317's
12-22-2009, 05:28 PM
#1
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317's ive been searching around and cant get a 100% straight answer. if i have a stock 1999 ls1 short block with stock pistons and i install a set of 317's what will my compression ratio be. i keep hearing different numbers and guys telling me that it "should be about" this number but i cant get a straight up solid repeatable number. HELP
how much do i have to mill them to get to 9.5?
did you guys buy them new or used and how much did you pay for a set?
how much do i have to mill them to get to 9.5?
did you guys buy them new or used and how much did you pay for a set?
12-22-2009, 07:47 PM
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I come up with 9.252 to 1 if you use head gaskets that are .051" thick and 4.065 bore. I'm assuming your pistons are .015" in the hole though. I think mine were close to .020" but my memory is fading fast!
If you need a set of 317s shoot me a pm. I ended up buying a set of Darts for my project so I have a pair sitting around.
If you need a set of 317s shoot me a pm. I ended up buying a set of Darts for my project so I have a pair sitting around.
12-22-2009, 08:00 PM
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ive been searching around and cant get a 100% straight answer. if i have a stock 1999 ls1 short block with stock pistons and i install a set of 317's what will my compression ratio be. i keep hearing different numbers and guys telling me that it "should be about" this number but i cant get a straight up solid repeatable number. HELP
how much do i have to mill them to get to 9.5?
did you guys buy them new or used and how much did you pay for a set?
how much do i have to mill them to get to 9.5?
did you guys buy them new or used and how much did you pay for a set?
what headgasket are you planning on using ?
where the heads milled ?
was the block ever decked ?
12-22-2009, 08:09 PM
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I used 3.898 for the bore size. Your bore size of your head gasket is always bigger and should be matched to the heads you are using and not the bore of the block. Otherwise you could be hanging the gasket into the combustion chamber of the head.
Frank
Frank
12-22-2009, 08:14 PM
#7
I used 3.898 for the bore size. Your bore size of your head gasket is always bigger and should be matched to the heads you are using and not the bore of the block. Otherwise you could be hanging the gasket into the combustion chamber of the head.
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12-24-2009, 07:35 AM
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You would need the heads to be 69cc to get 9.55. roughly every .005 you mill with give you 1cc so you would have to go .015" I would not reccomend milling the heads. The decks are thin enough as it is. I think 98 heads are 68cc. But they don't flow as well as 317s or 243s.