How many cc's will flycutting take out of pistons?

Vibrant93 · 07-03-2002, 07:05 PM

I am in the process of building an NA 347 and am running into a few delema situations. First off the car will have afr 205 heads which have 2.08 intake valves in them. Secondly I want to keep compression up in the 11.2:1 range and am finding that this is going to be a problem. The lightweight srp flat top pistions that I got have only 3cc reliefs in them which I assume will not be enough for any decent size cam and the 2.08" valves. Assuming I have the block set up with a zero deck and an 8548-pt2 head gasket this puts me at 11.278 with .020" taken off the afrs to bring them down to a 56cc chamber. So what I am wondering is about how many cc's on average does flycutting take out of a piston? I figure I may just have to use a thiner 1011-2 head gasket and or bring the piston .010" out of the hole. Am I going in the right direction here or are people running the afr 205's finding that they arent needing as big of valve reliefs as they thought they needed? Thanks for any input!

juiceman · 07-03-2002, 09:30 PM

its good that youre thinking about the workings of your motor but honestly, you dnt need to get into all that. the engine builder will tell you whether you need to fly cut or not. it is based on cam profile and piston location. as for the compression, dont get too intricate in that area. a 11.3 comp is not going to be any different than a 11.0 comp. there really isnt much hp gain in compression alone. but if youre going to get into it anyway then dont forget quench area. since you plan on bringing that piston closer to the head via thin gasket or decking the block you need to realize that you cant get too close to that head or you will run into problems. rods stretch under high rpm and valves float. the last thing you want is to crash that piston into a valve or worse the head.

Vibrant93 · 07-04-2002, 10:00 AM

Well since I am building the motor myself I really have no one to rely on for the answers here

I here ya on bringing the deck down thing, thats really something that I dont want to do but if I sit at zero deck and 56cc head chamer and assuming when I cut the pistons they will be at what, 6cc's, then I am now looking at 10.6:1 which Is just a bit lower than where I want to be with this n/a motor. So is it safe to say that by flycutting my pistons which have 3cc reliefs I will now be in the 6cc range? Just looking for an average of what others have found when they cut theirs.
thanks again

07-03-2002, 07:05 PM	#1
Vibrant93 Registered Member Join Date: Jul 2002 Posts: 2	How many cc's will flycutting take out of pistons? I am in the process of building an NA 347 and am running into a few delema situations. First off the car will have afr 205 heads which have 2.08 intake valves in them. Secondly I want to keep compression up in the 11.2:1 range and am finding that this is going to be a problem. The lightweight srp flat top pistions that I got have only 3cc reliefs in them which I assume will not be enough for any decent size cam and the 2.08" valves. Assuming I have the block set up with a zero deck and an 8548-pt2 head gasket this puts me at 11.278 with .020" taken off the afrs to bring them down to a 56cc chamber. So what I am wondering is about how many cc's on average does flycutting take out of a piston? I figure I may just have to use a thiner 1011-2 head gasket and or bring the piston .010" out of the hole. Am I going in the right direction here or are people running the afr 205's finding that they arent needing as big of valve reliefs as they thought they needed? Thanks for any input!

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07-03-2002, 09:30 PM	#2
juiceman Registered Member Join Date: Jan 2001 Location: ny Posts: 197	its good that youre thinking about the workings of your motor but honestly, you dnt need to get into all that. the engine builder will tell you whether you need to fly cut or not. it is based on cam profile and piston location. as for the compression, dont get too intricate in that area. a 11.3 comp is not going to be any different than a 11.0 comp. there really isnt much hp gain in compression alone. but if youre going to get into it anyway then dont forget quench area. since you plan on bringing that piston closer to the head via thin gasket or decking the block you need to realize that you cant get too close to that head or you will run into problems. rods stretch under high rpm and valves float. the last thing you want is to crash that piston into a valve or worse the head.

07-04-2002, 10:00 AM	#3
Vibrant93 Registered Member Join Date: Jul 2002 Posts: 2	Well since I am building the motor myself I really have no one to rely on for the answers here I here ya on bringing the deck down thing, thats really something that I dont want to do but if I sit at zero deck and 56cc head chamer and assuming when I cut the pistons they will be at what, 6cc's, then I am now looking at 10.6:1 which Is just a bit lower than where I want to be with this n/a motor. So is it safe to say that by flycutting my pistons which have 3cc reliefs I will now be in the 6cc range? Just looking for an average of what others have found when they cut theirs. thanks again