My90Iroc

iTrader: (26)

I'm looking to flycut my pistons a bit for added clearance. I have 2.04/1.57" valves (absolute speed) and when I measured the outer part of the valves they showed 2.14/1.67"
What size cutters should I use?
I can safely cut .050" into the pistons right? What's the limit?

Thanks.

SideStep

Here are the tools you want and I what I used:

(ThunderRacing)
91-PNT-214..Isky Piston Notching Tool, 2-1/4" Diameter......$124.99
91-NP-516....Isky Piston Notching Pilot, 8mm Valve Guide.....$39.99

The 2-1/8" tool is 2.125 and probably too small... .080 is the given maximum to cut... Some have done more.... Here is what you will end up with...

Teutonic Speedracer

iTrader: (20)

I plan on doing this tomorrow, .060" on the intake side. I have the 2-1/8 cutter coming with the 11/32" pilot. My valves are stock size though. The manufacturer has them on sale right now....pretty cheap!

GuitsBoy

iTrader: (4)

Brian, did we measure your valves as that big last weekend? I know I measured my stock valves and they were spot on at 2.00 and 1.55. I somehow doubt that these valves are actually larger than 2 1/8. I dont think those valves would fit in a stock bore, nor would the valves fit next to one another without overlapping seats.

I have heard that .100 was the limit but people have taken it out to .125.

Also, the fact that P to V minimum does not happen at TDC (where you do the cutting) affects two things. As the piston is partially down bore and the valve is opened , the valve is on a 15 degree angle which means the further down it extends, the further in towards the centerline of the piston the valve edge would be. Since we only car about the half moon shape, youre gaining clearance vs. the initial cutter size. The 2.04 inside a 2.125 flycut will gain side clearance as it travels down the bore. This however is a double edged sword. Since the valve is moving over laterally as it extends downward, the edge (lowest part of the valve) will be over a shallower part of the flycut. Gotta make sure you cut deep enough to compensate. A .050 deep flycut may only net you .025 extra clearance if at min p-v the valve edge is half way out of the eyebrow. This is compounded by using too larger a cutter, assuming you still cut .050 with a larger than needed cutter, even at TDC the valve edge will sit in a much shallower part of the releif.

Xtnct00WS6

iTrader: (8)

Is it possible to flycut with the engine in the car? Do people do this?

My90Iroc

iTrader: (26)

Thanks for the info.

Sidestep: I was going to flycut both the intake and exhuast for safety since I've been reading that the exhaust is just as much a concern (if not more) than the intake. The problem is that I'm on a stock bore and the 2 cutters sizes that would be big enough for my valves equal to 4" which is bigger than my bore.

Here's my setup, since I need advice:
AS 5.3 heads (valves seem to sit .030" lower than stock)
2.04/1.57" valves
comp X-ER 232/234 .595/.598" 112+4
.042 head gaskets
.003 surfacing to the heads for cleanup

SideStep

Yes, I did it and most people do...

GuitsBoy

iTrader: (4)

Again, I doubt that those valves are actually that large. But even if they were, youre not cutting inside the bore. The piston is at TDC, and due to the angle of the cutter, the outward edges are obove the deck of the block. As long as the heads are clearanced, youre fine.

marine02ss

iTrader: (3)

Nit hyjacking your tread,do I need to flycut with a F13 -114Lsa

GuitsBoy

iTrader: (4)

With stock heads? No, that cam will fit with plenty of room.

cantdrv65

iTrader: (3)

Hehe I have valve reliefs like those and didnt have to do any cutting at all....Just bust your timing chain at 6000 rpms or so....