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To Fly Cut or Not to Fly Cut???

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Old 04-27-2011, 10:46 PM
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Default To Fly Cut or Not to Fly Cut???

I will be installing a cam in my '02 firehawk soon, its specs are 238/244-.605/.610- 114+4 with ported 202/157 - 243 heads, unmilled just cleaned.. My builder/tuner says it will be fine, what does anyone else think???
Old 04-27-2011, 10:58 PM
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Sounds REALLY close. I think you'll have to clay the piston to see what you have after it's installed.
Old 04-28-2011, 03:39 PM
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It might not hit but the ptv minimum will probably not be there. Are you going to use a .051 GM MLS head gasket?
Old 04-28-2011, 03:46 PM
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I'd get ready to flycut!
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Old 04-28-2011, 03:47 PM
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Originally Posted by getusumws6
It might not hit but the ptv minimum will probably not be there. Are you going to use a .051 GM MLS head gasket?
Forgive my ignorance but if thats what stock GM gaskets are then yes, thats what i had planned on using..
Old 04-28-2011, 04:01 PM
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i'd start making arrangements to cut. that being said you might as well mill and get your money's worth....
Old 04-28-2011, 04:02 PM
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TBH you are really going to need to test it out with clay. The lift isn't too extreme but with the duration you are looking at the transition from exhaust stroke to intake stroke will bite you in the ***. If it were a say 226/230 cam with the same lift you'd probably be close but safe.
Old 04-28-2011, 04:29 PM
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Originally Posted by Exidous
TBH you are really going to need to test it out with clay. The lift isn't too extreme but with the duration you are looking at the transition from exhaust stroke to intake stroke will bite you in the ***. If it were a say 226/230 cam with the same lift you'd probably be close but safe.
the lift has nothing to do with PTVC...
Old 04-28-2011, 04:44 PM
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Originally Posted by chrs1313
the lift has nothing to do with PTVC...
So. . . . what you're saying is the movement of the valves in relation to the movement of the piston is irrelevant? Granted timing is a part of this, but if the total movement of the valve can intersect with the total movement of the piston, then I would be concerned with PTV clearance...
Old 04-28-2011, 05:52 PM
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Originally Posted by chrs1313
the lift has nothing to do with PTVC...
I don't think nothing is the correct word. Maybe "is not the sole reason for PTVC issues"? A .490" lift I would image could allow a couple extra degrees of duration when compared to a .600" lift cam.
Old 04-28-2011, 06:53 PM
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Originally Posted by Exidous
I don't think nothing is the correct word. Maybe "is not the sole reason for PTVC issues"? A .490" lift I would image could allow a couple extra degrees of duration when compared to a .600" lift cam.
you are right I meant to have the "little" in there...


Originally Posted by Duffster
So. . . . what you're saying is the movement of the valves in relation to the movement of the piston is irrelevant? Granted timing is a part of this, but if the total movement of the valve can intersect with the total movement of the piston, then I would be concerned with PTV clearance...

where is the piston when the valve is at max lift...duration is the king along with split...
Old 04-28-2011, 07:08 PM
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Originally Posted by Matt@Texas-Speed
I'd get ready to flycut!
Do yall usually flycut for your PRC LS6 2.5 and MS3 combos?
Old 04-28-2011, 08:38 PM
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Default Hmmmm?

Well with all the controversy I will definitely be checking before final assembly. Since i dont know exactly what has been taken from the heads, it will be better to be safe than sorry, especially since so many people are on the edge or ARE recommending cutting... Thanks for the input!!
Old 04-29-2011, 09:36 AM
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Originally Posted by intenseblue
Do yall usually flycut for your PRC LS6 2.5 and MS3 combos?
If we setup the Stage 2.5 LS6's specifically for the MS3, we can make it comfortable to run, albiet still tight. But on your run of the mill ported LS6 head with 2.02"/1.57" valves, some random machine shop's valvejob, etc I will go ahead and bet the OP needs to flycut.
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Old 04-29-2011, 11:44 AM
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Originally Posted by Matt@Texas-Speed
If we setup the Stage 2.5 LS6's specifically for the MS3, we can make it comfortable to run, albiet still tight. But on your run of the mill ported LS6 head with 2.02"/1.57" valves, some random machine shop's valvejob, etc I will go ahead and bet the OP needs to flycut.
agreed, id be ready.



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