Johny GTO

I spoke (by email) with a rep from livernois regarding their stage 3 LS6 heads. I was informed that with their stage 3 heads that fly-cutting of the pistons would be needed. I have never heard of this, i thought that people fly-cut pistons to clear the valves due to the timing on their cams.
can someone explain this for me?

edcmat-l1

iTrader: (10)

Their stage 3s probably have a 2.08 valve, and if they're milled to a small chamber size, you're gonna have PTV clearance issues.

Johny GTO

ahh ok. thanks.
so how hard is it to fly-cut? How much does it cost to have a shop do this? What are the downsides (if any) to having this done? Cost wise, does it just make more sense to buy new pistons?

edcmat-l1

iTrader: (10)

I tried flycutting with one of those in the head, on the car flycutters. I cut the second piston too deep, even though I was very careful to measure. I'm a stickler for measuring. Anyways, never again. The pistons come out and go to the machine shop. It aint worth my time dickin with it.

Johny GTO

just checked.... I dont see 2.08 valves.

New GM 243 casting
5 axis CNC machined
Fully assembled
220cc Intake Runner
Stainless 2.020 Intake Valves
Stainless 1.575 Exhaust Valves

Johny GTO

oh, and yeah i wouldnt do it myself. I would have someone do it. i have never seen a price on this though.

HEMIETR

iTrader: (2)

Some heads are designed with a different valve angle which will allow for more ptv clearence. The stock heads are 15* and TFS are 13.5*.

Bink

Milled heads??
The GMPP/LPE LS6 heads were milled .055" to bump up the CR ....59-60cc comb chamber. Moves the valves closer.
fwiw.

88ls1blazer

iTrader: (1)

I am assuming you were told you would have to notch because of the cam you were running in concert with the heads... Every manufacturer out there will (or should) say notching may be required. I shake my head everytime I see a thread about not having to notch with this combo or that combo. There are things called production tolerances that can make a combo have a good bit of clearance on one car, and another have not enough. I wonder how many people actually have .080 or more clearance like they are supposed to, or do they just roll the motor by hand, make sure it doesn't hit, and call it good?

There is a big difference between fitting, and having the proper clearance... One may cost you alot of money, the other will just cost you a little bit of time.

Here are some things to consider as well, The livernois heads are the best ported 243's I have ever touched, but their heads generally require the same clearance everyon's does, I would not dismiss their product because they are giving you cautious information. If given the choice between a company that errs on the side of caution when it comes to my car, versus one that pushes things past the limits, I will choose the open, honest, and cautious company EVERY time.

Johny GTO

Oh i am by no means dismissing their product. They are a great company with excellent rep that puts out a product that i have yet to hear one negative word about. When they told me about the fly-cutting, i thought maybe there was something i didnt know. Thanks for the thoughts.

gold98Z28

iTrader: (7)

on a combo that "should" not have ptv issues i just roll the engine over without the head gasket on to check for clearance, but if it is "close" or "questionalble" then i take more pains in measuring the PTV clearance

edcmat-l1

iTrader: (10)

Great post btw. I've seen many combos with a lack of sufficient ptv clearance. Did an L92 package that was already running, when we tore it down, it had .025 intake ptv. Talk about cutting it close.
As for what it costs to flycut pistons, we pay roughly 125 bucks to have them done.

WKMCD

iTrader: (2)

BTW: That wasn't mine.