Offshoreonly.com - Chamber porting for dropping compression

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Quote:

Originally Posted by rob vanharten (Post 4667978)

flat top with 3cc valve pocket.

You’re currently at 9.62 Cr by math assuming 4.63” head gasket. Your dead volume is 136cc, swept volume is 1172cc. You need 156cc to get down to 8.5cr. So you need to add 20cc.

Follow your head guy. He's amazing and always right. 25 plus years of personal knowledge of listening to him. He knows.

Quote:

Originally Posted by rob vanharten (Post 4667960)

Jason, I spoke with Jim on Saturday regarding my project. I am sitting around 9.8 right now and would like to get down in the 8.5-8.75 range. I understand this will not be doable with the porting alone but am hoping he can remove as much as possible while helping flow. I will still have to run thicker head gaskets but I am trying to run the thinnest gasket possible after the porting to get me to my desired compression ratio. Jim was thinking he could get them into the upper 120’s while increasing flow. I would be very happy with 10cc’s but a little more would be even better!!

Whatever Jim recommends is what I would do. We made almost 800 HP with 9.5 CR on pump gas