Piston Dome Dish and Compression Ratio
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Joined: Oct 2012
Posts: 214
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From: Sydne, NSW
I calculate with zero deck height compression will be 9.97 with 1.0mm head gasket. with factory .75mm gasket compression would be 10.20. shaving head .010in. would give 10.42.
the above calcs are with your 43.8cc chamber. dont know where you got that number? but factory size is 43cc. using 43cc the numbers go to 10.09, 10.31, and 10.55.
I dont add 1.5/2.0cc for area around top of ring land. that part of piston expands with heat. nearly touches cylinder wall under running conditions.
the above calcs are with your 43.8cc chamber. dont know where you got that number? but factory size is 43cc. using 43cc the numbers go to 10.09, 10.31, and 10.55.
I dont add 1.5/2.0cc for area around top of ring land. that part of piston expands with heat. nearly touches cylinder wall under running conditions.
Evolving Member
Joined: Jul 2011
Posts: 117
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From: Atlanta,Ga
Stock Evo 8 9 gasket is 1.18mm. According to Weisco it is 43cc this says http://rbid.ru/cr/ 43.8 Evo 4-9.
Thread Starter
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Joined: Oct 2012
Posts: 214
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From: Sydne, NSW
Spoke to David at head games he said he took 5thou off the head when he decked. So I need to know what dome cc I need to get 11:5:1 using a gasket of 1.2mm as it will be after market.
Last edited by JGNERAEVO9; Oct 24, 2013 at 12:46 PM.
The difference in power between the compression ratios you are talking about is likely to be nil.
No sense in cutting a block, head, or piston if it doesn't NEED it.
When you blow it up, you'll be glad you have that material next time around so you can fix the damage without buying a new block or head.
No sense in cutting a block, head, or piston if it doesn't NEED it.
When you blow it up, you'll be glad you have that material next time around so you can fix the damage without buying a new block or head.
Thread Starter
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Joined: Oct 2012
Posts: 214
Likes: 1
From: Sydne, NSW
Not looking to make more power per say looking to make the same power on less boost. Looking for a happy medium on a 76mm.
The difference in power between the compression ratios you are talking about is likely to be nil.
No sense in cutting a block, head, or piston if it doesn't NEED it.
When you blow it up, you'll be glad you have that material next time around so you can fix the damage without buying a new block or head.
No sense in cutting a block, head, or piston if it doesn't NEED it.
When you blow it up, you'll be glad you have that material next time around so you can fix the damage without buying a new block or head.
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