Just measured 2-
.039" and .038".
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| Compression ratio/head choice . https://www.ausmini.com/forums/viewtopic.php?f=2&t=81876 |
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| Author: | 1380 K [ Sun Jun 23, 2013 3:53 pm ] |
| Post subject: | Compression ratio/head choice . |
I am currently trying to figure out my compression ratio whilst my engine is apart. i am using this calculator http://www.csgnetwork.com/compcalc.html However it is asking for a head gasket compressed thickness which i can not find a spec for. |
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| Author: | drmini in aust [ Sun Jun 23, 2013 4:00 pm ] |
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Just measured 2- .039" and .038".
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| Author: | TheMiniMan [ Sun Jun 23, 2013 4:06 pm ] |
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yeah i always use .035" when calcing this stuff,,, it`s always more squashed than when it`s out of the car & also a little less vol in your calcs leaves you a little room for reality (on the safe side) |
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| Author: | 1380 K [ Sun Jun 23, 2013 4:18 pm ] |
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wow that was quick, cheers. So ive down these measurement as best as i can. Bore size: 73.5mm Piston stroke length:81.28mm Head gasket bore diameter:73.5 Compressed head gasket thickness:0.99mm Combustion chamber volume:21cc Piston dish volume -7cc Piston deck clearence0.3mm =11.3:1 Or my old head with combustion chamber of 23cc =10.7:1 This is on my weekend driver tuned 1380. Both heads are fairly standard (some might remember the drama from my purchase.) My old head however does not have double valve springs and im unsure if its got hardened valve seats. Trying to work out what one to use. Currently saving for graham russell to modify me a head but for now i have to use one of these. My new head also seems to have the valves deeper in the head than my old one. ill try get some pics. |
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| Author: | 1380 K [ Sun Jun 23, 2013 4:29 pm ] |
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Old head: 23cc 
New head: 21cc 
Sorry about photos being rotated |
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| Author: | 69k1100 [ Sun Jun 23, 2013 5:27 pm ] |
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Interesting the old head has been bath tubbed, which in itself is a performance modification. And the old head has life left in the seats and tapered valve guides. Why not get GR to suss them (pm?) |
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| Author: | 1380 K [ Sun Jun 23, 2013 7:10 pm ] |
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Yeah i beleive it was done to lower compression. Ill probably end up using the old one and possibly switch over the double valve springs onto it. Compression will be too hight otherwise. Maybe just go back to running valve saver just incase they arnt hardened seats. |
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