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Matto1kUte
What would be the compression ratio of an a12 with a10 pistons and h75 head?
#1
No life (a.k.a. DattoMaster)
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Hey all, just wondering what the compression ratio would be of an a12 with a10 flat top pistons and a stock h75 head? Trying to get around the 9.5-10:1 compression ratio. Would there be any valve clearance issues? Thanks

Posted on: 2022/1/9 13:35
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ddgonzal
Re: What would be the compression ratio of an a12 with a10 pistons and h75 head?
#2
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To achieve 10:1 - the stock A12 GX compression ratio - three things are necessary:

1. Flat-top pistons

2. extra-thin head gasket 0.8mm (Nissan 11044-H2301 GX gasket)

3. Combustion chambers of 29.1cc size (GX)


H89 can be blueprinted/skimmed to 29cc

H75: there are two H75 casting heads. One that is machined with open chamber (31cc). With standard 1.6mm head gasket will result in 8.8:1 compression ratio

With open chambers there is more run-on and detonation - even at lower compression ratios (ie. 8:5:1). More so at high CR. Reduce the spark timing to compensate. H89 head will not need this as it is closed chamber

Attach file:


jpg  11044-H2301 (with O-ring) Top.jpg (51.45 KB)
174_61db6370bcb85.jpg 1138X648 px

jpg  11044-H2301 Bottom.jpg (52.37 KB)
174_61db6436611e3.jpg 1138X648 px

jpg  11044-H2301 Head Gasket.jpg (29.51 KB)
174_61db643f50e30.jpg 600X450 px

Posted on: 2022/1/9 22:40
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Matto1kUte
Re: What would be the compression ratio of an a12 with a10 pistons and h75 head?
#3
No life (a.k.a. DattoMaster)
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Thankyou again :)

Posted on: 2022/1/11 17:02
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