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I am looking at an rb26 cylinder head for the rb30 twin cam head conversion.

I noticed that a place can do CNC head porting on the head, here are the flow figures,

FlowTest.jpg

Number 1 = modded intake

Number 2 = stock intake

Number 3 = modded exhaust

Number 4 = stock exhaust

I haven't seen any other figures to compare it with, if someone has them could they please let me know so I can compare.

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https://www.sau.com.au/forums/topic/284384-rb26-cnc-head-porting/
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Wow, that does look amazing ! Wonder how much they charge !!.

I have a word doc with all their prices etc it is not that unreasonable.

Interesting they remove or "condition" both pads in the combustion chamber.

I think you'll find that 1 is stock intake, 2 stock exhaust, 3 modified intake 4 modified exhaust. An RB exhaust will never outflow the intake except at very low lifts. Later Mitsubishi Evo heads do for part of the range though.

They're good numbers, That looks like Audie flow software, who is the head from?

I'm confident it would be @28".

You see above #1 it says CCFM, that is calculated cfm which with Audie software is either at 10" or 28" water and if the head is flowing those numbers at 10", multiply them by 1.67 to get flow @ 28" and you have a head that flows 511cfm @ 28" intake @ .5" and 392cfm on the exhaust at the same lift.

That's in the range that a 500cu/in pro stock head flows @ .8" lift and makes around 1300hp naturally aspirated @ over 9500rpm. On an RB26 it would have a sweet spot around 20,000ish rpm..

They are very good exhaust numbers, what sized valves is the head the data is from using?

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