bolt will pop right through the tape. just give it a pop with your hand. ligthly torque down the head bolts you just put in that are diag. across the cyl your working on. dont need much here, just tigten them up with a normal 3/8" ratchet good and tight. now, loosen up the lock collar and let the valve sit directly on the piston. the reason you wanted to cut the window out of the tape, is so your cuts are accurate, repeatable, and you know how deep they are. with the cutter sitting directly on the piston, collar loose, insert a feeler gauge between the top of the valve guide and below the locking collar. I cut my intakes to .120" deep. whatever you set this step up as, is how deep your cut will be IF you cut all the way down in the comeing up steps.pic 1 here is setting the cut depth with the feeler gauge's stacked to make up .120" total. pic 2 is how you lock down the collar with a very tiny allen wrench.
6- before you can start cutting, you need to take a measurement of the collar before and after you make the cut. this way, if the collar slips you'll know it. here's how I measured the collar position. note: this measurement was up to a few thousandths diff. from cyl. to cyl, due to the valve guide not being in the exact same placement in the head. so you'll have to measure each one to be sure. this is a small steel machinists ruler. see the top of the valve where it lines up with the 3/32" mark before I cut? and see the gap under the colar since this is before I made the cut?
7-now its finally time to make a cut. I used an air drill. but a keyless chuck would def. come in handy here. drill down slowly untill the collar is touching the valve guide. dont press hard though cause you dont want the collar to slip, ever. once you cut too deep, its done for. you'll be pulling atleast that piston for replacement. you can feel when the cutter is done cause it will freespin.
8-put the vacuum hose in the exh. port to remove the chips and "most" of the alum. dust. also helps to block off the intake port with your other hand to apply more vacuum. when cutting the exh. side (if you have to), put the vac. in the inake port instead to remove the bulk of material.
9-remove the head and then vac. the remaining pile of dust that was in the chamber ontop of the tape. next step is to measure the cut to make sure its as deep as you want it to be. you must clean out the cut though with a towel and parts cleaner. it should end up the depth you want. the corner of the feeler gauge should be flush with the middle of the eyebrow cut.
10- once your satisfied with the depth, then take a piece of sand paper and sand off the sharp edges from the cut. and clean off again with clean towel and parts cleaner. you can skip this step if your goin to cut the exh. side too, and sand/clean them both at the same time after you repeat all this for the exh. valve cutter. oh, I used 400 grit. but 280 would be fine also.
11-after you have one cyl. done, time to do a clay piston to valve measurement. I would do cyl. #1 both reliefs first, and do the clay testing before you bother cutting all the other cyl.s. I acutally cut too shallow the first time around, and had to go back and redo it all a second time. here's where some extra time spent will save you time in the long run. you can see here the depths I cut. that is not the clearance the valves have. I only wrote that on the piston to remind myself for later how deep I made the cuts. I set the clerance at .080" on intake side, and .100" on the exh. side. (actually I came in a tad MORE on the clearance due to using stock modified lifters that had the internals epoxied so the pushrod wouldnt compress the lifter plunger during my clearance tests, which would give me false readings. so I can add my preload to the actual clearances I measured for a true piston to valve spec). this time I used the stock head gasket for the measureing though since my real head is milled and I used the stock head gasket for mockup which is actually .014" thicker then what I'll use. so that means I need to take away .014" from the reading for true valve to piston clearance.
12-and here's the final result. notice how the exh. valve eyebrow on cyl. 3 here is larger/longer then the other (cyl. 1, 5, 7) exh. notches? thats cause I slightly messed that one up cutting it a tad too deep (or atleast deeper then I wanted to go). so as your working along, make sure all the cuts appear the same. the deeper the cut is, the wider the eyebrow will be. and you can notice a slight varience.
I hope this helps some people out there. wish my camera skills were as good or better then my mechanic skills so you could have beter pics, but my camera is touchy. doesnt like unnatural light. I had to take most of these pics several times as I went along to make sure I had a good clear pic when I was done.
also, dont forget to clean everything meticulously when your all done. youre gonna have to wipe off the piston, then lower the piston and wipe off the walls of the cyl. a couple times to make sure you dont have any metal bits between the piston/rings/and bore. that would be bad. then reoil the cylinders ofcourse when your all done. that consists of a thin layer of fresh oil wiped on the walls.
also #2, this is much easier with the eng/trans/kmember dropped out as seen in the pics. if you must do this with the eng. in the car, you'll need a 90deg. adapter for your drill. and some good back pain med.s for the next day.
but, I highly recomend dropping the eng. out for heads/cam/flycutting. Last edited by Irocss85; 05-06-2007 at 08:30 AM.
05-05-2007, 08:06 PM
#4
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its really not hard AT ALL. its not even really time consuming. i flycutt my pistons with the motor in the car using a wrench to turn the cutter and it still wasn't that bad.
i didn't read the writeup b/c I'm in a hurry right now, but good on you for trying to help out the community.
Jon
i didn't read the writeup b/c I'm in a hurry right now, but good on you for trying to help out the community.
Jon
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05-06-2007, 03:42 AM
#8
TECH Senior Member
I think you got it backwards on the intake and exhaust valves. The big ones are intake and the small ones are exhaust. You piston pick shows .120 (that is intake and .080 (that is exhaust).
would you like me to correct some of it and then sticky?
nice job BTW
would you like me to correct some of it and then sticky?
nice job BTW
05-06-2007, 08:23 AM
#10
no need for correction. you must have missed the part where I explained that those are not the clearances. those are the depths of the cut that I put on there so I would always remember how deep the cuts are.
I went back and tried to make that part more clear.
and thanks everyone for the comments.
I went back and tried to make that part more clear.
and thanks everyone for the comments.
Last edited by Irocss85; 05-06-2007 at 08:30 AM.
05-06-2007, 11:27 AM
#11
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Here's some info that helped me during my flycutting that may help others. I found it hard to have the tool in the head and measure the height of the collar and then use an allen key to tighten it in the right spot all at the same time. So what I did was, I used my micromoeter and found a washer that mic'd .080" that was only a tad bigger than the collar and I cut a notch out of it so that I could slide it in between the collar and the base of the valve guide to hold the collar up as I tighten it to the tools shaft, and then could slide it out for cutting after the collar was tight.
Also, I did my flycutting IN the car, so as you can imagine its hard to find anything to spin the tool around on the rear most cylinders that are under the windshield. Sure you could turn it by hand, but that takes forever.
I went to the hardware store and bought a tool called a "Gator Grip" (im sure there are other knock offs of it with different or similar names) For those who dont know what it is, Its basically a socket that is advertised to fit on any mis-shaped bolt/nut whatever. It has several spring loaded pins inside the socket head and will contour itself any shape.
I placed it on an air ratchet and this worked perfect for grabbing the shaft of the tool anywhere I could get it on in such a tight space.
Figured I would add this cause I had to come up with this myself and it took a few days of running around and trying different things before I got to this point so If I would have heard it somewhere else it would of saved me a couple days. Not to mention save someone from having to turn them by hand!
Hope this helps, I'll try to get pictures of the tool and the washer I modified to give everyone a better Idea.
Also, I did my flycutting IN the car, so as you can imagine its hard to find anything to spin the tool around on the rear most cylinders that are under the windshield. Sure you could turn it by hand, but that takes forever.
I went to the hardware store and bought a tool called a "Gator Grip" (im sure there are other knock offs of it with different or similar names) For those who dont know what it is, Its basically a socket that is advertised to fit on any mis-shaped bolt/nut whatever. It has several spring loaded pins inside the socket head and will contour itself any shape.
I placed it on an air ratchet and this worked perfect for grabbing the shaft of the tool anywhere I could get it on in such a tight space.
Figured I would add this cause I had to come up with this myself and it took a few days of running around and trying different things before I got to this point so If I would have heard it somewhere else it would of saved me a couple days. Not to mention save someone from having to turn them by hand!
Hope this helps, I'll try to get pictures of the tool and the washer I modified to give everyone a better Idea.
05-06-2007, 06:35 PM
#13
predator, what do you mean open for modification? just curious. just as in not locked?
anubis, great idea on the air ratchet. but two things. one, the problem with making a shim to put in there is that as I pointed out the guides are not all exactly the same heights. in my case, they wre mostly the same, but a few of them were a few thou. higher, creating shallower cuts if I would have just measured and put the coller to the same place each time.
and two, wondering how you had a hard time measureing the distance (or setting up the depth of the cut) with the feeler gauge? the cutter will hold it self down on the piston all by itself (gravity), then you set your feeler gauge between the collar and guide, and hold down the colar with one hand and tighten the screw with the other hand. do you mean you had trouble squishing the feelergauge with the lock collar or were you trying to measure a diff. way then I did?
anubis, great idea on the air ratchet. but two things. one, the problem with making a shim to put in there is that as I pointed out the guides are not all exactly the same heights. in my case, they wre mostly the same, but a few of them were a few thou. higher, creating shallower cuts if I would have just measured and put the coller to the same place each time.
and two, wondering how you had a hard time measureing the distance (or setting up the depth of the cut) with the feeler gauge? the cutter will hold it self down on the piston all by itself (gravity), then you set your feeler gauge between the collar and guide, and hold down the colar with one hand and tighten the screw with the other hand. do you mean you had trouble squishing the feelergauge with the lock collar or were you trying to measure a diff. way then I did?
05-07-2007, 04:48 PM
#15
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Originally Posted by Irocss85
predator, what do you mean open for modification? just curious. just as in not locked?
anubis, great idea on the air ratchet. but two things. one, the problem with making a shim to put in there is that as I pointed out the guides are not all exactly the same heights. in my case, they wre mostly the same, but a few of them were a few thou. higher, creating shallower cuts if I would have just measured and put the coller to the same place each time.
anubis, great idea on the air ratchet. but two things. one, the problem with making a shim to put in there is that as I pointed out the guides are not all exactly the same heights. in my case, they wre mostly the same, but a few of them were a few thou. higher, creating shallower cuts if I would have just measured and put the coller to the same place each time.
Also, if relying on the collar, be aware that pressing down hard on the cutting tool, you can easily push the piston down in the bore a little, which screws up your collar height. With the heads off, the engine rotates very freely.
I only used the collar for the first couple cuts, then found it quicker and easier just doing it by sight and feel. As you noted, you can easily tell the depth of the cut by how wide the eyebrow is. Trying to tighten that tiny collar set screw at each cut was more of a time waster than just cutting, then lifting the head off and checking. By the last few cuts, I had the feel of the cut pretty well down and was doing them in one try.
I also used an air ratchet for the cutting. According to Isky, the cutter is actually designed to be used by hand, not power. A drill is overkill, and could easily break or chip the relatively fragile cutting teeth. An air ratchet turns slower, and slips under high torque loads, so it's much more forgiving to both the tool, and your pistons. It's also about the most compact 90* tool you'll find, which lends itself well for doing this with engine in car.
Finally, one thing not mentioned that I learned when doing this, is that the cutter tends to bite and bind up hard when the cut is first started. The first couple revolutions are a bitch. I found running the cutter backwards (CCW) just to get the initial cut started helped a lot with this issue. Once the cut was started, then spinning it forward (clockwise) would work good with little or no binding.
I cut mine for intake only to .100" deep.
Great writeup!
05-07-2007, 06:47 PM
#16
Originally Posted by Thimble
I made a .100" shim exactly as described. It's no different than using a feeler gauge to set the collar. A feeler gauge is a material of a known thickness, and as explained, so is the shim. Set the cutter on the piston, insert shim on top of guide, drop collar down, tighten, remove shim, and cut. Valve guide length variation would make no difference...it will still only allow the cutter to drop until the collar hits the guide, and you shimmed your thickness between those two points.
Great writeup!
Great writeup!
yeah, you guys are totally right. I just wasnt thinking of this in my head right. the part I got mixed up (since this was like 3 months ago I did mine) was that my variation on a few valve guides left me with shallow cuts. those were the ones I had to go back and add a couple thou. cut depth to.
05-12-2007, 11:16 PM
#19
well, I rented one from LG motorsports. but its very expensive if you ask me. makes alot more sense to buy the cutters (they sell the cutters too) and a junk head and make your own. then sell it when your done. rent it out, whatever. it'll cost you about $220 for the two diam. cutters, the driveshaft for teh cutters, and the lockdown collar. plus the price of the head. if you rent one from LG or someother, you'll be paying $160 or $180 to rent it plus shipping charges.
05-13-2007, 06:24 AM
#20
Originally Posted by zeekracing
where do you get the cutter at?
http://www.lindytools.com/adjpiston.html
http://www.jayscarsite.homestead.com/files/cutter.JPG
http://www.jayscarsite.homestead.com...istonafter.JPG
http://www.jayscarsite.homestead.com/files/cutting.JPG
It's a big block but the theory still applies, notice I used a brand new head, I had to increase the diameter of the cut not the depth. Also if you're using heads with different valve angles you'll need to use the head you plan on running.