Author Topic: Fly cutting cast pistons  (Read 466 times)

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Offline stemp1

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Fly cutting cast pistons
« on: February 11, 2018, 04:49:01 PM »
What is the max for fly cutting Harley 103 cast pistons

Offline TorQuePimp

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Re: Fly cutting cast pistons
« Reply #1 on: February 11, 2018, 05:28:37 PM »
Max diameter valve or valve pocket ?

Offline stemp1

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Re: Fly cutting cast pistons
« Reply #2 on: February 11, 2018, 05:38:04 PM »
Valve pocket

Online Timinator

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Re: Fly cutting cast pistons
« Reply #3 on: February 12, 2018, 07:33:16 AM »
.030 and a about the same on the radius is safe. Make sure you have a nice radius on the flycutter too. That is where you can get into trouble, a sharp edge will cause a stress point there in the root of the cut. I usually go a bit larger radius than necessary to make sure I have that radius and valve clearance. Don't forget to radius the top of the cut too, not just for strength, but also for HP, while you're in there.
I also advise my customers that if you need a bigger valve notch, you usually need forged pistons, and I put that on the work order. Depending upon what the customer is building, I sometimes elect not to cut cast pistons for walk-ins or installation. Believe it or not, sometimes customers have been known to lie about their combination to get us to do things that we are smart enough to know shouldn't be done.
We have a few customers that like to push the envelope, but always take responsibility for their choices, we talk about what they are doing, and sometimes they see the light. One customer takes particular delight in doing the impractical, if it doesn't live, he adds the parts to his wall of knowledge. He is a retired gas turbine engineer, and has a clue, he just likes to "get away with things!"  TIMINATOR
MODESTY IS A CRUTCH FOR THE INCOMPETENT!!!

Offline HD Street Performance

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Re: Fly cutting cast pistons
« Reply #4 on: February 12, 2018, 02:30:09 PM »
You are .150 from the top of piston to the top of #1 ring land. Cut them the proper diameter radius and the depth you need. Very common and documented. ~.250 from piston edge. Was part of the essentials with the old HIPPO builds. Or just use cvo 103 pistons

Online sfmichael

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Re: Fly cutting cast pistons
« Reply #5 on: February 12, 2018, 02:55:12 PM »
You are .150 from the top of piston to the top of #1 ring land. Cut them the proper diameter radius and the depth you need. Very common and documented. ~.250 from piston edge. Was part of the essentials with the old HIPPO builds. Or just use cvo 103 pistons

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Colorado Springs, CO.

Offline TorQuePimp

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Re: Fly cutting cast pistons
« Reply #6 on: February 12, 2018, 09:04:38 PM »
I had to go dig my fly cutter out

1.963 od

My setup piston is a screaming eagle 103

If you know where the builds being tuned and customer isn't swinging for the fences I'd rather use cast