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Discussion Starter #1
oh PS if i do my HGs i'm gonna want to flycut the heads but i don't know much about this so if somone could fill me in (how much to cut, where to get it done, special procedures, prices, anyhitgn else) i'd appreciate it

have a good day,
James
 

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Discussion Starter #2
oh plus anything else that should be done at the same time
 

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Sheepish
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Flycutting notches the pistons for valve clearance in a high compression engine. Any automotive machine shop should be able to flycut a set of pistons. But when planning an engine, if you're going to be building a high compression motor, use clay on the piston crown or one of the cylinders and bolt a head on with an old gasket. Torque it down and slowly hand turn the motor, when you feel it lock up against the valve, turn it the other way so you can get a good reading on both intake and exhaust valves. You can do this yourself to determine how much clearance you need for your valves, or have the machine shop do it for you.
 

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Motorboatin' SOB, Headlight Cleaning Guru
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here's my 5.0 shortblock with flycut pistons. its also a good idea to get the pistons notched if you will be running a big duration cam.

 

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Flycutting is not specific to machining pistons....it's a machining process, using a certain type of tool. You can fly cut anything. If you read the original post, he's asking about cutting his heads, not his pistons.

As Mike said, valve reliefs in pistons have everything to do with piston to valve clearance due to agressive cam profiles and timing, decreased deck clearance, or even "pop-up" or domed pistons. Compression itself has nothing to do with it. Some of the things that people do to try to increase compression may result in decreased PTV clearance, such as a decked block, agressively machined heads to decrease combustion chamber volume, or dome pistons. But, you can run a long stroke motor that has 12.5:1 compression with flat top pistons and stock heads and not need valve reliefs in the pistons depending on your cam setup. Or, alternatively, you can run an engine with a low compression ratio, and require valve reliefs because of a very aggressive cam profile, or advanced cam timing.

Lazerviking - Just cut them enough to ensure flatness. Find a local speed shop. Or, some NAPAs have machine shops.

Mike
 

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Toombs said:
Flycutting is not specific to machining pistons....it's a machining process, using a certain type of tool. You can fly cut anything. If you read the original post, he's asking about cutting his heads, not his pistons.

As Mike said, valve reliefs in pistons have everything to do with piston to valve clearance due to aggressive cam profiles and timing, decreased deck clearance, or even "pop-up" or domed pistons. Compression itself has nothing to do with it. Some of the things that people do to try to increase compression may result in decreased PTV clearance, such as a decked block, aggressively machined heads to decrease combustion chamber volume, or dome pistons. But, you can run a long stroke motor that has 12.5:1 compression with flat top pistons and stock heads and not need valve reliefs in the pistons depending on your cam setup. Or, alternatively, you can run an engine with a low compression ratio, and require valve reliefs because of a very aggressive cam profile, or advanced cam timing.

Lazerviking - Just cut them enough to ensure flatness. Find a local speed shop. Or, some NAPAs have machine shops.

Mike
:zwthstpd:

What I've heard as the “common terminology” used in the "automotive world"(whether correct or not :leftright )
"Fly Cutting": Usually refers to cutting pistons for valve clearance
"Milling": Usually refers to truing/removing material from the heads or block.

Remember, if working with 4.6L stuff that there is a specific RA requirement on the heads and block unless you are going to use the aftermarket head gaskets. So make sure the machine shop knows what you’re talking about.

Just my .02. :thumbsup:
 
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