flycutting pistons strength questions?
TECH Resident
Joined: Apr 2008
Posts: 838
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From: Right here, right now!
Pistons with valve reliefs generally add material to maintain piston crown thickness under the reliefs. Plus flycutters generally dont leave a nice radius like a factory or aftermarket valve relief which drives up the stress profile considerably. Its a crap shoot. Minor flycuts like 0.30-0.40" will probably live within the factory engineering margin but the piston crown is not as fatigue resistant.
I ran .080 flycuts on my LS1 and currently have .060 on my LS2 without issues. I never used nitrous tho. The stock piston is either 220 or 250 thous thick there have been guys running flycuts exceeding 100 thous but that's pushing it IMO. The Lindy cutting does indeed provide a nice radius in the cut and is worth the money.
I am a self titled garage mechanic. I am a computer programmer by profession and schooling. I personally fly cut my pistons in my last vette, on an engine stand in my garage during december in chicago. It was freakin -10 and I had a space heater. I did it little by little by little, cause Ive never done it and I didnt want to ruin my motor. It was a low mileage LS6 short block. Long short, I sold the car to my buddy, and hes driving the HELL out of it 2 years later. Runs like a top, hes road raced it with me many times (5-6 30 minute sessions of 4000+ rpm, super hard on the car/motor). The car is starting out season 3 of flycut pistons, no excessive oil burn, no nada, and sincerely....he/I drive that car HARD. So I say do it, if a computer programmer can do it by himself in a garage and have zero issues in over 15k miles and 3 years, anyone can.
(no comments on nitrous though)
(no comments on nitrous though)
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On The Tree
Joined: Aug 2006
Posts: 107
Likes: 0
From: SW Virginia
I have 12:1 pistons which weigh a lot more than their 11:1 pistons, so I can weigh and also observe directly that they added more mass there.
I conclude I should be safe then having my engine builder machine some thousands off the top of the 12:1 to decrease my compression ratio. I was worried about upsetting the metallurgy or crystalline structure or something. I think I was getting too theoretical, but want to be careful.
I conclude I should be safe then having my engine builder machine some thousands off the top of the 12:1 to decrease my compression ratio. I was worried about upsetting the metallurgy or crystalline structure or something. I think I was getting too theoretical, but want to be careful.
We avoid it when possible. Run a combo that does not require it and call it a day. Problem is, for every success story there are many more failures and or mess ups. If you do not do it right, you can really screw yourself. Also, I have seen some flycut pistons actually develop hotspots which caused detonation.
Just my $0.02- if you do it, take your dam time and make sure you use a trash head you'll never use again.
Just my $0.02- if you do it, take your dam time and make sure you use a trash head you'll never use again.
I used the cutting tool from Lindy tools. It worked very well provided a clean well radius'd cut and .045 radial clearance . I used an old head as suggested above but have been told by more than one person they used their current heads with no ill effects.
Here are my 2.08 / .060 deep cuts on my intake side pic
Here is the cutting tool
Here are my 2.08 / .060 deep cuts on my intake side pic
Here is the cutting tool
