milling 317 ?
Thread Starter
Joined: Aug 2008
Posts: 533
Likes: 1
From: South East AZ
milling 317 ? hey guys, got a couple questions, maybe you can help me.
what is the most i can mill a set of aluminum 317 heads?
how much do i need to mill to say achieve 65cc or even 63cc?
i have had a set forever now that i keep moving with me and they are just attracting dust. i bought them from a buddy of mine a couple years ago in the attempt to build a FI setup but the project never took it. i cant seem to sell them so im thinking that maybe im gunna build them. get a good port job on them, and a nice valvetrain and do a head swap down the road. that does sound more attainable then a 5 grand FI setup.
what is the most i can mill a set of aluminum 317 heads?
how much do i need to mill to say achieve 65cc or even 63cc?
i have had a set forever now that i keep moving with me and they are just attracting dust. i bought them from a buddy of mine a couple years ago in the attempt to build a FI setup but the project never took it. i cant seem to sell them so im thinking that maybe im gunna build them. get a good port job on them, and a nice valvetrain and do a head swap down the road. that does sound more attainable then a 5 grand FI setup.
Every .006 you take off is 1cc. So if you cut .030 off, that would drop the heads ~5cc but I think they're in the 72cc range in stock form, so you'd have to cut the **** out of them to achieve 63-65cc. Or cut .030, then run a thinner gasket.
Thread Starter
Joined: Aug 2008
Posts: 533
Likes: 1
From: South East AZ
alright thanx for the help. would cutting them .030 be safe enough to run. running the heads with that much milled, i would have to run 7.35" pushrods to maintain correct valvetrain geometry right?
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You can mill them .040 without having intake gasket sealing issues. If you did this and ran an 0.040 gasket you would have about 10.9:1 CR. Personally I would just ditch the 317's and pick up a set of 243/799 castings. If the 317's were already ported then it would be worth it to have them milled to work for you, but there are better options to start from scratch with.
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That is true, but at the point that you mill that much and run the thinner gasket you lose a lot of piston to valve clearance. So it also depends a lot on what cam you are looking to run. The 243 head will acheive the desired compression ratio without having to lose as much clearance so you can run a larger cam.
^^^^that is why^^^^. You are milling the heads as much as you can and running a thinner gasket to gain almost no compression over the stock heads. So I would not invest that much time and money into the 317 heads when there are much better options for a very reasonable price.
