HOW TO "flycut pistons"
07-01-2007, 04:29 PM
#41
Originally Posted by Irocss85
like you thougth, just inside the deepest part of th eyebrow. Id say less the 1/8" in though. still very close to it.
Thanks for the input.
07-01-2007, 10:20 PM
#42
well I know the cars been runing now for a while, got around 800 miles on it, LOTS of high rpm blasts no problems yet. rev. limiter is set at 6700, and thanks to the factory POS tac being too slow to keep up with the engine, Ive hit the rev. limiter a few times already, so it appears I have plenty of clearance now. 
I just hope other people can learn from this and not be intimidated out of getting them cam they really want.
I just hope other people can learn from this and not be intimidated out of getting them cam they really want. 
07-08-2007, 08:18 AM
#46
didnt miss it. its impossible to have real definitions as to when its nec.. every combo will be different prety much. things like larger valves, longer durations cams, tight ICL timed cam (lower numericaly ie.110icl is tighter then 114icl, and will give less ptv clearance), decking the block, milling the heads, thinner head gaskets, all have an effect on how close the valve comes to the piston. its a good idea to check whenever you bring the valves closer to the piston then stock. just to be sure. the hasle it takes to take the measurements are nothing compared to buying a new engine.
08-13-2007, 05:57 PM
#47
Originally Posted by Irocss85
didnt miss it. its impossible to have real definitions as to when its nec.. every combo will be different prety much. things like larger valves, longer durations cams, tight ICL timed cam (lower numericaly ie.110icl is tighter then 114icl, and will give less ptv clearance), decking the block, milling the heads, thinner head gaskets, all have an effect on how close the valve comes to the piston. its a good idea to check whenever you bring the valves closer to the piston then stock. just to be sure. the hasle it takes to take the measurements are nothing compared to buying a new engine.
Bill
08-13-2007, 09:24 PM
#48
the general rule of thumb, is .080" intake valve and .100" for the exh. valve. you need more on the exh. valve due to it running alot hotter then the intake valve, and will grow with the heat. but, I talked with a handful of the big companies here about there clearance recomendations and the ones I talked to said you can get away with even tighter clearances than that. but overreving would be really bad then.
the best way to check it is with a dial indicater setup, a test lifter thats modified to be a solid lifter (I have some for sale BTW), and a degree wheel. then you can "map" the clearance. start at .020" before top dead center, and go in increments of .004" until you get to like 10degrees after top dead center. the cam I just tested (TII) the tightest spot was 4degrees after top dead center if I remember correctly. but that will be different for each cam. thats why you test every step through the large window. after you have the dial indicater and stand setup, taking the measurements only takes a few minutes. where it was closest, I tested every degree nearest.
the best way to check it is with a dial indicater setup, a test lifter thats modified to be a solid lifter (I have some for sale BTW), and a degree wheel. then you can "map" the clearance. start at .020" before top dead center, and go in increments of .004" until you get to like 10degrees after top dead center. the cam I just tested (TII) the tightest spot was 4degrees after top dead center if I remember correctly. but that will be different for each cam. thats why you test every step through the large window. after you have the dial indicater and stand setup, taking the measurements only takes a few minutes. where it was closest, I tested every degree nearest.
08-13-2007, 10:28 PM
#49
Originally Posted by Irocss85
the general rule of thumb, is .080" intake valve and .100" for the exh. valve. you need more on the exh. valve due to it running alot hotter then the intake valve, and will grow with the heat. but, I talked with a handful of the big companies here about there clearance recomendations and the ones I talked to said you can get away with even tighter clearances than that. but overreving would be really bad then.
the best way to check it is with a dial indicater setup, a test lifter thats modified to be a solid lifter (I have some for sale BTW), and a degree wheel. then you can "map" the clearance. start at .020" before top dead center, and go in increments of .004" until you get to like 10degrees after top dead center. the cam I just tested (TII) the tightest spot was 4degrees after top dead center if I remember correctly. but that will be different for each cam. thats why you test every step through the large window. after you have the dial indicater and stand setup, taking the measurements only takes a few minutes. where it was closest, I tested every degree nearest.
the best way to check it is with a dial indicater setup, a test lifter thats modified to be a solid lifter (I have some for sale BTW), and a degree wheel. then you can "map" the clearance. start at .020" before top dead center, and go in increments of .004" until you get to like 10degrees after top dead center. the cam I just tested (TII) the tightest spot was 4degrees after top dead center if I remember correctly. but that will be different for each cam. thats why you test every step through the large window. after you have the dial indicater and stand setup, taking the measurements only takes a few minutes. where it was closest, I tested every degree nearest.
Thanks,
Bill
08-13-2007, 11:06 PM
#51
Originally Posted by Xtnct00WS6
This is how I checked PTV clearance.
excellent.
only thing that method is I bet its hard to find ZERO lash w/o compressing the lifter plunger cause its VERY soft at the top of the travel. just make sure you feel for it several times and make sure that you ARE NOT COMPRESSING THE PLUNGER while tightening the rocker down or adj. the adj. pushrod till zero lash. that is a great little writeup though. if you have the heads off cause your swapping heads, then use the old head gasket and the new heads (prolly with larger valves then orig. and may be milled. so wont be same as stock heads) for mockup purposes. and a few old head bolts to tighten the head down around that cyl. for testing.
08-16-2007, 04:58 PM
#54
before I started this, I searched and couldnt find anyone that had a problem. then asked people what the max was they cut the depth to. one fella was at I think it was.140" AND used nitrous. think 150 shot. if it'll hold up to that, you'll be fine. oh, some shop told me the thickness was around .250" in that area of the dome. if I remember right.
08-16-2007, 05:22 PM
#56
no idea. but if I were ALREADY doin heads/cam and the customer also wanted that done, Id think $200 would be fair. it'll cost you around that much to do it yourself if you were to rent the tool's for doin it from one of our sponsors like I did this first time around. now I got a spare head set aside just for this.
chris
chris
08-17-2007, 10:59 AM
#58
ouch, not sure. that 112+4 part is what might push it over the edge. Id def. check the PtV clearance while its apart just to make sure. if i had to guess, Id say it'l clear, but not meet the safety margin.
Last edited by Irocss85; 12-25-2007 at 02:50 PM.
12-25-2007, 02:50 PM
#59
https://ls1tech.com/forums/generation-iii-internal-engine/832105-flycutting-tools.html
just thought Id add this is the tool Id buy instead of renting. wish I knew of this option when I did my flycutting cause I spent abot the same amount just to rent the tool.
but, now YOU know too.
chris
just thought Id add this is the tool Id buy instead of renting. wish I knew of this option when I did my flycutting cause I spent abot the same amount just to rent the tool.
but, now YOU know too.chris
